Exam 4: Inheritance Patterns of Single Genes and Gene Interaction

You discover a new allele of a gene important for tail formation in mice. WT mice have long tails, but mice heterozygous for the allele have short tails. When you cross two heterozygous mice together, you obtain a 2:1 ratio of short- tailed mice to long- tailed mice. None of the short- tailed progeny are homozygous. What type of allele results in short tails?

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?

A certain species of morning glories produces flowers that are blue, red, or purple. Two pure- breeding purple lines are crossed and produce F1 progeny that all make blue flowers. The F1 allowed to self and produce 320 F2 progeny with the following distribution: 185 blue, 115 purple, an red. Which the following is NOT consistent with this information?

The parental cross between a rabbit with the Himalayan phenotype (genotype chch) and an albino rabbit (genotype cc) results in F1 rabbits that all have the Himalayan phenotype (genotype chc). If the resulting F1 rabbits are crossed, what proportion of the F2 offspring will have the Himalayan phenotype and what causes the hypomorphic ch allele to be unstable and result in the distinctive fur pattern?

In certain goat breeds, appearance of a chin beard is a sex- influenced trait. Recall that bearding is inherited as an autosomal trait determined by two alleles, B1 and B2, and females must be homozygous for the bearded allele, B2, to have a beard. What genotypes must a bearded billy goat (male) and a beardless female goat have if they have a bearded female offspring?

In the biosynthetic pathway for conversion from homoserine to methionine, you identify a Neurospora crassa double mutant Met1/Met2. This mutant will grow only if which supplement(s) are added to the minimal media? Growth Medium Mutant strain Minimal medium Minimal+ cysteine Minimal+ cystathionine Minimal+ homocysteine Minimal+ methionine Compound accumulating in mutant Control prototroph + + + + + None Met 1 - - - - + Homocysteine Met 2 - - - + + Cystathionine Met 3 - - + + + Cysteine Met 4 - + + + + Homoserine

You cross a pure- breeding white flower with a pure- breeding red flower, and the offspring are all pink. This is an example of what type of inheritance?

Which of the following is correct regarding individuals who are blood type AB?

Complementation tests of distinct recessive mutants, 1 through 8, produce the data in the matrix below. A plus (+) indicates complementation, meaning the phenotype of the combined alleles is wild type, and a minus (- ) indicates a failure to complement meaning that a mutant phenotype results. Assume that the missing mutant combinations would yield data consistent with the entries that are shown. How many complementation groups are formed by these eight mutants?

A man with blood type A (whose mother was blood type O) has children with a woman that has blood type AB. The man and the woman are also heterozygous for the H antigen. What is the probability that they will have a child with blood type A?

Mendel studied tall and short pure- breeding lines of pea plants. Inherited genetic variation would dictate that one line would produce tall plants and the other short plants, but the genes and phenotypes are influenced by what external factor?

Which mode of inheritance results in both alleles being detected equally in the heterozygous phenotype?

Wild- type bacteria can grow on minimal medium. Four mutants that cannot grow on minimal med but can grow on minimal medium supplemented with the nutrient "H" are isolated. It is suspected t metabolites T, P, and A are in the biochemical pathway for synthesis of H, so each mutant is tested f ability to grow on minimal medium supplemented with these metabolites: A. Mutant 1: can grow on minimal medium supplemented with T, but not P or A B. Mutant 2: is unable to grow on minimal medium supplemented with T, P, or A C. Mutant 3: is able to grow on minimal medium supplemented with A or T, but not P D. Mutant 4: can grow on minimal medium supplemented with T, P, or A. Which of the following is NOT consistent with this information?

Deafness is caused by recessive mutations in any one of at least five genes. Two deaf individuals have nine children, all of whom have normal hearing. Which of the following can you conclude?

What are the two categories of gain- of- function mutations?

Which step is catalyzed by the enzyme responsible for the Met 2 mutant? Growth Medium Mutant strain Minimal medium Minimal+ cysteine Minimal+ cystathionine Minimal+ homocysteine Minimal+ methionine Compound accumulating in mutant Control prototroph + + + + + None Met 1 - - - - + Homocysteine Met 2 - - - + + Cystathionine Met 3 - - + + + Cysteine Met 4 - + + + + Homoserine

Describe the difference between incomplete penetrance and variable expressivity. It is often difficult to pinpoint the cause of incomplete penetrance or variable expressivity. What possible interactions may be responsible?

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__________ .

Which antigen, expressed on the surface of all red blood cells, is modified by A- or B- transferases?

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