Week 3 & 4 Progress Test 2

Lesch-Nyhan syndrome is a rare X-linked recessive disorder that produces severe mental retardation, spastic cerebral palsy, and self-mutilation. What is the probability that the first son of a woman whose mother's brother has Lesch-Nyhan syndrome will be affected?

1/2

In humans, the ABO blood type is under the control of autosomal multiple alles. Red-green color blindness is a recessive X-linked trait. If two parents who both have normal vision and type AB blood have a son, Jeff who is color blind and has AB blood, what is the probability that their second son, Adam will have normal vision and be type AB?

1/4

The parental cross between a rabbit with the Himalayan phenotype (genotype chch) and an albino rabbit (genotype cc) results in F1 rabbits that all have the Himalayan phenotype (genotype chc). If the resulting F1 rabbits are crossed, what proportion of the F2 offspring will be albino and what influences the hypomorphic ch allele to be unstable and result in the distinctive fur pattern?

1/4; temperature

How many Barr bodies would be present in white blood cells of an individual of karyotype 47, XXX?

2

The Manx cat has abnormal spinal development and no tail. The mutation is a dominant allele (M). For notation purposes, m refers to the wild-type allele that results in a tail. If a mating between two Manx cats produces three live offspring, what is the probability that two will be Manx and one will have a normal tail?

4/9

The mosquito, Culex pipens, has a diploid number of 6. How many chromosomes are present immediately after the homologous chromosomes have separated in anaphase 1?

6

The wild-type color of horned beetles is black, although other colors are known. A black beetle from a pure-breeding strain is crossed to a pure-breeding green female beetle. All of their F1 progeny are black. These F1 are allowed to mate at random with one another, and 320 F2 beetles are produced. The F2 consists of 179 black, 81 green, and 60 brown. Which phenotypic ratio could explain the F2 progeny?

9:4:3

Wild-type bacteria can grow on minimal medium. Four mutants that cannot grow on minimal medium but can grow on minimal medium supplemented with the nutrient "C" are isolated. It is suspected that metabolites A, B, and D are in the biochemical pathway for synthesis of C, so each mutant is tested for the ability to grow on minimal medium supplemented with these metabolites. Mutant 1: can grow on minimal medium supplemented with A, but not B or D Mutant 2: is unable to grow on minimal medium supplemented with A, B, or D Mutant 3: is able to grow on minimal medium supplemented with B or A, but not D Mutant 4: can grow on minimal medium supplemented with A, B, or D. Which of the following is NOT consistent with this information? -Mutant 3 will cause a build up of metabolite D -Mutant 1 will cause a build up of metabolite A -Mutant 2 blocks a step right before metabolite C -Mutant 3 blocks the conversion of metabolite D → metabolite B -Mutant 4 blocks a step before all 4 metabolites

Mutant 1 will cause a build up of metabolite A

Manx cats have no tails. When two Manx cats are bred together there is always a one third chance that a kitten will have a tail. When a Manx cat is bred to a cat with a normal tail there is a one-half chance that a kitten will have a tail. Which of the following is the best explanation for this? -The Manx phenotype is dominant epistatic. -The Manx genotype exhibits variable expression. -The Manx phenotype is dominant, but the allele is lethal when homozygous. -The Manx phenotype is a result of random X-inactivation. -The Manx phenotype is caused by gene interactions.

The Manx phenotype is dominant, but the allele is lethal when homozygous

Calvin Bridges's classic study of nondisjunction of sex chromosomes provided support for the chromosome theory of inheritance. Bridges performed crosses with fruit flies, tracking the sex-linked eye-color trait. Red-eyed males were crossed with white-eyed females. Which of the following is an accurate explanation of his findings?

The offspring were mostly white-eyed males and red-eyed females but 1/2000 offspring were white-eyed females (genotype XXY) or red-eyed males (genotype XO)

In sheep, coat color is influenced by two genes. Gene A influences pigment production, while gene B produces black or brown pigment. If two heterozygous white sheep were crossed and offspring were produced in a ratio of 12 white sheep to 3 black sheep to 1 brown sheep, what are the genotypes of the white offspring?

The white sheep could be A_B_ or A_bb

In domestic chickens, sex is determined by the ZW system. A Z-linked dominant allele for feather form has two alleles: B produces barred feathers, and b produces nonbarred feathers. If crossing barred males (roosters) and nonbarred females (hens) results in roosters and hens that are each 1/2 barred, and 1/2 nonbarred, which of the following is true of the genotype of the female parent?

Z^bW

During which stage of meiosis do chromosomes continue to condense, and homologous chromosomes enter synapsis?

Zygotene substage of prophase 1

The relationship of the I and H genes affects the expression of the ABO blood type in the following ways: genotype HH or Hh, AB produces blood type AB while genotype hh, AB produces blood type O. This is an example of

codominance

In his experiments, Mendel noted that when two traits are involved in a genetic cross, they are inherited independently of each other. The reason for this that

genes on different chromosomes separate during the formation of gametes

Which of the following is always true of X-linked dominant disorders? -If a normal male mates with a heterozygous female, then all of the daughters and sons will be affected. -The phenotype of the disease may skip generations and there is a greater prevalence of affected males. - If a normal male mates with a heterozygous female, then half of the sons will be affected and daughters will not show the disease phenotype. - If an affected male mates with a normal female, then all daughters and no sons will be affected. -If an affected male mates with a normal female, then neither daughters nor sons will show the disease phenotype.

if an affected male mates with a normal female then all daughters and no sons will be affected

In what condition is the phenotype of a heterozygous genotype an intermediate between the phenotypes of the homozygous genotypes and the genotype ratio is the same as the phenotypic ratio?

incomplete dominance

Most people with the dominant mutant polydactyly allele have extra digits, but at least 25% have the normal number of digits. What is the genetic explanation for this observation?

incomplete dominance

If an individual does not have functional phenylalanine hydroxylase, what metabolite will build up and what disease will result?

phenylalanine; phenylketonuria (PKU)

Starting with a population of genetically identical mice, you discover two new independent mutant strains in which all the animals have epileptic seizures. In both strains, you know that the epileptic seizures are due to a single DNA mutation. You cross a mutant mouse from one strain to a mutant mouse from the second strain and find that none of the offspring undergo spontaneous seizures. From this experiment, you would conclude that the two mutant strains of mice must have mutations in

two different genes