Question 1

You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), bS1U1P1rS1S1P0 (red), bS1U1P1gS1S1P0 (green), and bS1U1P1yS1S1P0 (yellow). B is dominant to all the other alleles, and bS1U1P1y S1S1P0is recessive to all the other alleles. The bS1U1P1gS1S1P0 allele is dominant to bS1U1P1yS1S1P0 but recessive to bS1U1P1rS1S1P0. You cross a pure-breeding brown spider with a pure-breeding green spider. -Predict the genotype of the progeny. A) B/b^g B) B^r/b^g C) b^r/b^y D) b^y/b^g E) B/b^y

Accepted Answer

The correct answer is A because the brown spider is homozygous dominant (BB) and the green spider is homozygous recessive (bS1U1P1gS1S1P0bS1U1P1gS1S1P0). The progeny will all be heterozygous (BbS1U1P1gS1S1P0).

Question 2

You are studying body color in an African spider and have found that it is controlled by a single gene with four alleles: B (brown), bS1U1P1rS1S1P0 (red), bS1U1P1gS1S1P0 (green), and bS1U1P1yS1S1P0 (yellow). B is dominant to all the other alleles, and bS1U1P1y S1S1P0is recessive to all the other alleles. The bS1U1P1gS1S1P0 allele is dominant to bS1U1P1yS1S1P0 but recessive to bS1U1P1rS1S1P0. You cross a pure-breeding brown spider with a pure-breeding green spider. 
-Predict the phenotype of the progeny.
A) half brown, half green
B) three-fourths brown, one-fourth green
C) all brown
D) all green
E) all yellow

Accepted Answer

The progeny will all be brown because the brown allele (B) is dominant over the green allele (bS1U1P1gS1S1P0).

Question 3

Interactions among the human ABO blood group alleles involve _____ and _____.
A) codominance; complete dominance
B) codominance; incomplete dominance
C) complete dominance; incomplete dominance
D) epistasis; complementation
E) continuous variation; environmental variation

Accepted Answer

The ABO blood group alleles exhibit codominance, as both A and B alleles are expressed when present together, and complete dominance, as the O allele is recessive to both A and B alleles.

Question 4

Suppose that extra fingers and toes are caused by a recessive trait, but it appears in only 60% of homozygous recessive individuals. Two heterozygotes conceive a child. What is the probability that this child will have extra fingers and toes?
A) 0.05
B) 0.10
C) 0.15
D) 0.25
E) 0.33

Accepted Answer

The probability of the child being homozygous recessive is 0.25 (from a Punnett square). Given that only 60% of homozygous recessive individuals express the trait, the probability is 0.25 * 0.60 = 0.15.

Question 5

In the endangered African watchamakallit, the offspring of a true-breeding black parent and a true-breeding white parent are all gray. When the gray offspring are crossed among themselves, their offspring occur in a ratio of 1 black : 2 gray : 1 white. Upon close examination of the coats, each hair of a gray animal is gray. What is the mode of inheritance?
A) one gene pair with black dominant to white
B) one gene pair with codominance
C) one gene pair with incomplete dominance
D) two gene pairs with recessive epistasis
E) two gene pairs with duplicate genes

Accepted Answer

The 1:2:1 ratio and the intermediate gray phenotype suggest incomplete dominance, where neither allele is completely dominant, resulting in a blend of traits in the heterozygote.

Question 6

A mother with blood type B has a child with blood type O. Give all possible blood types for the father of this child.
A) O
B) B, AB
C) A, AB
D) A, B, O
E) A, B, AB, O

Accepted Answer

The child with blood type O must inherit an O allele from both parents. The mother with blood type B can have genotype BO or BB, but since the child is type O, the mother must be BO. Therefore, the father must have at least one O allele, so his blood type could be A (AO), B (BO), or O (OO).

Question 7

In rabbits, an allelic series helps to determine coat color: C (full color), cS1U1P1chS1S1P0 (chinchilla; gray color), cS1U1P1hS1S1P0 (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cS1U1P1chS1S1P0 is dominant to cS1U1P1hS1S1P0 and c, cS1U1P1hS1S1P0 is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cS1U1P1ch S1S1P0> cS1U1P1h S1S1P0> c. -Indicate the phenotypic ratios expected of rabbits with the cross Cc × c^hc. A) 1 full color : 1 chinchilla B) 1 full color : 1 Himalayan C) 1 chinchilla : 1 Himalayan D) 3 full color : 1 chinchilla E) 2 full color : 1 Himalayan : 1 albino

Accepted Answer

The answer of In rabbits, an allelic series helps to...

