PCRQ M Week 2

In human populations, there are many alleles of the genes affecting eye color, not just two.

Humans can have many different eye colors ranging from blue to brown. Which answer option could explain this array of different eye colors? 1. In human populations, there are many alleles of the genes affecting eye color, not just two. 2. Some alleles are dominant in some people and recessive in others. 3. The genes affecting eye color must be linked and located near each other on a chromosome. 4. The genes affecting eye color must produce pigments that break down over time.

The trait was absent in the son's children because they each carried at least one dominant allele.

In the pedigree shown, a set of parents (at the top) have three children—two daughters and a son. That son (on the right-hand side of the pedigree) has a family in which none of the children are affected. However, one of his grandchildren is affected. How could the trait disappear in one generation and reappear in the next? 1. The trait was absent in the son's children because they each carried at least one dominant allele. 2. In the generation when the trait is absent, the trait is recessive. In the generation when it appears, the trait is dominant. 3. When the trait reappears in the grandchildren, it must have resulted from a brand-new mutation in the gene that did not exist in the parents or grandparents. 4. The gene must have been unstable and switched between being mutant and not being mutant.

anaphase I

Recall that alleles of a single gene will segregate from one another during anaphase I. When do alleles for two different genes—located in two different chromosomes—segregate? 1. anaphase I 2. anaphase II 3. metaphase I 4. metaphase II

both the multiplication rule and the principle of independent assortment.

Recall that in Mendel's work, mating between yellow wrinkled, seed-producing plants and plants that produced smooth green seeds resulted in a ratio of 9:3:3:1 for progeny phenotypes. This observed ratio can be explained by: 1. the principle of independent assortment. 2. the addition rule. 3. both the multiplication rule and the principle of independent assortment. 4. incomplete dominance. 5. the multiplication rule. 6. both the addition rule and the principle of independent assortment. 7. both the addition rule and multiplication rule.

epistasis

The breeding example of White Leghorn chickens and White Wyandotte chickens, in which more than one gene controls expression of another gene that causes pigment production, is an example of _____ interaction between genes. 1. incomplete dominance 2. epistasis 3. recessive 4. variable expressivity

dominant and is seen in heterozygous or homozygous dominant individuals.

While doing a pedigree analysis of a royal family from the ancient Mayan empire, you notice that a prince with a genetic disease married a person from outside the royal family without a history of the disease in her family. Of their six children, two have the disease and four were not affected. The prince's mother and father also had this disease. If this disease is controlled by a single gene, then the most likely explanation for its occurrence in the children would be that the disease is: 1. a spontaneous mutation. 2. recessive and is only seen in homozygous recessive individuals such as the two affected children. 3. dominant and is seen in heterozygous or homozygous dominant individuals. 4. dominant and is only seen in homozygous dominant individuals.

1/16

You are given two populations of true‑breeding tomato plants with two traits that assort independently. Using the multiplication rule, how many of the F2 progeny would you expect to have a recessive phenotype for both traits? a. 9/16 b. 4/16 c. 3/16 d. 1/16

25%

You are given two true‑breeding groups of gerbils. The gerbils in the first group have black fur and curly tails; the gerbils in the second group have yellow fur and straight tails. When you produce an F1 generation, you see only gerbils with black fur and curly tails. When you produce an F2 generation, you see that 75% of the gerbils have black fur and 25% have yellow fur. You also see that 25% of the gerbils have straight tails and 75% have curly tails. If the single alleles responsible for coat color and tail appearance sort independently, how many of the black gerbils in this generation are expected to have straight tails? a. 25% b. 50% c. 75% d. 100%