Exam 4: Gene Interaction

Explain how the cʰ (Himalayan)allele and tyrosinase control the Siamese coat-color pattern.What is the underlying reason that certain parts of a Siamese cat (e.g.,tail and ears)are darker than the cat's trunk?

Phenylketonuria (PKU)is caused by the absence of the enzyme phenylalanine hydroxylase,which catalyzes the first step of the pathway that breaks down the amino acid phenylalanine,a common component of dietary protein.Explain how environmental intervention is commonly practiced to prevent the development of this human autosomal recessive condition.

Iᴬ and Iᴮ alleles exhibit ________ over the i allele.

Two proteins interact to form a multimeric complex.When one of the proteins is mutated,there is a substantial loss of functional activity in the multimeric protein.This type of mutation is classified as

Most people with the dominant mutant polydactyly allele have extra digits,but at least 25% have the normal number of digits.What is the genetic explanation for this observation?

________ mutations decrease or eliminate gene activity.

A metabolic reaction requires 10 units of enzymatic activity to proceed.If a dominant allele "D" can generate 8 units of enzyme and a recessive allele "d" can generate 2 units of enzyme,what can be said of the dominant wild-type allele?

________ mutations cause overexpression or result in new functions.

Refer to the the table to answer the following questions. -Which step is catalyzed by the enzyme responsible for the Met 3 mutant?

Which type of pathway is responsible for melanin productionthe biosynthetic pathway,signal transduction pathway,or developmental pathway?

The allele responsible for the Siamese coat-color pattern produces an unstable tyrosinase enzyme.This type of gene product is an example of what type of allele?

What type of allele is often detected as a distortion in segregation ratios,where one class of expected progeny is missing?

Proper cross-matching of blood type is essential for safe blood transfusion.What is the general rule for safe blood transfusion,and what are the consequences if a patient receives the incorrect blood type by accident? If a patient's blood type is unknown,what is the safest course of action?

A mutation results in a gene product with a novel function that is not normally found in wild-type organisms.This type of mutation is known as

A mutation results in an enzyme that is partially active compared to the wild-type allele.This type of "leaky" mutation is classified as

In Labrador retrievers,coat color is controlled by gene interaction in which homozygosity for a recessive allele can mask the phenotypic expression of a second gene.This genetic interaction is known as ________ and has a characteristic ________ ratio.

What are the three categories of loss-of-function mutations?

Many oncogenes result from mutations that cause a protein to be expressed in cells where it is normally not expressed or at inappropriate times during development.This type of mutation can be described as

Which mode of inheritance produces heterozygotes with phenotypes that differ from either homozygote but more closely resembles one homozygous phenotype than the other?

If an organism with a particular genotype fails to produce the corresponding phenotype,the organism is said to be ________ for the trait.