Class 10 Science SEE Guide | Unit - 4 Heredity Guide 2080

Class 10 Science SEE Guide

Unit - 4

Heredity Guide

( नेपालीमा उत्तर तल दिइएको छ )

Exercise

1. Choose the correct option for the given questions.

a. How many pairs of sex chromosomes are found in the human cell?

i. 1 pair

ii. 22 pairs

iii. 23 pairs

iv. 46 pairs

Answer 👉 iii. 23 pairs

b. What is a chromosome made up of?

i. DNA and RNA

ii. DNA and carbohydrate

iii. DNA and protein

iv. RNA and protein

Answer 👉 iii. DNA and protein

c. What is the main function of sex chromosomes?

i, To determine physical characteristics

ii. To determine sex

iii. To increase immunity

iv. To determine the structure of the eye

Answer 👉 ii. To determine sex

d. What is the smallest unit of the chromosome that helps in the transmission of hereditary characteristics?

i. DNA

ii. Chromatid

iii. Centromere

iv. Gene

Answer 👉 iv. Gene

e. Which of the following statements is correct for mitotic cell division?

i, Four cells are formed at the time of cell division.

ii. Haploid cells are formed at the end of cell division.

iii. It has the main role to form gametes.

iv. This cell division helps to repair tissue.

Answer 👉 ii. Haploid cells are formed at the end of cell division.

f. A technician working in a radiotherapy laboratory was tested after a long time of marriage when there was no childbirth. After the test, it was found that his child production capacity was reduced because he worked in high-intensity radiation for a long time. Which part of the cell is affected in this case?

i. DNA

ii. RNA

iii. Cytoplasm

iv. Nucleus

Answer 👉 i. DNA

g. If there is no DNA transcription in a cell, which process is affected?

i. Photosynthesis

ii. Protein synthesis

iii. Sexual reproduction

iv. Cell division

Answer 👉 ii. Protein synthesis

h. If a nucleotide is destructed during DNA replication, what happens to the organism?

i. Genetic disorder occurs

ii. It brings a problem in cell division

iii. It brings a problem in reproduction.

iv. The chromosome does not function.

Answer 👉 i. Genetic disorder occurs

i. Which of the following indicates the set of chromosomes in a cell of a woman?

i. 44+XY

ii. 44+XX

iii. 224XY

iv. 22+XY

Answer 👉 ii. 44+XX

j. Which of the following statements is true? :

i, Ovum contains only a Y chromosome and sperm contains an X chromosome.

ii. Ovum contains only an X chromosome and sperm contains aY chromosome.

iii. Ovum contains only an X chromosome and sperm contains either an X or Y chromosome.

iv. Ovum and sperm both contain X and Y-chromosomes.

Answer 👉 iii. Ovum contains only an X chromosome and sperm contains either an X or Y chromosome.

2. Write differences:

a. Autosome and sex chromosome

Answer 👉

Autosome:

Autosomes are non-sex chromosomes.
They are present in both males and females.
Autosomes determine the majority of an individual's traits and characteristics.
In humans, there are 22 pairs of autosomes.

Sex chromosome:

Sex chromosomes determine the sex of an individual.
In humans, there are two types of sex chromosomes: X and Y.
Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
The presence or absence of the Y chromosome determines the development of male or female traits.

b. Mitosis and meiosis

Answer 👉

Mitosis:

Mitosis is a type of cell division that occurs in somatic cells (non-reproductive cells).
The purpose of mitosis is to produce two identical daughter cells, each with the same number of chromosomes as the parent cell.
It is involved in growth, repair, and asexual reproduction.
Mitosis consists of one round of cell division and results in the formation of two diploid cells (2n).

Meiosis:

Meiosis is a type of cell division that occurs in reproductive cells (germ cells).
The purpose of meiosis is to produce gametes (sperm and eggs) with half the number of chromosomes as the parent cell.
It involves two rounds of cell division, resulting in four genetically unique haploid cells (n).
Meiosis is essential for sexual reproduction and contributes to genetic variation.

c. DNA and RNA

Answer 👉

DNA (Deoxyribonucleic acid):

DNA is a double-stranded molecule.
It contains the genetic information that determines the characteristics and traits of an organism.
DNA is found in the nucleus of cells.
It consists of nucleotides (adenine, thymine, cytosine, and guanine) and a sugar-phosphate backbone.
RNA (Ribonucleic acid):

RNA is a single-stranded molecule.

It plays a crucial role in protein synthesis and gene expression.
RNA is found in the nucleus and cytoplasm of cells.
It consists of nucleotides (adenine, uracil, cytosine, and guanine) and a sugar-phosphate backbone.
There are different types of RNA, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

d. Haploid and Diploid

Answer 👉

Haploid:

Haploid cells have half the number of chromosomes (n) compared to diploid cells.
They are gametes (sperm and eggs) in sexually reproducing organisms.
Haploid cells are produced through meiosis.
In humans, the haploid number is 23.

Diploid:

Diploid cells have a complete set of chromosomes (2n).
They are somatic cells in most multicellular organisms.
Diploid cells are produced through mitosis.
In humans, the diploid number is 46 (23 pairs of chromosomes).

3. Give reason:

a. Offspring have the same characteristics as their parents.

Answer 👉 Reason: Offspring inherit genetic information from their parents through the transmission of genes. Genes determine traits and characteristics, and they are passed down from parents to offspring. However, while offspring inherit genetic material from their parents, they may also undergo genetic recombination and mutations, which can introduce variations and result in differences between parents and offspring.

b. The male has a main role in the determination of sex.

Answer 👉 Reason: In mammals, including humans, sex determination is based on the presence or absence of the Y chromosome. Males have both X and Y chromosomes, while females have two X chromosomes. The presence of the Y chromosome in the sperm determines the development of male traits. Therefore, the male contributes the determining factor for the sex of the offspring.

c. Though males have both X and Y sex chromosomes, some of them have only male or only female kids.

Answer 👉 Reason: The sex of the offspring is determined by the combination of sex chromosomes received from both parents. While males have both X and Y chromosomes, they can pass on either an X or a Y chromosome to their children. If a male passes on an X chromosome, the offspring will be female (XX), and if a male passes on a Y chromosome, the offspring will be male (XY). Therefore, despite having both sex chromosomes, males can have either male or female children based on the chromosome they contribute during fertilization.

d. Meiotic cell division is also called reductional cell division.

Answer 👉 Meiotic cell division involves two rounds of division and results in the reduction of the chromosome number by half. During meiosis I, homologous chromosomes pair up and exchange genetic material through crossing over. This step separates homologous chromosomes, reducing the chromosome number from diploid (2n) to haploid (n). Meiosis II then separates sister chromatids, resulting in the formation of four haploid cells. The reduction in chromosome number is why meiotic cell division is referred to as reductional division.

e. Mitotic cell division is also called equational cell division.

