Question

Name: Select from the terms below to answer questions #13-16. One term is not used. M) Lethal mutation N) Loss-of-function mutation O) Gain-of-function mutation P) Conditional mutation Q) Wild-type allele 13) Manx (tailless) cats are heterozygous for the T allele; cats with normal tails are tt. If you mate a Manx to a Manx, 1/3 of the kittens have tails. The reason that there no purebred Manx cats is because this phenotype is caused by a 14) in humans, albinism is the result of a mutation in a pathway that converts the amino acid tyrosine to the skin pigment melanin. The general term for this type of mutation is 15) In Himalayan rabbits, the ears, feet, and muzzle are pigmented while the rest of the body is white. This is because they express an enzyme variant that is le at warm body temperatures but functions at the lower temperatures experienced by cells of the extremities. This is an example of a 16) Thomas Hunt Morgan noticed that the majority of Drosophila have red eyes, but he also discovered some white-eyed flies. Morgan termed the form of a gene that is most common in a population as a Select from the terms below to answer questions #17-22. One term is not used. R) Genomic imprinting S) Methylation T) Sex-influenced inheritance U) Maternal inheritance V) Sex-limited inheritance W) Complementation X) X-linked inheritance 17) Pattern baldness is controlled by two alleles: B, b. Females are bald if they are hom e (RR bus malesonly need on allele B to be bold Tbie treit jean

Answer 1

13) Manx (tailless) cats are heterozygous for the T allele; Cats with normal tails are tt. If you mate a Manx to Manx, 1/3 kittens have tails. The reason that there wer no purebred Manx cats is because this phenotype is caused by ‘lethal mutation’

The Manx gene for tailllessness is very penetrant and dominant in nature. When two Manx parents mate, kitten are usually born without a tail. A homozygous condition for this gene results in lethality and miscarriage for the cat. Thus, tailless cats can possess only one copy of the allele t.

14) In humans, albinism is the result of a mutation in a pathway that converts the amino acid tyrosine to the skin pigment melanin. The general term for this type of mutation is ‘loss-of-function mutation’.

Albinism is caused due to a congenital defect in production of pigment melanin due to an autosomal recessive defect in enzyme.

15) In Himalayan rabbits, the ears, feet, and muzzle are pigmented while the rest of the body is white. This is because they express an enzyme variant that is ineffective at warm body temperatures but functions at the lower temperatures experience by the extremities. This is an example of a ‘conditional mutation’.

Here the conditional mutation refers to a state where wild type phenotype is expressed under “permissive” environment (high temperature) and a mutant phenotype is expressed under restrictive conditions (Low temperature).

16) Thomas Hunt Morgan noticed that the majority of Drosophila have red eyes, but he also discovered some white eyed flies. Morgan termed the form of a gene that is most common in population as a ‘wild type allele’

The allele that encodes a phenotype which is frequent and most commonly observed in nature is known as a wild type allele.