Question 1

Question 3Outline a project which aims to find the dominant coat colour in dogs.

Accepted Answer

Following are the steps that should be followed in order to find the dominant coat colour in dogs:Find the homozygous male for coat colour.Find the homozygous female for contrasting coat colour.Both are mated to get F1 generation.The colour of coat of progeny will be the dominant colour.

Question 2

Question 1How do Mendel's experiments show that traits may be dominant or recessive?

Accepted Answer

Mendel used a number of contrasting visible characters of garden peas – round/wrinkled seeds, tall/short plants, white/violet flowers and so on. When he crossed plants with contrasting characters, there were no halfway characteristics in the first generation. For example, if a tall plant was crossed with a short plant, all plants were either tall or short and no plant was found with medium height. In F2 generation cross between two tall plants gave short plant as well. This proved that there are two contrasting characters out of which one is dominant which masks the effect of other which is recessive.

Question 3

Question 2How do Mendel's experiments show that traits are inherited independently?

Accepted Answer

Mendel crossed a tall pea plant with round seeds with a short pea plant with wrinkled seeds. The F1 progeny were all tall with round seeds. Thus, tallness and round seeds are the dominant traits.Mendel then used F1 progeny to generate F2 progeny by self-pollination. He observed that some F2 progeny were tall plants with round seeds, and some were short plants with wrinkled seeds. However, he also found that some F2 progeny showed new combinations like tall but with wrinkled seeds, while others would be short but have round seeds. Thus, Mendel’s experiments showed that traits are inherited independently.

Question 4

Question 4How is the sex of the child determined in human beings?

Accepted Answer

In humans, the males have 'XY' chromosomes and females have 'XX' chromosome as sex chromosomes. Therefore, 50% male gametes have X chromosome and other 50% have Y chromosome. The females have all gametes with X chromosome. The sex of the child is determined at the time of fertilisation. If male gamete with X chromosome fertilizes with female gamete, it leads to a female child whereas if a gamete with Y chromosome fertilizes with female gamete, it leads to a male child.

Heredity

Exercises

Intext Questions 2