Answer 👉 Reason: Mitotic cell division is a process by which a single cell divides into two genetically identical daughter cells. During mitosis, the replicated chromosomes are evenly distributed to the daughter cells, maintaining the same chromosome number as the parent cell. The daughter cells produced through mitotic cell division have the same genetic material as the parent cell, hence the term "equational division."

f. Sexual reproduction is impossible without meiotic cell division.

Answer 👉 Reason: Meiotic cell division is essential for sexual reproduction because it produces haploid gametes (sperm and eggs) with half the number of chromosomes as the parent cell. During fertilization, the fusion of a haploid sperm and a haploid egg restores the diploid chromosome number and results in the formation of a zygote. Without meiotic cell division, the production of haploid gametes would not be possible, and the combination of genetic material from two individuals would not occur, preventing sexual reproduction.

g Meiotic cell division brings variation.

Answer 👉 Reason: Meiotic cell division contributes to genetic variation in several ways. Firstly, during meiosis I, homologous chromosomes pair up and undergo crossing over, resulting in the exchange of genetic material between the chromosomes. This recombination introduces new combinations of genes, leading to genetic variation. Additionally, during meiosis I and II, the independent assortment of homologous chromosomes and sister chromatids creates further variation by randomly distributing different combinations of chromosomes and genetic information to the resulting haploid cells. As a result, meiotic cell division generates genetically diverse gametes, which contribute to the variation observed in sexually reproducing populations.

4. Answer the following question.

a. What is a gene?

Answer 👉 A gene is a segment of DNA (deoxyribonucleic acid) that carries the instructions for the synthesis of a specific protein or RNA molecule. Genes are the fundamental units of heredity and determine various traits and characteristics of living organisms. They are responsible for the transmission of genetic information from parents to offspring.

b. What is a chromosome? Clarify the role of chromosomes in the body of living beings.

Answer 👉 A chromosome is a thread-like structure made up of DNA and proteins. It carries the genetic information (genes) of an organism. Chromosomes are found in the nucleus of cells and are responsible for maintaining and transmitting genetic material during cell division and reproduction.

The role of chromosomes in the body of living beings includes:
Carrying genes: Chromosomes contain genes that determine various traits and characteristics of an organism, such as eye color, hair color, and height.
DNA packaging: Chromosomes help in the efficient packaging and organization of DNA molecules. They ensure that the long DNA molecules fit into the small nucleus of a cell.
Cell division: Chromosomes play a crucial role in cell division. During mitosis, chromosomes replicate and ensure that each daughter cell receives an identical set of chromosomes. During meiosis, chromosomes undergo recombination and sorting, resulting in the production of haploid gametes.

c. Explain the importance of mitotic cell division in the growth and development of the body.

Answer 👉 Mitotic cell division is important for the growth and development of the body because it allows for the increase in cell number and the formation of new tissues and organs. Some key points regarding the importance of mitotic cell division are:

Growth: Mitosis allows for the growth and development of an organism by increasing the number of cells. Through repeated rounds of mitosis, cells divide and multiply, leading to the development of tissues and organs
Tissue repair: When tissues are damaged due to injury or normal wear and tear, mitotic cell division helps in the regeneration and repair of those tissues. New cells are produced through mitosis to replace the damaged or dead cells.
Asexual reproduction: In some organisms, mitotic cell division is involved in asexual reproduction, where offspring are produced from a single parent without the involvement of gametes or fertilization.
Maintenance of chromosome number: Mitotic cell division ensures that the chromosome number remains constant in each generation. The replicated chromosomes are distributed equally between the daughter cells, maintaining the genetic stability of the organism.

d. Explain the role of mitosis and meiosis in the reproduction of organisms.

Answer 👉 Mitosis and meiosis play crucial roles in the reproduction of organisms.

Mitosis:

Mitosis is involved in asexual reproduction, where offspring are produced from a single parent without the involvement of gametes.
During mitosis, a single cell divides into two genetically identical daughter cells.
It helps in the growth, development, and tissue repair of an organism.
The daughter cells produced through mitosis have the same chromosome number as the parent cell, ensuring genetic stability.

Meiosis:

Meiosis is involved in sexual reproduction, where offspring are produced through the fusion of gametes.
It occurs in the reproductive cells (germ cells) of organisms.
Meiosis involves two rounds of cell division, resulting in the formation of four haploid cells (gametes) with half the number of chromosomes as the parent cell.
It introduces genetic variation through processes like crossing over and independent assortment of chromosomes.
During fertilization, the fusion of haploid gametes restores the diploid chromosome number in the offspring, combining genetic material from two parents.

e. What will happen if meiotic cell division does not occur in the reproductive cell of an organism? Explain.

Answer 👉 If meiotic cell division does not occur in the reproductive cell of an organism, several consequences would arise:

Failure to produce haploid gametes: Meiosis is responsible for the production of haploid gametes with half the number of chromosomes as the parent cell. Without meiosis, the reproductive cell would not undergo reductional division, resulting in the failure to produce gametes.
Lack of genetic diversity: Meiosis introduces genetic variation through processes like crossing over and independent assortment of chromosomes. Without meiosis, there would be no recombination of genetic material, and the offspring would inherit an identical set of chromosomes from the parent cell, leading to reduced genetic diversity.
Difficulty in sexual reproduction: Meiosis is essential for sexual reproduction, as it produces gametes that can fuse during fertilization to form a new organism. Without meiosis, the formation of haploid gametes would be disrupted, making sexual reproduction impossible or severely impaired.
Increased chromosome number: In sexually reproducing organisms, meiosis is crucial for maintaining the constant chromosome number from one generation to the next. Without meiotic cell division, the chromosome number would double with each generation, leading to an uncontrolled increase in chromosome number and disrupting the genetic stability of the organism.

f. Clearly explain the role of genes in the transmission of hereditary characteristics in organisms.

