ch 14 Flashcards
Mendel studies seven different traits in the garden pea. What genetic term is used to describe an observable trait, such as those studied by Mendel?
C) Phenotype
Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This ratio suggests that ______.
D) The parents were both heterozygous for the particular trait.
When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?
C) 50%
Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that ______.
C) Traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1 generation.
Albinism is an autosomal (i.e., not sex–linked) recessive trait. A man and woman are both of normal pigmentation and have one child out of three who is albino (without melanin pigmentation). What are the genotypes of the albino’s parents?
C) Both parents must be heterozygous.
Different ratios occurr in crosses with single gene pairs or two gene pairs. What types of ratios are likely to occur in crosses dealing with a single gene pair?
C) 3:1, 1:1, 1:2:1
A black guinea pig crossed with an albino guinea pig produced 12 black offspring. When the albino was crossed with a second black animal, six blacks and six albinos were obtained. What is the best explanation for the genetic situation?
A) Albino is recessive, black is dominant.
When Mendel crossed yellow-seeded and green-seeded pea plants, all the offspring were yellow-seeded. When he took these F1 yellow-seeded plants and crossed them to green-seeded plants, what genotypic ratio was expected?
D) 1:1
Why did the F1 offspring of Mendel’s classic pea cross always look like one of the two parental varieties?
D) One allele was dominant
What do we mean when we use the terms “monohybrid cross” and “dihybrid cross?”
C) A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied.
How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?
B) 8
Mendel crossed yellow-seeded and green-seeded pea plants, and then allowed the offspring to self-pollinate to produce an F2 generation. The results were as follows: 6022 yellow and 2001 green (8023 total). The allele for green seeds has what relationship to the allele for yellow seeds?
C) Recessive
Suppose two AaBbCc individuals are mated. Assuming that the genes are NOT linked, what fraction of the offspring are expected to be homozygous recessive for the three traits?
D) 1/64
The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment, most probably indicates which of the following?
D) All of the genes controlling the traits behaved as if they were on different chromosomes.
When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result?
B) The gene evolved is on the X chromosome.
