Question 1

In Mendel's experiments with pea plants, what is the expected phenotypic ratio in the F2 generation when two heterozygous purple-flowered plants (Pp) are crossed?

Accepted Answer

3 purple : 1 white

Question 2

Which of the following best explains why a carrier of a recessive genetic disorder does not show symptoms of the disorder?

Accepted Answer

In a recessive disorder, only a single functioning allele is necessary to determine a normal phenotype.

Question 3

If a person with type-B blood (genotype $$I^B i) $$has children with a person with type-AB blood ($$I^A I^B$$), what blood types could their children have?

Accepted Answer

Type AB, Type A and Type B

Question 4

Which of the following statements about alleles is correct?

Accepted Answer

They have different sequences of DNA nucleotides.

Question 5

A cross is made between parents with genotypes AABB and aabb. If there were sixteen offspring, how many of them would be expected to exhibit both dominant characteristics?

Accepted Answer

100%

Question 6

In guinea pigs, B = black, b = brown, S = short hair and s = long hair. A homozygous black, heterozygous short hair (BB Ss) is mated to a homozygous brown, heterozygous short hair (bb Ss). Which of the following describes the probability of offspring?

Accepted Answer

All of the above.

Question 7

Suppose a white-furred rabbit breeds with a black-furred rabbit and all of their offspring have gray fur. What does the gene for fur color in rabbits appear to be an example of?

Accepted Answer

Incomplete dominance

Question 8

Which of the following offspring phenotypes could a homozygous black, homozygous short hair guinea pig produce?

Accepted Answer

Black short hair guinea pig.

Question 9

In horses, T = trotter, t = pacer, B = black and b = chestnut. If a heterozygous dihybrid in both traits (TtBb) is mated with a chestnut pacer (ttbb), which of the following describes the probability of offspring phenotypes?

Accepted Answer

One black trotter, one chestnut pacer, one black pacer, one chestnut trotter.

Question 10

Which children could not occur if two parents were type A blood?

Accepted Answer

Type AB.

Question 11

Which children could not have a parent who is type AB?

Accepted Answer

Type O.

Question 12

Skin color in humans becomes darker by the number of dominant alleles; AABBCC have the darkest skin and aabbcc have the lightest skin. Place these genotypes in sequence according to the color of skin expected for each, from darkest to lightest: AaBBCC, AaBBCc, AaBbCc, AAbbcc, aabbCc.

Accepted Answer

AaBBCC \u003e AaBBCc \u003e AaBbCc \u003e AAbbcc \u003e aabbCc

Question 13

In a dihybrid cross between two heterozygous pea plants (YyRr x YyRr), what is the expected phenotypic ratio for the F2 generation?

Accepted Answer

$$9:3:3:1$$

Question 14

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the phenotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

Accepted Answer

1 black : 1 orange

Question 15

Which of the following best describes Mendel's law of segregation?

Accepted Answer

Each gamete contains a single allele of each gene.

Question 16

Galactosemia is a human genetic disorder caused by a deficiency of the enzyme GALT. If both parents are heterozygous carriers, what is the probability that their next child will have galactosemia?

Accepted Answer

$$\frac{1}{4}$$

Question 17

Which of the following is an example of codominance in humans?

Accepted Answer

ABO blood group, where both $$I^A$$ and $$I^B$$ alleles are expressed in type AB individuals.

Question 18

Which of the following best explains the difference between quantitative characters and the characters Mendel studied in peas?

Accepted Answer

Quantitative characters are due to polygenic inheritance, the additive effects of two or more genes on a single phenotypic character. A single gene affected all but one of the pea characters studied by Mendel.

Question 19

In a testcross, what is the purpose of crossing an individual with a dominant phenotype but unknown genotype with a homozygous recessive individual?

Accepted Answer

To determine whether the individual is homozygous or heterozygous for the dominant allele.

Study Guide: Mendelian Genetics and Beyond

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