Answer 👉 Genes play a vital role in the transmission of hereditary characteristics in organisms. Some key points regarding the role of genes are:

Genetic information: Genes carry the instructions for the synthesis of specific proteins or RNA molecules. These instructions are encoded in the DNA sequence of the gene.
Inheritance: Offspring inherit genes from their parents. Genes are passed down from one generation to the next through reproductive cells (sperm and eggs) during sexual reproduction or through cell division in asexual reproduction.
Traits and characteristics: Genes determine various traits and characteristics of an organism, such as eye color, hair color, height, and susceptibility to certain diseases. Different combinations and variations of genes contribute to the diversity observed within a species.
Alleles and variations: Genes exist in different forms called alleles. Alleles can be dominant or recessive, and they contribute to the variations in traits among individuals. The specific combination of alleles inherited from both parents determines the phenotype (observable traits) of an organism.
Genetic expression: Genes are expressed through the synthesis of proteins or RNA molecules, which perform specific functions in the cells and contribute to the development and functioning of the organism.
Mutation and evolution: Mutations, which are changes in the DNA sequence of genes, can lead to variations in traits. Over time, these variations can accumulate and contribute to the evolution of species.

g. How is sex determined in humans? Explain with a chart.

Answer 👉 In humans, sex determination is based on the combination of sex chromosomes received from both parents. The chart below explains the sex determination in humans:

A female has two X chromosomes (XX).
A male has one X chromosome and one Y chromosome (XY).
During fertilization, the sperm contributes either an X or a Y chromosome to the offspring.
If an X-bearing sperm fertilizes the egg, the resulting offspring will be female (XX).
If a Y-bearing sperm fertilizes the egg, the resulting offspring will be male (XY).

Sex Chromosomes | Egg (X) | Egg (X)

Sperm (X) | Female (XX) | Female (XX)

Sperm (Y) | Male (XY) | Male (XY)

h. A woman is pregnant. What is her probability of giving birth to a daughter? Write in percent.

Answer 👉 The probability of giving birth to a daughter is 50% or 0.5. This is because the determination of the child's sex depends on the sperm that fertilizes the egg. If an X-bearing sperm fertilizes the egg, a female (daughter) will be conceived, and if a Y-bearing sperm fertilizes the egg, a male (son) will be conceived. Since the father can contribute either an X or a Y chromosome, there is an equal chance for the sperm carrying an X chromosome or a Y chromosome to fertilize the egg, resulting in an equal probability of having a daughter or a son.

i. A couple gave birth to only a son. Does it mean that the testes of those male-produced sperm have Y-chromosomes only?

Answer 👉 No, the fact that a couple gave birth to only a son does not necessarily mean that the testes of those males produced sperm with Y-chromosomes only. The sex of the offspring is determined by the combination of the sperm and egg during fertilization. The male parent contributes both X and Y chromosomes in his sperm, while the female parent contributes one X chromosome in her egg. The sex of the offspring depends on which sperm fertilizes the egg.

In the case of giving birth to only a son, it means that the sperm carrying a Y chromosome from the father fertilized the egg from the mother, resulting in a male child. However, the male parent can still produce sperm carrying an X chromosome, which could result in the birth of a daughter if that sperm fertilizes the egg. The sex of the offspring is determined by chance and the specific sperm and egg combination during fertilization.

4.8 Genetics and genetic technology

Exercise

1. Choose the correct option for the following questions.

a. What plant did Mendel use for his experiment?

i. Pea

ii. Gram

iii. Maize

iv. Bean

Answer 👉 i. Pea

b, Which of the following is the genotypic ratio for Monohybrid cross?

i. 12

ii. 31

iii, 1:2:2

iv. 9:2:31

Answer 👉 iv. 9:2:31

c. What is the term for a characteristic that is passed down from generation to generation? |

i. Dominant character

ii. Recessivecharacter

iii. Hereditary character

iv. Imported character

Answer 👉 iii. Hereditary character

d. A white-skinned child was born to a dark-skinned parent. What is the reason for this?

i. The parent was hybrid

ii. Both the father and mother have pure black characters

iii. White colour is dominant

iv. Black colour is recessive

Answer 👉 iii. White colour is dominant

e. In order to produce good meat, farmers look for Boer goats and cross them with local goats. What kind of breeding method is this?

i. Artificial insemination

ii. Selective breeding

iii. IVF

iv. Natural selection

Answer 👉 ii. Selective breeding

f. Ramit has produced a new plant by crossing an orange plant and a lemon plant.What type of plant is this?

i. Advanced variety of plant

ii. Pure plant

iii. Hybrid plant

iv. Artificial plant

Answer 👉 iii. Hybrid plant

g Roshaniisastudent from the Himalayan region. A mule is reared in her home for transportation of the goods. But the mule is getting older, and her family members are considering getting a new mule. In this situation, she asked her father how an amulet gives birth to a child. Which of the following is the correct answer given by her father?

i, Mules produce offspring naturally

ii. There is inbreeding in mule.

iii. Mule cannot produce offspring naturally

iv. Mules produce offspring by Al

Answer 👉 iii. Mule cannot produce offspring naturally

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2. Differentiate:

i. Dominant and recessive characters

Answer 👉 Dominant characters refer to traits or characteristics that are expressed or observed when present in an individual's genotype. They mask the expression of recessive characters. In a pair of alleles (variants of a gene), the dominant allele is represented by a capital letter (e.g., "B"), while the recessive allele is represented by a lowercase letter (e.g., "b"). Dominant characters are expressed in the phenotype when present in either homozygous dominant (BB) or heterozygous (Bb) genotypes, whereas recessive characters are only expressed in the phenotype when present in a homozygous recessive genotype (bb).

ii. Phenotype and genotype

Answer 👉 Phenotype refers to the observable physical and biochemical traits or characteristics of an individual, which are the result of the interaction between the genotype and the environment. It includes features like eye color, hair type, and height. Genotype, on the other hand, refers to the genetic makeup or the combination of alleles present in an individual's DNA. It represents the specific genes and alleles an individual possesses, which may or may not be expressed in the phenotype. While the phenotype is observable, the genotype is not directly visible but can be inferred through genetic testing.

iii. Inbreeding and crossbreeding

Answer 👉 Inbreeding is a breeding method in which closely related individuals, such as siblings or parent-offspring, are bred together. It leads to a reduction in genetic diversity within a population and increases the likelihood of expressing recessive genetic disorders. Inbreeding can also lead to the fixation of favorable traits or the accumulation of harmful traits.

Crossbreeding, also known as outbreeding, is a breeding method that involves mating individuals from different breeds or populations. It aims to combine desirable traits from different genetic backgrounds and increase genetic diversity. Crossbreeding can result in offspring with improved characteristics such as higher productivity, disease resistance, or specific traits desired by breeders.

iv. Artificial insemination and invitro fertilization

Answer 👉 Artificial insemination is a reproductive technique in which semen, collected from a male, is introduced into a female's reproductive system through assisted means. It involves the direct placement of sperm into the reproductive tract of a female, bypassing natural mating. Artificial insemination is commonly used in animal breeding programs to control and improve genetic traits.

