Answer key to Quiz 3:

1. Conditions such as Down syndrome and Klinefelter syndrome result when certain chromosomes (but not an entire set) are present in extra copies or are deficient in number. This type of chromosomal abnormality is called:
   a. aneuploidy
2. Many plants (but few animals) have more than two complete chromosome sets. This type of chromosomal aberration is called:
   d. polyploidy
3. A type of chromosome alteration which results when a chromosomal fragment becomes attached to a non-homologous chromsome is called a:
   d. translocation
4. An organism having a pair of identical alleles for a character is said to be ? for the gene controlling that character.
   c. homozygous
5. In humans, the free-earlobe trait (E) is dominant to attached earlobes (e). Erasmus, who has free earlobes, marries a woman with attached earlobes. They have a child with attached earlobes. Erasmus' most likely genotype is:
   b. Ee
6. In garden peas, green pod color (G) is dominant to yellow pod color (g). If two pea plants that are heterozygous for pod color are crossed, what percentage of the offspring would be expected to have yellow pods?
   b. 25 percent
7. The separation of alleles into separate gametes during meiois is known as Mendel's:
   b. law of segregation
8. In a dihybrid cross (e.g., YyRr x YyRr), the offspring will exhibit all possible combinations of traits in a 9:3:3:1 phenotypic ratio. This result is consistent with:
   b. Mendel's law of independent assortment
9. When red snapdragons are crossed with white ones, the resulting offspring have pink flowers. This is an example of:
   a. incomplete dominance
10. The situation where a gene at one locus alters the phenotypic expression of a gene at a different locus is called:
    b. epistasis