MUST SHOW ALL WORK FOR ALL OF THE FOLLOWING QUESTIONS AND BE VERY DETAILED AND S

Question

MUST SHOW ALL WORK FOR ALL OF THE FOLLOWING QUESTIONS AND BE VERY DETAILED AND SPECIFIC. ALSO MUST SHOW ANY SORT OF DIAGRAM OF HOW THE ANSWER WAS FOUND AND EXPLAIN IT COMPLETELY:

1. Color blindness is a sex-linked recessive trait. A man and his wife who both have normal vision have a female child who is color blind and has Turner Syndrome (XO). Diagram this cross including the gametes that produced this child.

2. In humans, normal skin pigmentation is influenced by a dominant gene (C), which allows pigmentation to develop. All individuals who are homozygous for the recessive allele (c) are unable to produce an enzyme needed for melanin formation and are therefore referred to as albino. Two normal parents produce an albino child. What are the chances the next child will be an albino?

3. Chickens with shortened wings and legs are called "creepers." When creepers are mated to normal birds they produce creepers and normals with equal frequency. When creepers are mated to creepers they produce 2 creepers to 1 normal. Crosses between normal birds produce only normal progeny. How can these results be explained?

Explanation / Answer

1. Turner syndrome occurs when one X chromosome is missing. Here the offspring is a female child so her genotype is XO. The reason for missing X chromosome could be "Non-Disjunction" of chromosomes during meiosis. This means distribution of chromosomes is not equal and proper to the daughter cells, resulting in one cell being XO.

Now talking of color blindness, its a X-linked disorder. Since daughter has it, it means mother is the carrier. Father can't be because he is not color blind.

Mother = XXc and Father = XY.

Possible outcomes of offsprings can be-

Here since we need affected daughter and that too with Turner syndrome. Then the first outcome "XXc" suits the condition. The dominant X chromosome might have lost during non-disjunction and since only recessive allele [for colorblindness] is left. The girl is both color blind and has Turner syndrome.

2. Normal parents have albino child. that means both are carriers.

Father / Mother = Cc

Possible outcomes would be-

Here chances of being an "Albino" child is 25% or 1/4th. Therefore, chances of next child will also be same i.e. 25%. This is because the events of child birth is an independant event.

3. This is a case of Lethal alleles.

Here the normal bird genotype is CC and that of creepers is "Cc" i,e, heterozygous. In this case, recessive homozygous "cc" is lethal genotype.

Case 1- Normal * Creepers CC * Cc

Outcome CC or Cc [equal number]

Case 2- Normal * Normal CC * CC

Outcome All CC [normal]

Case 3- Creepers * Creepers Cc * Cc

Outcomes 1 CC : 2 Cc : 1 cc

But here cc is lethal so the ratio left is = 1 CC [normal] : 2 Cc [creepers].

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