In vitro fertilization (IVF) is a fertility treatment technique used in human reproduction. It involves the retrieval of eggs from the female and the fertilization of those eggs with sperm in a laboratory setting, outside the woman's body. The resulting embryos are then transferred back into the woman's uterus for implantation and pregnancy. IVF is often employed in cases of infertility or when traditional methods of conception are not successful.

v. Tigon and Liger

Answer 👉 Tigon and liger are both hybrid big cat species resulting from the crossing of different members of the Panthera genus:

Tigon: A tigon is the offspring of a male tiger and a female lion. The male tiger contributes the sperm, while the female lion provides the egg. Tigons have physical characteristics resembling both tiger and lion traits, but they are usually smaller in size compared to their parents. Tigons are relatively rare, as tigers and lions inhabit different regions and their breeding in the wild is uncommon.

Liger: A liger, on the other hand, is the offspring of a male lion and a female tiger. The male lion contributes the sperm, while the female tiger provides the egg. Ligers are known for their large size, as they can exhibit growth patterns that are influenced by the genetic factors of both lion and tiger species. They have a combination of physical characteristics from both parent species.

It's important to note that tigons and ligers are examples of hybrid offspring that do not occur naturally in the wild. They are typically found in captivity or as a result of controlled breeding programs.

3. Give reason:

a. Children look like their parents, but not exactly the same.

Answer 👉 Reason: Children inherit genetic material from both their parents, which contributes to their physical traits. However, genetic variation occurs due to the combination of genes from both parents, resulting in differences in traits among individuals, even within the same family. Additionally, environmental factors can also influence the expression of certain traits, leading to further variations.

b. Mendel selected pea plants for his experiment.

Answer 👉 Reason: Mendel selected pea plants for his experiments because they possess several advantages for studying inheritance patterns. Pea plants have easily distinguishable traits, such as flower color, seed shape, and plant height, which allowed Mendel to track the inheritance of specific characteristics through generations. Pea plants also have a relatively short reproductive cycle and produce a large number of offspring, facilitating statistical analysis and the observation of inheritance patterns.

c. When tall pea plants and dwarf pea plants are cross- pollinated, tall plants are produced in the first filial generation.

Answer 👉 Reason: In pea plants, the height trait is controlled by a pair of alleles, with the allele for tallness (T) being dominant over the allele for dwarfness (t). When tall plants (TT) are cross-pollinated with dwarf plants (tt), all the offspring in the first filial generation (F1) will inherit one copy of the dominant allele (T) from the tall parent, resulting in them being tall (Tt). Since the dominant allele masks the expression of the recessive allele, only the dominant trait (tallness) is observed in the F1 generation.

d. When self-breeding is done between hybrids, different types of offspring are produced.

Answer 👉 Reason: Hybrids are the result of the crossbreeding between individuals with different genetic backgrounds. When these hybrids self-breed, their offspring will inherit a mixture of genetic material from both parent lines. Due to the recombination and segregation of alleles during gamete formation, different combinations of traits can arise in the offspring. This variation in genetic material can lead to the expression of different types of offspring with diverse phenotypes and genotypes.

e. DNA testing is a reliable technique for criminal investigation.

Answer 👉 Reason: DNA testing is a highly reliable technique for criminal investigation due to the unique and stable nature of DNA. Each individual's DNA profile is distinct, except for identical twins. By analyzing DNA samples found at crime scenes and comparing them with DNA samples from potential suspects, forensic scientists can determine if there is a match. The accuracy and reliability of DNA testing have been extensively validated and proven through scientific research and forensic casework, making it a powerful tool in criminal investigations.

f. Genetic engineering involves the detailed study of DNA.

Answer 👉 Reason: Genetic engineering is a field of biotechnology that involves manipulating the genetic material (DNA) of organisms to introduce specific traits or modify existing ones. In order to manipulate and engineer DNA, a detailed understanding of its structure, function, and regulatory mechanisms is necessary. Genetic engineers analyze and study DNA sequences, genes, and their interactions to identify specific genes of interest, modify them, and transfer them into other organisms. This knowledge of DNA enables scientists to make precise modifications and create genetically modified organisms with desired traits.

g Offspring produced by cross-breeding may be sterile.

Answer 👉 Reason: In some cases, when individuals from different species or closely related species are crossbred, the resulting offspring may be sterile or have reduced fertility. This is known as hybrid sterility or hybrid infertility. It occurs due to genetic incompatibilities between the parental species, which can lead to abnormal reproductive development or impaired gamete formation in the hybrids. As a result, the hybrids may not be able to produce viable offspring, contributing to the reproductive isolation between the parental species.

h. Special attention should be given while collecting samples for DNA testing.

Answer 👉 Reason: Collecting samples for DNA testing requires careful attention to ensure accurate and reliable results. DNA samples can be easily contaminated, degraded, or lost during collection, handling, and storage. Therefore, special precautions should be taken to minimize the risk of contamination and ensure the integrity of the samples. Proper sterilization techniques, protective clothing, and sterile collection tools may be necessary to prevent the introduction of foreign DNA. Additionally, appropriate storage conditions, such as low temperature or the use of preservatives, may be required to maintain the stability of the DNA samples until analysis. By following proper collection protocols, the risk of sample contamination or degradation can be minimized, leading to more accurate and reliable DNA test results.

4. Answer the following question:

a. What is genetics?

Answer 👉 Genetics is the branch of biology that studies how traits and characteristics are passed down from parents to offspring. It involves the study of genes, heredity, and variation in living organisms. Genetics explores the structure and function of genes, as well as the mechanisms of inheritance and the patterns of genetic traits in populations.

b. What is DNA testing? For what purposes is it used?

Answer 👉 DNA testing, also known as DNA profiling or genetic testing, is a laboratory technique used to analyze an individual's DNA (deoxyribonucleic acid) sample. It involves examining specific regions of DNA to identify variations or markers that can provide information about a person's identity, genetic relationships, or predisposition to certain genetic disorders. DNA testing is used for various purposes, including paternity testing, forensic identification, genealogical research, diagnosing genetic disorders, and assessing genetic predispositions for personalized medicine.

c. Give some examples of genetic technology.

Answer 👉 Some examples of genetic technology include:

Genetic engineering: Manipulating an organism's DNA to introduce new genes or modify existing ones, leading to the production of genetically modified organisms (GMOs) with desired traits.
Polymerase Chain Reaction (PCR): A laboratory technique used to amplify a specific DNA segment, allowing for the detection and analysis of small amounts of DNA.
Gene therapy: Modifying or replacing defective genes in individuals with genetic disorders to treat or prevent the disease.
DNA sequencing: Determining the precise order of nucleotides in a DNA molecule, enabling the identification of genetic variations and the study of genomic information.

d. Mention the importance of DNA in genetic technology.

