CH 14

Pea plants were particularly well suited for use in Mendelʹs breeding experiments for all of the following reasons except that

• peas show easily observed variations in a number of characters, such as pea shape and flower color.

• it is possible to control matings between different pea plants.

• it is possible to obtain large numbers of progeny from any given cross.

• peas have an unusually long generation time.

What is the difference between a monohybrid cross and a dihybrid cross?

• A monohybrid cross involves a single parent, whereas a dihybrid cross involves twoparents.

• A monohybrid cross produces a single progeny, whereas a dihybrid cross producestwo progeny.

• A dihybrid cross involves organisms that are heterozygous for two characters and amonohybrid only one.

• A monohybrid cross is performed for one generation, whereas a dihybrid cross isperformed for two generations.

A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates

• the blending model of genetics.

• true-breeding.

• dominance.

• a dihybrid cross.

The F1 offspring of Mendelʹs classic pea cross always looked like one of the two parentalvarieties because

• one phenotype was completely dominant over another.

• each allele affected phenotypic expression.

• the traits blended together during fertilization.

• no genes interacted to produce the parental phenotype.

What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?

• There is considerable genetic variation in garden peas.

• Traits are inherited in discrete units, and are not the results of ʺblending.ʺ

• Recessive genes occur more frequently in the F1 than do dominant ones.

• Genes are composed of DNA.

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

• 4

• 8

• 16

• 32

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This suggests

• that the parents were true-breeding for contrasting traits.

• incomplete dominance.

• that a blending of traits has occurred.

• that the parents were both heterozygous.

Two characters that appear in a 9:3:3:1 ratio in the F 2 generation should have which of thefollowing properties?

• Each of the traits is controlled by single genes.

• The genes controlling the characters obey the law of independent assortment.

• Each of the genes controlling the characters has two alleles.

• Sixteen different phenotypes are possible.

A sexually reproducing animal has two unlinked genes, one for head shape ( H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

• HT

• Hh

• HhTt

• T

It was important that Mendel examined not just the F 1 generation in his breeding experiments, but the F2 generation as well, because

• he obtained very few F1 progeny, making statistical analysis difficult.

• parental traits that were not observed in the F1 reappeared in the F2.

• analysis of the F1 progeny would have allowed him to discover the law ofsegregation, but not the law of independent assortment.

• the dominant phenotypes were visible in the F2 generation, but not in the F1. E) many of the F1 progeny died.