Question

Tiffany and Joe have just had a baby and are very surprised to learn that their baby is albino with very pale skin and hair color. Tiffany‘s sister has come to see the new baby, so Joe goes out to talk with his sister Vicky. Joe is very angry. He tells Vicky, "I think Tiffany had an affair with Frank! He’s the only albino we know. Obviously, Tiffany and I aren't albino, so Frank must be the father."
1. Luckily, Vicky remembers her high school biology, so she explains, “Two parents with normal skin and hair color can have an albino baby, if they are heterozygous and carry a recessive allele for albinism.” She draws a Punnett Square to show this. Draw the Punnett Square. Use A for the dominant allele that results in normal skin and hair color and a for the recessive allele that can result in very pale skin and hair color.
2. Joe is still mad and he doesn't understand Vicky's explanation. He says "You aren't even speaking English! What does heterozygous mean? What's a recessive allele? And what's the connection between alleles and skin color?" Answer his questions.
3. Joe says "Okay, I'm beginning to understand, but what are zygotes? What's the connection between the zygotes in the Punnett square and our baby?" Answer Joe's questions.

Answer 1

Ans .

Starting with the punnet square

	A	a
A	AA	Aa
a	Aa	aa

25% chance the offspring is albino .

75% chance child is normal for skin colour.

Alleles are alternate forms of genes . Each chromosome carries two alleles for a trait , say the trait here is skin colour . So each Chromosome will carry say an A allele for normal skin colour , and a allele for an albino . Now A allele is dominant and a is recessive . Dominant means it can supress the recessive allele , that is override the wffects of revessive allele . In this case the A allele for normal skin can supress or override the a allele which is for albinism.

A recessive allele can never override or supress the effects of dominant allele . Ao the recessive trait that is albiniam in this case can only he expressed when two aa alleles ovcur in a pair ,

When two recessive allele pair up in gene its homozygous recessive genotype. So aa is homozygous recessive

When two dominant alleles pair up in a gene ,it is homozygous dominant genotype. AA is a pair of dominant alleles so homozygous dominanant.

Heterozygous is a pair of two dissimilar alleles ,that is Aa. In Heterozygous condition since one copy of dominant allele A is present it overrides recessive allele a and the individual will be normal ,but can transmit the albino allele a to their child.

3 a zygote occurs when a sperm and ovum or egg fuses . The zygote then develops into embryo and the fetus. Sperm and egg each carry a pair of alleles . In joe and tiffany's case sperm carried Aa allele and egg alao carried Aa allele pair so when they fuse there is a possibility that the zygote inherited a allele from father and a allele from mother's egg making the zygote albino.

In punnet square , each square represents the possibilities of how alleles can pair up in a zygote . It can be two A alleles each from jow and tiffany or one A allele from one and a from the other or a allele from both giving rise to an albino baby .

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