Answer 👉 DNA is of paramount importance in genetic technology due to its role as the carrier of genetic information. DNA contains the instructions necessary for an organism's growth, development, and functioning. In genetic technology, DNA serves as the target for manipulation, analysis, and understanding of genes and their functions. Techniques such as DNA sequencing, PCR, and genetic engineering rely on the accurate detection, extraction, and manipulation of DNA to study genetic traits, diagnose disorders, create genetically modified organisms, and develop new treatments.

e. Explain the importance of genetic engineering.

Answer 👉 Genetic engineering plays a crucial role in various fields and has significant importance:

Agriculture: Genetic engineering allows the development of crops with improved traits, such as increased yield, resistance to pests, tolerance to environmental conditions, and enhanced nutritional value.
Medicine: Genetic engineering enables the production of therapeutic proteins, development of gene therapies, and advancement in the understanding and treatment of genetic disorders and diseases.
Environmental applications: Genetic engineering can contribute to environmental sustainability by creating organisms capable of cleaning up pollutants, producing biofuels, or reducing the use of harmful chemicals in agriculture.
Industrial applications: Genetic engineering facilitates the production of enzymes and microorganisms for industrial processes, such as the production of biofuels, pharmaceuticals, and biodegradable plastics.

f. What is a monohybrid cross? Show in the filial chart, the result obtained by cross-pollinating first and then self-pollinating of a red flowering pea plant and a white flowering pea plant.

Answer 👉 A monohybrid cross is a genetic cross between two individuals that differ in a single trait. In this case, the cross is between a red flowering pea plant (RR genotype) and a white flowering pea plant (rr genotype).

Filial Chart:

Parental generation: RR (red flowering) x rr (white flowering)

Punnett Square:

r | Rr | Rr |

Resulting offspring in the first filial generation (F1): All offspring will have the genotype Rr and exhibit the phenotype of red flowering.

g Explain with an example that Mendel's experiment can be done not only in plants but also in animals.

Answer 👉 Mendel's experiment on inheritance patterns can be applied to animals as well. One example is the study of coat color in mice. Similar to Mendel's experiments with pea plants, researchers can cross mice with different coat colors and observe the inheritance patterns in their offspring. For instance, when a black-coated mouse (BB genotype) is crossed with a white-coated mouse (ww genotype), the F1 generation will have all black-coated offspring (Bw genotype). By conducting further crosses and analyzing the subsequent generations, researchers can observe the segregation of traits and determine the underlying genetic principles, just as Mendel did with his experiments on pea plants.

h. Explain the Mendel's law of dominance and purity of gametes.

Answer 👉 Mendel's law of dominance states that in a cross between individuals with contrasting traits, only one of the traits will be expressed in the offspring, known as the dominant trait, while the other trait remains hidden, known as the recessive trait. The dominant trait masks the expression of the recessive trait in the heterozygous condition.

Mendel's law of purity of gametes, also known as the law of segregation, states that during gamete formation, the two alleles for a trait separate or segregate from each other, so that each gamete carries only one allele. This ensures that when gametes combine during fertilization, each parent contributes one allele for each trait to the offspring.

j. When a cross is made between a black guinea pig and a white guinea pig, the offspring of first filial generation were all black. Explain why white guinea pigs did not appear in this generation?

Answer 👉 In this case, the black guinea pig is most likely homozygous dominant (BB genotype) for coat color, and the white guinea pig is homozygous recessive (bb genotype). According to Mendel's law of dominance, the dominant trait (black coat color) masks the expression of the recessive trait (white coat color). When these two individuals are crossed, all the offspring in the first filial generation (F1) will inherit one dominant allele from the black parent (Bb genotype), resulting in a black coat color. Since the white guinea pig is homozygous recessive, it does not possess a dominant allele to contribute to the offspring's genotype, and thus, white guinea pigs do not appear in the F1 generation.

k. A teenage girl who has lost her mental balance became the victim of rape and gave birth to a child. How can the father of the child be detected?

Answer 👉 In cases where the father of a child needs to be determined, DNA paternity testing can be performed. DNA samples are collected from the child, the mother, and the alleged father. The DNA profiles of these individuals are analyzed to compare specific regions of their DNA, including highly polymorphic genetic markers. If the alleged father is indeed the biological father, the child's DNA will share specific genetic markers with the alleged father that are not present in unrelated individuals. By comparing the DNA profiles, scientists can establish whether the alleged father is the biological father of the child with a high degree of accuracy.

l. The district animal development centre conducted a camp to fertilize many cows at once. Which technique did that organization adopt at that time? Explain this technique in brief.

Answer 👉 The technique that the district animal development centre most likely adopted is artificial insemination (AI). Artificial insemination involves the collection of semen from a male animal and the subsequent introduction of the semen into the reproductive tract of a female animal, bypassing natural mating. In the case of the camp conducted by the centre, they aimed to fertilize many cows at once, indicating a large-scale breeding program. By utilizing AI, the centre can ensure controlled breeding, select superior male donors for semen collection, and distribute the semen to multiple female cows, thereby improving the genetic traits and productivity of the cattle population.

m. Is genetic engineering a boon or a bane for the present era? Give your arguments.

Answer 👉 The perception of genetic engineering as a boon or a bane depends on various factors and perspectives. Here are arguments supporting both sides:

Boon:

Medical Advancements: Genetic engineering has enabled the development of life-saving medicines, therapies, and vaccines, including the production of insulin for diabetes treatment and the creation of genetically modified organisms for producing pharmaceutical drugs.
Agricultural Benefits: Genetic engineering has facilitated the development of genetically modified crops with enhanced resistance to pests, diseases, and environmental conditions, leading to increased crop yield and improved food security.
Disease Prevention: Genetic engineering techniques such as gene editing offer the potential to prevent and treat genetic diseases by modifying or correcting faulty genes, opening up possibilities for personalized medicine.
Environmental Conservation: Genetic engineering can be utilized for conservation purposes, such as the preservation of endangered species and the restoration of ecosystems.

Bane:

Ethical Concerns: Genetic engineering raises ethical dilemmas regarding the manipulation of life, including debates about playing god, the potential for unintended consequences, and the unequal distribution of benefits and risks.
Environmental Risks: The release of genetically modified organisms into the environment may have unintended ecological consequences, including the spread of modified genes to wild populations, disruption of ecosystems, and loss of biodiversity.
Unknown Long-Term Effects: Genetic engineering is a relatively new field, and the long-term effects of manipulating genes and ecosystems are still uncertain. There is a need for thorough research, regulation, and risk assessment to address potential unforeseen consequences.
Socioeconomic Implications: Genetic engineering can exacerbate socioeconomic disparities, as access to advanced technologies and genetically modified products may be limited to those with greater resources, leading to potential inequalities in health and agriculture.
Overall, the evaluation of genetic engineering as a boon or a bane depends on careful consideration of its specific applications, ethical implications, potential risks, and long-term consequences.

n. How has Al technology helped to bring happiness to the farmer? Explain.