Question 8

Achondroplasia is a common cause of dwarfism in humans. All individuals with achondroplasia are thought to be heterozygous at the locus that controls this trait. When two individuals with achondroplasia mate, the offspring occur in a ratio of 2 achondroplasia : 1 normal. What is the MOST likely explanation for these observations?
A) Achondroplasia is incompletely dominant to the normal condition.
B) Achondroplasia is codominant to the normal condition.
C) The allele that causes achondroplasia is a dominant lethal allele.
D) The allele that causes achondroplasia is a recessive lethal allele.
E) The allele that causes achondroplasia is a late-onset lethal allele.

Accepted Answer

The allele that causes achondroplasia is a recessive lethal allele. This means that individuals who are homozygous for the allele will die before birth. Therefore, the only offspring that can be produced by two individuals with achondroplasia are heterozygous, which have achondroplasia.

Question 9

In rabbits, an allelic series helps to determine coat color: C (full color), cS1U1P1chS1S1P0 (chinchilla; gray color), cS1U1P1hS1S1P0 (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cS1U1P1chS1S1P0 is dominant to cS1U1P1hS1S1P0 and c, cS1U1P1hS1S1P0 is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cS1U1P1ch S1S1P0> cS1U1P1h S1S1P0> c. -Indicate the phenotypic ratios expected of rabbits with the cross Cc^h × c^hc. A) 1 full color : 1 chinchilla B) 1 full color : 1 Himalayan C) 1 chinchilla : 1 Himalayan D) 3 full color : 1 chinchilla E) 2 full color : 1 Himalayan : 1 albino

Accepted Answer

The cross Cc^h × c^hc results in offspring with genotypes: Cc^h, Cc, c^hc^h, and c^hc. The phenotypes are 1 full color (Cc^h and Cc) and 1 Himalayan (c^hc^h and c^hc).

Question 10

Crossing two yellow mice results in 2/3 yellow offspring and 1/3 nonyellow offspring. What percentage of offspring would you expect to be nonyellow if you crossed two nonyellow mice?
A) 25%
B) 33%
C) 66%
D) 75%
E) 100%

Accepted Answer

Crossing two nonyellow mice, which are homozygous recessive, would result in 100% nonyellow offspring.

Question 11

Polydactyly is the condition of having extra fingers or toes. Some polydactylous persons possess extra fingers or toes that are fully functional, whereas others possess only a small tag of extra skin. This is an example of:
A) variable expressivity.
B) complete dominance.
C) independent assortment.
D) complementation.
E) cytoplasmic inheritance.

Accepted Answer

Variable expressivity is the phenomenon in which a single genotype can produce a range of phenotypes. In the case of polydactyly, some individuals with the same genotype may have fully functional extra fingers or toes, while others may have only a small tag of extra skin.

Question 12

The R locus determines flower color in a new plant species. Plants that are genotype RR have red flowers, and plants that are rr have white flowers. However, Rr plants have pink flowers. What type of inheritance does this demonstrate for flower color in these plants?
A) complete dominance
B) incomplete dominance
C) codominance
D) complementation
E) lethal alleles

Accepted Answer

This demonstrates incomplete dominance, where the heterozygous genotype (Rr) results in a phenotype (pink flowers) that is intermediate between the two homozygous phenotypes (red and white flowers).

Question 13

A mother with blood type AB has a child with blood type B. Give all possible blood types for the father of this child.
A) O
B) B, AB
C) A, AB
D) A, B, O
E) A, B, AB, O

Accepted Answer

The answer of A mother with blood type AB has...

Question 14

In rabbits, an allelic series helps to determine coat color: C (full color), cS1U1P1chS1S1P0 (chinchilla; gray color), cS1U1P1hS1S1P0 (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cS1U1P1chS1S1P0 is dominant to cS1U1P1hS1S1P0 and c, cS1U1P1hS1S1P0 is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cS1U1P1ch S1S1P0> cS1U1P1h S1S1P0> c. -Indicate the phenotypic ratios expected of rabbits with the cross Cc^ch × Cc^h. A) 1 full color : 1 chinchilla B) 1 full color : 1 Himalayan C) 1 chinchilla : 1 Himalayan D) 3 full color : 1 chinchilla E) 2 full color : 1 Himalayan : 1 albino

Accepted Answer

The cross Cc^ch × Cc^h results in the following genotypes: CC, Cc^ch, Cc^h, Cc, c^chc^h, c^chc, c^hc. The phenotypes are 3 full color (CC, Cc^ch, Cc^h) and 1 chinchilla (c^chc^h).

Question 15

A mother with blood type A has a child with blood type A. Give all possible blood types for the father of this child.
A) O
B) B, AB
C) A, AB
D) A, B, O
E) A, B, AB, O

Accepted Answer

The child has blood type A, which means they could have inherited an A allele from the mother and either an A or O allele from the father. Therefore, the father could have blood type A, B, AB, or O.

