Topic 4

In pea plants..

3/8

All of the following contribute to genetic recombination or variation in offspring EXCEPT

gene linkage

If a person with type O blood were to have children with a person with type AB blood, which of the following represents the best prediction of the ratio of possible blood types for their offspring?

1 IAi: 1 IBi

A couple has six children, all daughters. If the woman has a seventh child, what is the probability that the seventh child will be a daughter?

1/2

If genes R and S are on two different chromosomes and the probability of allele R segregation into a gamete is 1/4, while the probability of allele S segregating into a gamete is 1/2, what is the probability that both will segregated into the same gamete?

1/4 X 1/2

A yeast cell in the early portion of interphase of meiotic cell..

12

In fruit flies...

17%

In llamas, coat color is controlled by a gene that exists in two allelic forms. If a homozygous yellow llama is crossed with a homozygous brown llama, the offspring have gray coats. If two of the gray-coated offspring were crossed, what percentage of their offspring would have brown coats?

25%

In cucumbers, warty (W) is dominant over dull (w), and Green (G) is dominant over orange (g). A cucumber plant that is homozygous for warty and green is crossed with one that is homozygous for dull and orange. The F1 generation is then crossed. If 144 offspring are in the F2 generation, which of the following is closest to the number of dull green cucumbers expected?

28

In some plants, a tree breeding...

3 axial red, 6 axial pink, 3 axial white, 1 terminal red, 2 terminal pink, 1 terminal white

A cell with a diploid number of 6 could produce gametes with how many different combinations of maternal and paternal chromosomes?

8

In pea plants, pod color may be green or yellow...

9 green inflated, 3 green constricted, 3 yellow inflated, 1 yellow constricted

If a woman has type A blood, and her child has type O blood, the father must have which of the following blood types?

A, B, or O

A black guinea pig crossed with an albino guinea pig produced twelve 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 this genetic situation?

Albino is recessive; black is dominant. first cross: Bb second cross: 1/2B 1/2b. offspring 1/2Bb 1/2bb

Given the following recombination frequencies, what is the correct order of the genes on the chromosome? A-B 8; A-C 28; A-D 25; B-C 20; B- D 33

D A B C

In rabbits, the gene for short hair (S) is dominant... what is the most likely genotype of the parent rabbits in this cross?

SsGg X SSGg

Which of the following explains a significantly low rate of crossing over between two genes?

The genes are located very close together on the same chromosome.

Two yellow mice with the genotype Yy are mated. After many offspring 2/3 are yellow and 1/3 are not yellow. Mendelian genetics dictates that this cross should make offspring that were 1/4 YY (yellow), 1/2 Yy (yellow), and 1/4 yy (not yellow). What is the most likely conclusion from this experiment?

The mice did not bear enough offspring for the ratio calculation to be specific

In humans, hemophilia is a sex-linked recessive trait. If a man and a woman have a son who is affected with hemophilia, which of the following is definitely true?

The mother carries an allele for hemophilia

In the given pedigree, circles represent females and square represents males.... which pattern of inheritance best explains the pedigree for this trait?

autosomal dominant

In regard to the baby's colorblindness, a sex-linked recessive trait, you explain that

because colorblindness is sex-linked, a son can inherit colorblindness if his mother has the recessive colorblindness allele.

As a genetic counselor, you would explain to the parents that

each parent could have contributed one recessive allele, resulting in type O blood.

Chromosome number is reduced to haploid in meiosis. What must occur to restore the diploid chromosome number?

fertilization

If these four cells resulted from cell division of a single cell with diploid chromosome number 2n = 4, what best describes what just occurred?

nondisjunction

X-linked conditions are more common in men than in women because

the sex chromosomes are more active in men than in women