Answer 👉 AI technology has brought significant happiness to farmers through various ways. Precision farming, enabled by AI-powered tools and sensors, allows farmers to make informed decisions on irrigation, fertilization, and pest control, leading to improved crop yields and reduced resource waste. AI algorithms also help monitor crops, detect diseases early, and optimize irrigation, resulting in better crop health and increased happiness for farmers. Additionally, AI-based crop yield prediction and pest management systems assist farmers in planning and protecting their harvests, leading to improved profitability and a sense of accomplishment.

o. IVFis proved to be a boon for childless couples. Justify this statement.

Answer 👉 IVF has proven to be a remarkable blessing for childless couples. By providing a solution for infertility, IVF allows couples to conceive and have a child. With advancements in techniques and technology, the success rates of IVF have significantly increased, offering hope to couples who desire biological children. IVF also enables the identification and avoidance of genetic disorders through pre-implantation genetic screening, providing peace of mind. Moreover, IVF offers the option of fertility preservation, allowing individuals or couples to freeze embryos, eggs, or sperm for future use, ensuring the possibility of starting a family even after medical treatments.

Unit - 4. वंशानुक्रम

1. तलका प्रश्नको सही विकल्प छनोट गर्नुहोस् ।

(क) मानिसको कोषमा कति जोडा सेक्स क्रोमोजोम हुन्छन् ?

(अ) 1 जोडा

(आ) 22 जोडा

(इ) 23 जोडा

(ई) 46 जोडा

Answer 👉 (इ) 23 जोडा

(ख) क्रोमोजोम के के मिलेर बनेको हुन्छ ?

(अ) DNA र RNA

(आ) DNA र कार्बोहाइड्रेट

(इ) DNA र प्रोटिन

(ई) RNA र प्रोटिन

Answer 👉 (इ) DNA र प्रोटिन

(ग) सेक्स क्रोमोजोमको मुख्य कार्य के हो ?

(अ) सोमाटिक गुण निर्धारण गर्ने

(आ) लिङ्ग निर्धारण गर्ने

(इ) रोग प्रतिरोधक क्षमता बढाउने

(ई) आँखाको बनोट निर्धारण गर्ने

Answer 👉 (आ) लिङ्ग निर्धारण गर्ने

(घ) वंशाणुगत गुण सार्ने क्रोमोजोमको सबैभन्दा सानो एकाइलाई के भनिन्छ ?

(अ) DNA

(आ) क्रोमाटिड

(इ) सेन्टीमियर

(ई) वंशाणु

Answer 👉 (ई) वंशाणु

(ङ) माइटोसिस कोष विभाजनका लागि तलका मध्ये कुन भनाइ ठिक हो ?

(अ) यो कोष विभाजनमा एकै पटकमा चारओटा कोष बन्छन् ।

(आ) यो कोष विभाजनमा हयाप्लोइड कोष बन्छन् ।

(इ) यो कोष विभाजन प्रजनन कोषमा हुन्छ ।

(ई) यो कोष विभाजनले कोषको पुनः निर्माण गर्छ ।

Answer 👉 (ई) यो कोष विभाजनले कोषको पुनः निर्माण गर्छ ।

(च) रेडियोथेरापी ल्यावमा काम गर्ने एक जना टेक्निसियनको विवाहको लामो समयपश्चात् पनि सन्तानको जन्म नहुँदा परीक्षण गराएछन् परीक्षणपश्चात् उनले लामो समयसम्म high intensity radiation मा काम गरेकाले उनमा सन्तान उत्पादन क्षमता कमी भएको देखियो । त्यसमा कोषको कुन भागमा असर परेको होला ?

(अ) DNA

(आ) RNA

(इ) साइटोप्लाज्म

(ई) न्यूक्लियोलस

Answer 👉 (अ) DNA

(छ) यदि कोषमा DNA transcription भएन भने कुन प्रक्रियामा असर पर्छ ।

(अ) प्रकाश संश्लेषण

(आ) प्रोटिन संश्लेषण

(इ) मैथुनिक प्रजनन

(ई) कोष विभाजन

Answer 👉 (आ) प्रोटिन संश्लेषण

(ज) DNA replication हुँदा कुनै एउटा न्यूक्लियोटाइडको नास भयो भने जीवमा के असर पर्छ ?

(अ) जेनेटिक समस्या देखिन्छ ।

(आ) कोष विभाजनमा समस्या आउँछ ।

(इ) प्रजननमा समस्या आउँछ ।

(ई) क्रोमोजोमले काम गर्दैन ।

Answer 👉 (अ) जेनेटिक समस्या देखिन्छ ।

(झ) निम्नमध्ये कुनले महिलाको शरीरमा रहेका कोषको क्रोमोजोमको सङ्केत गर्छ ?

(अ) 44 + XY

(आ) 44 + XX

(इ) 22 + XY

(इ) 22 +XY

Answer 👉 (आ) 44 + XX

(ञ) तलका मध्ये कुन भनाइ सही छ है ।

(अ) अन्डामा Y क्रोमोजोम मात्र हुन्छ भने शुक्राणुमा X क्रोमोजोम हुन्छ ।

(आ) अन्डामा X क्रोमोजोम मात्र हुन्छ भने शुक्राणुमा Y क्रोमोजोम हुन्छ ।

(इ) अन्डामा X क्रोमोजोम मात्र हुन्छ भने शुक्राणुमा X वा Y मध्ये कुनै एक क्रोमोजोम हुन्छ ।

(ई) अन्डा र शुक्राणु दुवैमा X र Y क्रोमोजोम हुन्छन् ।

Answer 👉 (इ) अन्डामा X क्रोमोजोम मात्र हुन्छ भने शुक्राणुमा X वा Y मध्ये कुनै एक क्रोमोजोम हुन्छ ।

2. फरक लेख्नुहोस् :

