Practice Exam Questions Week 2 Flashcards
The pedigree shown here pertains to a trait due to a rare, X-linked recessive mutation.
Individual 1 has an affected grandfather, but the genotypes and phenotypes of individuals 1–4 are unknown. What is the probability that individual 1 is heterozygous? What is the probability that individual 3 is heterozygous? What is the probability that individual 4 is affected?
1; 1/4; 1/4
1; 1/2; 1/2
1/2; 1/4; 1/2
1/2; 1/2; 1/2
1/2; 1/4; 1/4
1/2; 1/4; 1/4
An individual who is heterozygous for two linked genes (with alleles A, a and B, b) is crossed with an a b/a b individual, and among the progeny are the following:
14 A B/a b
36 A b/a b
34 a B/a b
16 a b/a b
What is the frequency of recombination?
- 30
- 35
- 40
- 60
- 70
0.30
Hemophilia is a sex-linked recessive trait in humans. If a carrier female (heterozygous for the trait) mated with a nonaffected male, what would be the expected outcome(s)?
None of the offspring would have hemophilia.
None of the daughters would have hemophilia.
Half the daughters would have hemophilia.
Half the sons would have hemophilia.
None of the daughters would have hemophilia, and half of the sons would have hemophilia.
None of the daughters would have hemophilia, and half of the sons would have hemophilia.
X-linked genes show crisscross inheritance because males:
get their Y chromosome from their father.
get their X chromosome from their mother.
transmit their Y chromosome to their sons.
transmit their X chromosome to their daughters.
get their Y chromosomes from their father and transmit their Y chromosomes to their sons.
get their X chromosomes from their mother and transmit their X chromosomes to their daughters.
get their X chromosomes from their mother and transmit their X chromosomes to their daughters.
Suppose that certain genes related to the eye, ear, nose, and throat are present in two autosomes, and each of these genes has multiple alleles. The eye and ear genes have a recombination frequency of 25%, and the nose and throat genes have a recombination frequency of 35%. As a genetic counselor, you are examining these genes in a couple who are interested in having children soon. Simplified illustrations of the mother’s and father’s genotypes are below.
Assuming equal frequencies of recombination in females and males, which combination would be more common in offspring?
nose3 throat1 in one chromosome, nose3 throat1 in the other chromosome
nose3 throat1 in one chromosome, nose6 throat2 in the other chromosome
nose6 throat2 in one chromosome, nose6 throat2 in the other chromosome
None. All possible combinations would be equally represented in offspring.
None. All possible combinations would be equally represented in offspring.
What proportion of the couple’s offspring will inherit eye7 ear4 from the mother?
100%
75%
37.5%
25%
12.5%
37.5%
If the couple’s potential child inherits the eye7 allele from the mom, what is the chance of the child also inheriting the eye8 allele from the father?
100%
75%
50%
25%
0%
0%
What proportion of the couple’s offspring will be eye7 eye7/nose3 nose3?
1/4
1/2
1/8
1/16
1/32
1/16
The pedigree shown here pertains to a trait due to a rare, X-linked recessive mutation.
Individual 1 has an affected father, but the genotypes and phenotypes of individuals 1–4 are unknown. What is the probability that individual 1 is heterozygous? What is the probability that individual 3 is heterozygous? What is the probability that individual 4 is affected?
1/2; 1/4; 1/4
1/2; 1/4; 1/2
1; 1/4; 1/2
1; 1/2; 1/4
1; 1/2; 1/2
1; 1/2; 1/2
Considering an X-linked dominant trait, if an unaffected woman and an affected man decide to have children, which of the following statements is TRUE about the possibilities for their children?
Their sons are expected be heterozygous for the associated gene.
Their daughters are expected be heterozygous for the associated gene.
All their children, whether male or female, are expected to show the dominant trait.
All of their sons are expected to show the dominant trait.
Their daughters are not expected to show the dominant trait.
Their daughters are expected be heterozygous for the associated gene.
Red-green color blindness is due to a mutant gene in the X chromosome. An XX female with normal color vision and an XY male with normal color vision have a child with karyotype XXY who is color blind. The likely explanation is that the:
father was heterozygous for the color-blindness mutation.
mother was heterozygous for the color-blind mutation.
father had CNV of the color-blind mutation.
mother had CNV of the color-blind mutation.
None of the other answer options is correct.
mother was heterozygous for the color-blind mutation.
An individual that is heterozygous for two linked genes has the genotype A b/a B, which means that the A and b alleles are in one chromosome and the a and B alleles in the homologous chromosome. Among the products of meiosis listed below, which are the recombinant types? (Select all that apply.)
A B
A b
a B
a b
A B
a b
Given equal probabilities of the birth of a boy or girl, what is the probability that a group of four siblings includes all boys? All girls? All boys or all girls?
1/8; 1/16; 3/8
1/16; 1/8; 3/8
1/16; 1/16; 1/64
1/16; 1/16; 1/8
1/16; 1/16; 1/8
An individual is heterozygous for two linked genes, but whether its genotype is A B/a b or A b/a B is not known. The individual is crossed with an a b/a b individual, and among the progeny are the following:
16 A B/a b
54 A b/a b
46 a B/a b
24 a b/a b
These results imply that the genotype of the doubly heterozygous parent was A B/a b.
True
False
False
