Question

1. A gene can have many alleles. Why is it that any given person only carries two copies of each allele? Pick one below

		This is a function of co-dominance, or incomplete dominance.
		During fertilization a gamete only contributes one allele from each parent.
		Chromosomes lose the extra alleles during cross over or recombination.
		Having more than one allele results in cell death.

2. The X-linked recessive trait of color-blindness is present in 5% of males. If a mother who is a carrier and father who is unaffected plan to have 2 children, what is the probability the children will both be male and color-blind?
Please enter a percentage number with up to three decimals

Answer 1

Answer-

During fertilization a gamete only contributes one allele from each parent.

For a given trait , the male and female gamete each carry one allele which on fertilisation fuse to form a zygote which contains both the Alleles one from each parent .

2- 6.25%

So there is 50% chance one of the male offsprings will be colorblind and 50% chance female offspring will be a carrier.

Totally a 25% chance that one of the child will be a color blind male.

Now mother has two different alleles a color vision recessive allele and normal allele for dominant normal vision so there is 50% chance one of the sons will receive it and as whole 25% chance among all possibilities that one of the male offsprings will receive the color blindness allele. So if two sons are to receive the color blindness allele it is a 25% chance . Also there is a 50% chance one of all offsprings will be a male ,so to have two males

= 5 X 5 = 25 %.

Now there is 25% chance of having two sons and also 25% (1/4) chance that they both will be color blind , so

1/4 x 1/4 = 1/16 which in decimal points is 6.25%.

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