(a) Offspring have the same characteristics as their parents.

→ Because, in the process of cell division the both characteristics from the parents were transmitted to their offspring.

(b) The male have a main role in the determination of sex.

→ Because, female only have XX chromosomes, but male have both X and Y chromosomes. Therefore, the sex chromosome that a male sperm carries determines whether the offspring will be male or female.

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

→ Because, to determines sex, both male and female gamets are equally necessary. If the X and X chromosome of male and female fused, the zygote will be son or daughter. It is a 50/50 chance.

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

→ Because, in the process of cell division number of chromosomes in daughter cell is reduced to half than that of parent cell.

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

→ Because, in the process of cell division the chromosome number in each daughter cell is equal to that in the parent cell.

(f) Sexual reproduction is impossible without meiotic cell division.

→ Because, this cell division forms male and female gamets that are necessary for sexual reproduction.

(g) Meiotic cell division brings variation.

→ Meiotic cell division brings variation because of recombination and independent assortments.

(a) What is a gene?

→ A gene is a smallest fragment of DNA in a chromosome which codes or represents a specific character of an organism.

(b) What is chromosomes? Clarify the role of chromosomes in the body of living beings.

→ The fibers which become short, thickened and also prominent during cell division is called chromosomes. The role of chromosomes in the body of living beings is to carry the genetic information of an organism that determine various traits and characteristics of an organism.

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

→ The importance of mitotic cell division is that it allows for the growth and development of an organism by increasing the number of cells through repeated rounds of mitosis; cell divide and multiply, leading to the development of tissues and organism.

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

The role of mitosis and meiosis in the reproduction of organism are:

Mitosis:

• It involves in asexual reproduction.
• During this, single cell divides into genetically identical daughter cell.

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

→ If meiotic cell division does not occur in the reproductive cell of an organism several consequences would arise. They are:

• Failure to produce haploid gamets.
• Lack of genetic diversity.
• Difficulty in sexual reproduction.
• Increased chromosome number.

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

→ The role of genes in the transmission of hereditary characteristics are:

• Offsprings inherit genes from their parents which make them alike.
• It creates variations in traits among individual.
• Through it mutation and evolution take place in other generations.
• It carries the instructions for the synthesis of specific proteins or RNA molecules.

(g) How sex is determined in human. Explain with chart.

(h) A women is pregnant, what is her probability of giving birth to a daughter? Write in percent.

→ The probability of giving birth to a daughter is 50%.

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

→ No, the testes produce both X and Y chromosome carrying by sperm. Having only a son is just a matter of chance.

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

→ Because, some character were transmitted to offspring during cell division which may look alike but not exactly the same.

(b) Mendel selected pea plants for his experiment.

→ Because, pea plants are easily available, affordable, fast growing, having pair of contrasting characters and easy to cultivate.

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

→ Because, tall character is dominant and dwarf is a recessive character in F1 generation. Dominant character is expressed externally in F1 generation.

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

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

→ Because, DNA is unique, and it can match evidences like hair, blood from the crime scene.

(f) Genetic engineering involves the detailed study of DNA.

→ Because, it is complex and highly sensitive task in which simple error can lead to significant inaccuracies, so it need a detail study.

(g) Offspring produced by cross-breeding may be sterile.

→ Because they are the product from two different species whose chromosomes do not match properly, so they cannot produce gamets for reproduction.

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

→ Because, they can easily get contaminated and lead to inaccuracies during testing of DNA.

(a) What is genetics?

→ The branch of biology that deals with the study of genes, heredity and variation is called genetics.

(b) What is DNA testing? For what purpose it is used?

→ The scientific method which is used to check the structure of DNA and clues is called DNA testing. It is generally used for the investigation of various criminal cases.

(c) Give some examples of genetics technology.

→ Some examples of genetics technology are:

• Genetic engineering.
• Polymerase chain reaction.
• Gene therapy.
• DNA sequencing.

(d) Mention the importance of DNA in genetic technology.

(e) Explain the importance of genetic engineering.

→ Following are the importance of genetic engineering:

• Identifying genes and their functions.
• To change and regulate plant characteristics.
• Agricultural production.

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

→ The cross made between two pure plants or organisms considering a pair of contrasting characters is called mono hybrid cross.

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

→ When pure black and pure white rats are crossed, then we will get hybrid black in F1 generation and when they again get crossed one is pure black, two are hybrid and one is pure white which shows that Mendel’s experiment can be done in animals as well.

Here, pure black = BB
Pure white = bb.

(h) Explain the Mendel’s law of dominance and purity of gamets.

→ According to Mendel’s law of dominance when a cross is made between two pure individuals having a pair of contrasting characters, only one character is expressed externally in F1 generation, which is called the dominant character.

According to Mendel’s law of purity of gamets, in the formation of gamets, in the hybrid, during meiosis cell division, the genes of the pure or hybrid alleles in the mother cell are separated and only pure characters enter each gamets.

(i) Round seeded pea plants and wrinkled seeded pea plant are cross-pollinated first and then the offspring obtained were self-pollinated again. The result of the second filial generations is shown in the table below. Now answer the questions.

(i) What is the ratio of plants showing dominant and recessive characters?

→ Dominant: 3
Recessive: 1
3 : 1

(ii) Write genotypic and phenotypic ratio of this generation.

→ Phenotypic ratio: 3 : 1
Genotypic ratio: 1 : 2 : 1

(iii) Among them which plant is purely round-seeded? Why?

→ Among them RR is purely round-seeded seed. Because it shows the dominant character of parents.

(iv) 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 pig did not appear in this generation.

→ All black guinea pigs were shown in (F1) generation because, black guinea pig have dominant character, which follows the law of dominance and white guinea pig did not appear in this generation.

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

→ The father of that child can be detected by DNA testing of that baby with the suspected people.

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

→ Artificial Insemination (AI) technology were used in this condition, which is the technique of collecting semen from advanced breeds of male and allowing them to enter the female reproductive tract at the right time through the use of equipment.

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

→ In my opinion, genetic engineering is a boon for the present era because this technology helps to develop new qualities by making various change in DNA easily and quickly. By this technology, modification in the genetic material or gene is carried out and also scientists have been able to find out what genes are, their function and how they can be altered by adding, deleting and substituting DNA.

(n) How has AI technology helped to bring happiness to the farmer? Explain.

→ AI technology helped farmers because there is no rearing male for breeding, which save expenses, it help to control the infection and spread of disease during mating, it even increases the rate of fertilization.

(o) IVF is proved to be a boon for childless couples. Justify this statement.

→ Because it allow conception by using a couple’s own sperm and ovum or by the use of donor’s sperm and ovum. It have high chances of success and it is the best method for conception.