(क) अटोजोम र सेक्स क्रोमोजोम

अटोजोम

- मानिसको सोमाटिक कोषमा यसको सङ्ख्या 22 जोडा हुन्छ ।

- अटोजोमले शरीरका गुणहरू निर्धारण गर्छ ।

सेक्स क्रोमोजोम

- मानिसको प्रत्येक सोमाटिक कोषमा यसको सङ्ख्या 1 जोडा हुन्छ ।

- सेक्स क्रोमोजोमले लिङ्ग निर्धारण गर्छ ।

(ख) माइटोसिस र मियोसिस

माइटोसिस

- एक समयमा एकचोटी मात्र कोष विभाजन हुन्छ ।

- एक डिप्लोइड कोषबाट दुई डिप्लोइड कोषहरू बन्छन्।

- विभाजनपछि क्रोमोजोमको सङ्ख्या सन्तति कोषमा पनि मातृकोष जत्तिकै हुन्छ ।

मियोसिस

- एक समयमा दुई चोटी कोष विभाजन हुन्छ ।

- एक डिप्लोइड कोषबाट चार हाप्लोइड कोषहरू बन्छन् ।

- विभाजनपछि क्रोमोजोमको सङ्ख्या सन्तति कोषमा मातृकोषको भन्दा आधा हुन्छ ।

(ग) DNA र RNA

DNA

- यो क्रोमोजोममा पाइन्छ ।

- यो एउटा वंशाणुगत पदार्थ हो ।

- DNA को पुरा रुप Deoxyribonucleic Acid हो।

RNA

- यो साइटोप्लाज्समा पाइन्छ ।

- तर यो वंशाणुगत होइन ।

- RNA को पुरा रूप Ribonucleic Acid हो ।

(घ) याप्लोइड र डिप्लोइड

याप्लोइड

- यसले लिङ्ग निर्धारण गर्छ ।

- जोडामा पाईदैन् ।

डिप्लोइड

- यसले शारिरिक गुणहरूको निर्धारण गर्छ ।

- जोडामा पाईन्छ ।

3. कारण दिनुहोस् :

(क) सन्ततितहरूमा बुबा आमा जस्तै गुणहरू हुन्छन् ।

Answer 👉 ः आमा बाबुबाट तिनीहरूका सन्ततिहरूमा क्रोमोजोममा भएका वंशाणुहरूबाट वंशाणुगत गुणहरू प्रसारण गर्ने हुँदा सन्ततिहरूमा बुबा आमा जस्तै गुणहरू हुन्छन् ।

(ख) लिङ्ग निर्धारणमा पुरुषको मुख्य भूमिका हुन्छ ।

Answer 👉 ः पुरुषमा ग्यामेट बन्ने प्रक्रियामा 50% X क्रोमोजोम र 50% Y क्रोमोजोम भएको ग्यामेट बन्छ भने महिलामा एकै किसिमको X क्रोमोजोम भएको ग्यामेट बन्छ । यदि Y क्रोमोजोम भएको भाले ग्यामेट र X क्रोमोजोम भएको पोथी ग्यामेट मिली गर्भाधान भएमा छोरो हुन्छ । त्यसैगरी X क्रोमोजोम भएको भाले ग्यामेट र X क्रोमोजोम भएको पोथी ग्यामेट मिली गर्भाधान भएमा छोरी हुन्छ । पुरुषको ग्यामेटमा x र Y क्रोमोजोम हुने हुँदा 'लिङ्ग' निर्धारणमा पुरुषको मुख्य भूमिका हुन्छ ।

(ग) पुरुषमा x र दुवै खालका सेक्स क्रोमोजोम भए तापनि कसै कसैको छोरीमात्र वा Y छोरामात्र जन्मन्छन् ।

Answer 👉 : कसैको छोरी मात्र जन्मिनुको कारण प्रत्येक चोटी पुरुषको (22 + x) क्रोमोजोम भएको शुक्रकिटको महिलाको (22 + x) क्रोमोजोम भएको अण्ड सँग मिलन भएर हो, त्यसैगरी कसैको छोरामात्र जन्मिनुको कारण प्रत्येक चोटी गर्भाधान हुँदा पुरुषको (22 + Y क्रोमोजोम भएको शुक्रकीट र महिलाको (22 +X) क्रोमोजोम भएको अण्ड सँग मिलन भएर हो ।

(घ) मियोसिस कोष विभाजनलाई रिडक्सन डिभिजन पनि भनिन्छ ।

Answer 👉 ः मियोसिस कोष विभाजनबाट बनेको चार लैङ्गिक कोषहरूमा क्रोमोजोको सङ्ख्या मातृकोष भन्दा आधा हुन्छ । त्यसकारण मियोसिस कोष विभाजनलाई रिडक्सन डिभिजन पनि भनिन्छ ।

(ङ) माइटोसिस कोष विभाजनलाई समीकरणीय विभाजन पनि भनिन्छ ।

Answer 👉 ः माइटोसिस कोष विभाजनबाट बनेका दुईवटा सोमाटिक कोषहरूमा क्रोमोजोमको सङ्ख्या मातृकोषमा जत्तिकै हुन्छ । त्यसकारण माइटोसिस कोष विभाजनलाई समीकरणीय विभाजन पनि भनिन्छ ।

(च) मियोसिस कोष विभाजनबिना मैथुनिक प्रजनन सम्भव छैन ।

Answer 👉 : प्रत्येक वंशको निरन्तरता र एकरूपताका लागि मैथुनिक प्रजनन् हुने जीवहरूमा मियोसिस कोष विभाजन आवश्यक छ । त्यसकारण मियोसिस कोष विभाजनबिना मैथुनिक प्रजनन् सम्भव छैन ।

(छ) मियोसिस कोष विभाजनले परिवृत्ति ल्याउँछ ।

Answer 👉 : मियोसिस कोष विभाजनको दौरानमा हुने रिकम्बिनेसन र स्वन्त्र गुण प्रसारणको नियम अनुसार प्रत्येक ग्यामेटमा DNA को फरक फरक समूह रहेको हुन्छ । जसमा जाइगोट बन्दा वंशाणुहरूको छुट्टै संयोजन हुन्छ जसले परिवृत्ति ल्याउँछ । त्यसकारण मियोसिस कोष विभाजनले परिवृत्ति ल्याउँछ ।

4. तलका प्रश्नको Answer लेख्नुहोस् :

(क) वंशाणु केलाई भनिन्छ ?

