Khan Chromosomal Inheritance Questions
A color-blind man marries a woman with no family history of color-blindness. What is the likelihood that they have a color-blind daughter? Choose 1 answer: Choose 1 answer: (Choice A) A 0% (Choice B) B 25% (Choice C) C 50% (Choice D) D 100%
(Choice A) A 0% If the mother can only pass on color-vision alleles, there is 0% chance of a daughter (2 X chromosomes) to be color-blind.
Which of the following statements about synaptonemal complexes is not true? Choose 1 answer: Choose 1 answer: (Choice A) A They act as a support structure (Choice B) B They form during synapsis (Choice C) C They are made up of functional RNA and protein (Choice D) D They form between sister chromatids
(Choice C) C They are made up of functional RNA and protein
What of the following provides the best evidence that DNA is the genetic material? Choose 1 answer: Choose 1 answer: (Choice A) A Biomolecular composition of chromosomes (Choice B) B Presence of DNA in all cells (Choice C) C Transformation using heat-inactivated bacteria (Choice D) D Mechanism of semi-conservative DNA replication
(Choice C) C Transformation using heat-inactivated bacteriaIf heat-inactivated bacteria can transform (transfer genetic information to) other bacteria, protein cannot be the genetic material. Thus, DNA must be the genetic material.
Sickle-cell anemia is an autosomal recessive genetic disorder whose carriers have a genetic advantage in surviving malaria. If 42% of the population is malaria resistant, but not anemic, what is frequency of the sickle-cell allele? Choose 1 answer: Choose 1 answer: (Choice A) A 21% (Choice B) B 49% (Choice C) C 9% (Choice D) D 30%
(Choice D) D 30% If 2pq = .42, then pq = .21. Since p + q = 1, p and q must be .3 and .7. Only 30% is available as a choice, so that must be the allelic frequency of the sickle-cell allele.
Which of the following population's coat/fur/feather color gene is most likely to be in Hardy-Weinberg equilibrium? Choose 1 answer: Choose 1 answer: (Choice A) A A pack of wolves in a zoo (Choice B) B Lab rats being bred by scientists (Choice C) C A flock of moths that must blend in with their environment to survive (Choice D) D A flock of seagulls that feeds on one type of fish
(Choice D) D A flock of seagulls that feeds on one type of fish A flock of seagulls that eats only type of fish may be under selection for traits related to catching that type of fish, but that would likely not have an effect on the seagulls' coat color gene, which thus should be in Hardy Weinberg equilibrium.
Problem A gene, TALL, has recently been discovered that helps control the height that people will reach and results in taller than average height. Which of the following statements about this gene's heritability are true? Choose 1 answer: Choose 1 answer: (Choice A) A If TALL has 25% penetrance, it must be autosomal recessive (Choice B) B If TALL has constant expressivity, every cell in the body will express the TALL protein (Choice C) C If TALL has 50% penetrance, then only half the population has the TALL gene (Choice D) D If TALL has variable expressivity, everyone with the TALL gene will be tall
(Choice D) D If TALL has variable expressivity, everyone with the TALL gene will be tall The concept of expressivity depends on the gene having 100% penetrance, so if TALL has variable expressivity then everyone with the TALL gene is of above average height.
Many people have DNA mutations that go unnoticed. What type of mutation is most likely to have no effect on phenotype? Choose 1 answer: Choose 1 answer: (Choice A) A Chromosomal (Choice B) B Deletion (Choice C) C Frameshift (Choice D) D Missense
(Choice D) D Missense
A researcher was doing test crosses on mice, but forgot which mice he had bred together. When the litter was born, every mouse had black eyes, and half had brown fur. What was the genotype of the parent mice? R = red fur; r = brown fur B = black eyes; b = brown eyes Choose 1 answer: Choose 1 answer: (Choice A) A RrBB x Rrbb (Choice B) B RrBb x RrBb (Choice C) C RrBb x rrBB (Choice D) D rrBb x RRBB
A cross between a RrBb and an rrBB mouse is the only option that would give a litter with only black eyes and a 50/50 split on fur color.
The results of a linkage analysis of genes A, B, C, and D have just come in from the lab. In what order are the alleles found on the chromosome? Gene Combination Recombination Frequency A/B 3.0% A/C 5.0% B/C 8.0% A/D 8.0% C/D 3.0% (Choice A) A ACDB (Choice B) B ABCD (Choice C) C CDAB (Choice D) D DCAB
D. DCAB A/B and C/D have the lowest recombination frequencies, so each pair must be next to each other. B/C and A/D have the same recombination frequency, so they must be equally separated. At this point, the options are ABDC or BACD. We can see that A/C are closer to each other than B/C or A/D, so we know that the proper order must be BACD or DCAB in reverse order.