Question 16

In rabbits, an allelic series helps to determine coat color: C (full color), cS1U1P1chS1S1P0 (chinchilla; gray color), cS1U1P1hS1S1P0 (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cS1U1P1chS1S1P0 is dominant to cS1U1P1hS1S1P0 and c, cS1U1P1hS1S1P0 is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cS1U1P1ch S1S1P0> cS1U1P1h S1S1P0> c. - Indicate the phenotypic ratios expected of rabbits with the cross Cc^h × cc. A) 1 full color : 1 chinchilla B) 1 full color : 1 Himalayan C) 1 chinchilla : 1 Himalayan D) 3 full color : 1 chinchilla E) 2 full color :1 Himalayan : 1 albino

Accepted Answer

The cross Cc^h × cc results in offspring with genotypes Cc and c^hc. The Cc genotype will express the full color phenotype, and the c^hc genotype will express the Himalayan phenotype. Thus, the phenotypic ratio is 1 full color : 1 Himalayan.

Question 17

In humans, blood types A and B are codominant to each other and each is dominant to O. What blood types are possible among the offspring of a couple of blood types AB and A?
A) A, B, AB, and O
B) A, B, and AB only
C) A and B only
D) A, B, and O only
E) A and AB only

Accepted Answer

The AB parent can pass on either an A or B allele, while the A parent can pass on either an A or O allele. The possible combinations are AA, AO, AB, and BO, resulting in blood types A, B, and AB.

Question 18

A mother of blood type A gives birth to a child with blood type O. Which of the following could NOT be the blood type of the father?
A) A
B) B
C) O
D) AB
E) Any of these is a possible blood type of the father.

Accepted Answer

A child with blood type O must inherit an O allele from each parent. A mother with blood type A can have genotype AO, so the father must have at least one O allele. A father with blood type AB cannot have an O allele, so he cannot be the father.

Question 19

A mother with blood type A has a child with blood type AB. Give all possible blood types for the father of this child.
A) O
B) B, AB
C) A, AB
D) A, B, O
E) A, B, AB, O

Accepted Answer

The child has blood type AB, which means they inherited an A allele from the mother and a B allele from the father. Therefore, the father must have a B allele, so his blood type could be B or AB.

Question 20

In rabbits, an allelic series helps to determine coat color: C (full color), cS1U1P1chS1S1P0 (chinchilla; gray color), cS1U1P1hS1S1P0 (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cS1U1P1chS1S1P0 is dominant to cS1U1P1hS1S1P0 and c, cS1U1P1hS1S1P0 is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cS1U1P1ch S1S1P0> cS1U1P1h S1S1P0> c. - Indicate the phenotypic ratios expected of rabbits with the cross c^chc^h × c^hc. A) 1 full color : 1 chinchilla B) 1 full color : 1 Himalayan C) 1 chinchilla : 1 Himalayan D) 3 full color : 1 chinchilla E) 2 full color : 1 Himalayan : 1 albino

Accepted Answer

The cross c^chc^h × c^hc results in offspring with genotypes c^chc^h, c^chc, c^hc^h, and c^hc. The phenotypes are 1 chinchilla (c^chc^h), 1 chinchilla (c^chc), 1 Himalayan (c^hc^h), and 1 Himalayan (c^hc), resulting in a 1 chinchilla : 1 Himalayan ratio.

Quiz 5: Extensions and Modifications of Basic Principles

Interactions among the human ABO blood group alleles involve _ and _.

Suppose that extra fingers and toes are caused by a recessive trait, but it appears in only 60% of homozygous recessive individuals. Two heterozygotes conceive a child. What is the probability that this child will have extra fingers and toes?

A mother with blood type B has a child with blood type O. Give all possible blood types for the father of this child.

Crossing two yellow mice results in 2/3 yellow offspring and 1/3 nonyellow offspring. What percentage of offspring would you expect to be nonyellow if you crossed two nonyellow mice?

Polydactyly is the condition of having extra fingers or toes. Some polydactylous persons possess extra fingers or toes that are fully functional, whereas others possess only a small tag of extra skin. This is an example of:

The R locus determines flower color in a new plant species. Plants that are genotype RR have red flowers, and plants that are rr have white flowers. However, Rr plants have pink flowers. What type of inheritance does this demonstrate for flower color in these plants?

A mother with blood type AB has a child with blood type B. Give all possible blood types for the father of this child.

A mother with blood type A has a child with blood type A. Give all possible blood types for the father of this child.

In humans, blood types A and B are codominant to each other and each is dominant to O. What blood types are possible among the offspring of a couple of blood types AB and A?

A mother of blood type A gives birth to a child with blood type O. Which of the following could NOT be the blood type of the father?

A mother with blood type A has a child with blood type AB. Give all possible blood types for the father of this child.