Answer 👉 : क्रोमोजोममा भएको एउटा विशेष गुण बोकेका DNA को सबैभन्दा सानो अंशलाई वंशाणु भनिन्छ ।

(ख) क्रोमोजोम केलाई भनिन्छ ? जीवको शरीरमा यसको भूमिका स्पष्ट पार्नुहोस् ।

Answer 👉 : जीव कोषको न्यूक्लियसमा पाइने रिबन जस्ता त्यान्द्रा हरुलाई क्रोमोजोम भनिन्छ | प्रत्येक क्रोमोजोम DNA र प्रोटीन मिलेर बनेको हुन्छ । यसले जीवको शरीरमा जन्तु तथा वनस्पतिको गुण निर्धारण गर्छ । क्रोमोजोमको कार्य आमाबुबा भएको वंशाणुगत गुणलाई सन्ततिमा सार्नु हो ।

(ग) शारीरिक विकासमा माइटोसिस कोष विभाजनको महत्त्व व्याख्या गर्नुहोस् ।

Answer 👉 ः माइटोसिस कोष विभाजनबाट समान आनुवंशिकता भएका कोषको सङ्ख्या वृद्धि हुने हुँदा शारीरिक वृद्धि विकासमा मुख्य भूमिका खेल्छ । यसले शरीरको वृद्धि र खराब तन्तुहरूको मर्मतमा मुख्य भूमिका खेल्दछ ।

(घ) जीवहरूको प्रजननमा मियोसिस र माइटेसिस कोष विभाजनको भूमिका स्पष्ट पार्नुहोस् ।

Answer 👉 ः माइटोसिस कोष विभाजनमा एउटा कोष विभाजन भई उही आकार प्रकार र मातृकोषमा जत्तिकै सङ्ख्यामा क्रोमोजोम भएका दुईवटा कोषहरू बन्दछन् प्रजनन् कोष निर्माण भई तिनीहरूको मिलन भई भ्रुण बन्छ भने उक्त भ्रुणको विकास र वृद्धिमा माइटोसिस कोष विभाजनले सहयोग गर्दछ । मियोसिस कोष विभाजनमा एउटा कोष विभाजित भई मातृकोषमा भन्दा आधा सङख्यामा क्रोमोजोम भएका चारवटा सन्तति कोष बन्छन् । मियोसिस कोष विभाजनबाट हायप्ल्वाइड ग्यामेटहरू बन्दछन् गर्भाधानको समयमा दुइ हायप्ल्वाइड ग्यामेटहरूको मिलन भई आमाबाबुको सोमाटिक कोषमा भए जस्तै डिप्ल्वाइड कोषहरूको निर्माण हुन्छ । यश प्रक्रियाबाट बन्ने कोषहरूमा क्रोमोजोमको सङ्ख्या आधा हुने भएकोले मैथुनिक प्रजनन हुने प्रत्येक जीवको प्रत्येक वंशमा क्रोमोजोमको सङ्ख्या निश्चित भई जीवको अस्थित्व कायम रहन्छ । क्रसिङ्ग ओभर हुने हुँदा क्रोमाटिकको आदान प्रदान भई सन्ततिमा वंशाणुगत भिन्नता आउँछ ।

(ङ) यदि जीवको मातृ प्रजनन् कोषमा मियोसिस कोष विभाजन भएन भने उक्त जीवमा कस्तो असर देखिएला, व्याख्या गर्नुहोस् ।

Answer 👉 ः यदि जीवको मातृ प्रजनन् कोषमा मियोसिस कोष विभाजन भएन भने सन्तति कोषहरूमा क्रोमोजामेको सङ्ख्या स्थिर हुँदैन र प्रत्येक चोटीको मैथुनिक प्रजनन्‌मा क्रोमोजोमको सङख्या डुप्लिकेसन हुन्छ । जसले गर्दा सजीवहरूमा राम्रोसँग प्रजनन् हुँदैन ।

(च) जीवको आनुवंशिक गुणको प्रसारणमा वंशाणुको भूमिका स्पष्ट पार्नुहोस् ।

Answer 👉 ः वंशाणुले जीवको मोर्फोलोजी वा फिनोटाइपलाई नियन्त्रण गर्छ । कोष विभाजनको लागि वंशाणुको प्रतिकृति आवश्यक हुन्छ । वंशाणुहरूले एक पुस्ताबाट अर्को पुस्तामा पैत्रिक गुणहरू सार्ने काम गर्छन् । वंशाणुहरूमध्ये केहीले शरीरका अङ्गहरूको वृद्धि र विकासलाई नियन्त्रण गर्दछन् भने केही बंशाणुहरूले अनुहारको आकार, छाला र कपालको रङ, आँखाको रङ, शरीरको उचाई तथा अन्य गुणहरू नियन्त्रण गर्दछन् । जीवित वस्तुहरूमा आउने भिन्नताहरू पनि वंशाणुको माध्यमद्वारा एक वंशबाट अर्को वंशमा सर्दै जान्छन् ।

(ज) एक महिला गर्भवती छन् उनले छोरी जन्माउन सक्ने सम्भावना कति छ, प्रतिशतमा लेख्नुहोस् ।

Answer 👉 : एक महिला गर्भवती छन् उनले छोरी जन्माउन सक्ने सम्भावना 50% छ ।

(झ) एक जोडी दम्पतीमा तीन जना छोरा मात्र जन्मिए । यसका लागि के पुरुषको अण्डकोषबाट Y क्रोमोजोम भएका शुक्रकीट मात्र उत्पादन भएका होलान् त, स्पष्ट पार्नुहोस् ।

Answer 👉 ः यदि कुनै दम्पतीका तीन जना छोरा मात्र जन्मिए पनि उक्त पुरुषको अण्डकोषबाट X र Y दुवै प्रकारका क्रोमोजोमहरू भएका शुक्रकीट उत्पादन भए तर गर्भधान हुँदा प्रत्येक चोटी पुरुषको (22 + Y) क्रोमोजोम भएको शुक्रकीटसँग महिलाको (22 + X ) क्रोमोजोम भएको डिम्बको मिलन भई गर्भाधान भएको हुनुपर्छ ।

(ञ) क र ख कन्सेप्ट म्याप पूरा गरी यी दुई प्रक्रियाहरु बिच भिन्नता लेख्नुहोस् ।

प्रजनन कोष - कोष विभाजन (मियोसिस) - ग्यामेट

(क) शारीरिक कोष - कोष विभाजन (माइटोसिस) - डिप्लोइड कोषहरू

(ख) माइटोसिस कोष विभाजन र मियोसिस कोष विभाजनबिच हुने फरकहरू

माइटोसिस कोष विभाजन

- माइटोसिस कोष विभाजनमा एउटा डिप्ल्वाइड माउकोषबाट दुईओटा डिप्ल्वाइड सन्तति कोषहरू बन्छन् ।

- यो विभाजन सोमाटिक कोषमा मात्र हुन्छ ।

मियोसिस कोष विभाजन

- मियोसिस कोष विभाजनमा एउटा डिप्ल्वाइड माउकोषबाट चारओटा हायप्ल्वाइड सन्तति कोषहरू बन्छन् ।

- यो विभाजन प्रजनन कोषमा मात्र हुन्छ ।