Question 1

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?

Accepted Answer

A)   temperature- sensitive allele
B)   lethal allele
C)   incompletely penetrant allele
D)   partially dominant allele
E)   dominant negative allele B

Question 2

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?

Accepted Answer

D is haploinsufficient.

Question 3

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?

Accepted Answer

A)   Blue- flowering plants are either A_bb or aaB_.
B)   The pure- breeding parental parents are homozygous recessive for mutations in two different genes.
C)   Dominant gene interaction appears to result in a 9:6:1 ratio.
D)   Analysis of the F1 and F2 progeny phenotypes suggests epistasis.
E)   Red- flowering plants are homozygous recessive for both genes. A

Question 4

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?

Accepted Answer

A)   3/4; complementation
B)   1/2; complementation
C)   3/4; temperature
D)   1/4; temperature
E)   1/2; temperature

Question 5

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?

Accepted Answer

A)   The bearded billy goat must be heterozygous for the bearded allele, while the beardless female must be homozygous for the bearded allele.
B)   The bearded billy goat could be heterozygous or homozygous for the bearded allele, while the beardless female must be homozygous for the bearded allele.
C)   Both the bearded billy goat and beardless female must be heterozygous for the bearded allele.
D)   The bearded billy goat could be heterozygous or homozygous for the bearded allele, while the beardless female must be heterozygous for the bearded allele.
E)   Both the bearded billy goat and beardless female must be homozygous for the bearded allele.

Question 6

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?
 $\begin{array} { l  } \text { Growth Medium }\
\hline \begin{array} { l  } 
 \text { Mutant }\ \text {strain }\
\end{array}&\begin{array} { l  } 
 \text { Minimal}\ \text { medium}\
\end{array}&\begin{array} { l  } 
 \text { Minimal+}\ \text {cysteine }\
\end{array}&\begin{array} { l  } 
 \text { Minimal+}\ \text {cystathionine }\
\end{array}&\begin{array} { l  } 
 \text {Minimal+ }\ \text {homocysteine }\
\end{array}&\begin{array} { l  } 
 \text { Minimal+}\ \text { methionine}\
\end{array}&\begin{array} { l  } 
 \text { Compound}\ \text {  accumulating}\ \text {  in mutant}\
\end{array}\
\hline
\begin{array} { l  } 
 \text { Control}\ \text {prototroph }\
\end{array}&+&+&+&+&+& \text {None }\
\text { Met } 1&-&-&-&-&+&\text { Homocysteine }\
\text { Met } 2&-&-&-&+&+&\text { Cystathionine }\
\text { Met } 3&-&-&+&+&+&\text { Cysteine }\
\text { Met } 4&-&+&+&+&+&\text { Homoserine }\
\end{array}$

Accepted Answer

A)   cystathionine and homocysteine
B)   homocysteine only
C)   cysteine only
D)   methionine only
E)   homoserine only

Question 7

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?

Accepted Answer

The answer of You cross a pure- breeding white flower...

Question 8

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

Accepted Answer

A)   Their blood cells clump when they receive blood from an individual with the genotype IAi.
B)   They express B- transferase that adds N- acetylgalactosamine to the H antigen.
C)   They do not carry the A or B antigen.
D)   They are the universal recipients.
E)   They carry both the anti- A and anti- B antibodies.

Question 9

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?

Accepted Answer

A)   4
B)   5
C)   6
D)   2
E)   3

Question 10

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?

Accepted Answer

A)   0
B)   1/8
C)   3/4
D)   1/2
E)   3/8

Question 11

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?

Accepted Answer

The answer of Mendel studied tall and short pure- breeding...

Question 12

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

Accepted Answer

A)   complete dominance
B)   incomplete dominance
C)   codominance
D)   epistasis
E)   incomplete penetrance

Question 13

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?

Accepted Answer

A)   Mutant 3 blocks the conversion of metabolite P  →metabolite A
B)   Mutant 4 blocks a step before all the metabolites
C)   Mutant 1 will cause a build up of metabolite A
D)   Mutant 1 blocks the conversion of metabolite T -metabolite H
E)   Mutant 2 blocks a step right before metabolite H

Question 14

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?

Accepted Answer

A)   The mutations are codominant to the normal allele.
B)   The parents have the same mutated protein involved in inner ear development.
C)   The parents have mutations in different genes.
D)   The mutations are incompletely dominant to the normal allele.
E)   The parents have mutations in the same gene.

Question 15

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

Accepted Answer

The answer of What are the two categories of gain-...

Question 16

Which step is catalyzed by the enzyme responsible for the Met 2 mutant? $\begin{array} { l  } \text { Growth Medium }\
\hline \begin{array} { l  } 
 \text { Mutant }\ \text {strain }\
\end{array}&\begin{array} { l  } 
 \text { Minimal}\ \text { medium}\
\end{array}&\begin{array} { l  } 
 \text { Minimal+}\ \text {cysteine }\
\end{array}&\begin{array} { l  } 
 \text { Minimal+}\ \text {cystathionine }\
\end{array}&\begin{array} { l  } 
 \text {Minimal+ }\ \text {homocysteine }\
\end{array}&\begin{array} { l  } 
 \text { Minimal+}\ \text { methionine}\
\end{array}&\begin{array} { l  } 
 \text { Compound}\ \text {  accumulating}\ \text {  in mutant}\
\end{array}\
\hline
\begin{array} { l  } 
 \text { Control}\ \text {prototroph }\
\end{array}&+&+&+&+&+& \text {None }\
\text { Met } 1&-&-&-&-&+&\text { Homocysteine }\
\text { Met } 2&-&-&-&+&+&\text { Cystathionine }\
\text { Met } 3&-&-&+&+&+&\text { Cysteine }\
\text { Met } 4&-&+&+&+&+&\text { Homoserine }\
\end{array}$

Accepted Answer

A)   homocysteine  ?methionine
B)   methionine  ?homoserine
C)   homoserine  ?cysteine
D)   cysteine ?cystathionine
E)   cystathionine  ?homocysteine

Question 17

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?

Accepted Answer

The answer of Describe the difference between incomplete penetrance and...

Question 18

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__________ .

Accepted Answer

A)   null/ amorphic
B)   hypomorphic
C)   hypermorphic
D)   neomorphic
E)   dominant negative

Question 19

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

Accepted Answer

The answer of Which antigen, expressed on the surface of...

Question 20

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

Accepted Answer

The answer of If an organism with a particular genotype...

Exam 4: Inheritance Patterns of Single Genes and Gene Interaction