Exam 1 Genetics

A pregnant woman is a heterozygous carrier of a rare X-linked recessive genetic disease. The father does not have the disease. If they have a son, what is the probability that he will be affected by the disease? 0 0.25 0.5 The question does not provide enough information to determine the correct answer.

0.5

How many Barr bodies will there be in a typical somatic cell in a human XXY male?

1

How many Barr bodies will there be in a typical somatic cell in a human XXX genotype female?

2

Flower color in a plant you are studying is produced through a series of enzymatic reactions. In one step, controlled by the P locus, a yellow pigment is altered to be pink. There is a recessive p allele at that locus and the yellow-to-pink alteration is not made. Individuals with the pp genotype have yellow flowers. In the next step, controlled by the R locus, the dominant trait modifies the pink pigment to be a deep red. If you perform a PpRr x PpRr dihybrid cross, what do you expect the offspring phenotype ratio to be for red:pink:yellow flowers? 12:3:1 9:3:4 9:3:3:1 3:4:9

9:3:4

In a mammal model organism, the S locus controls sweat production, with the really-sweaty allele S being dominant over less-sweaty (s). The G locus controls the presence of body sweat glands, with Glands-present (G) being dominant over glands-absent (g). Individuals with no sweat glands (g) cannot sweat, regardless of their genotype at the S locus. Draw a Punnett Square for a dihybrid cross SsGg x SsGg (on scratch paper, or use the blank one in the pre-class PowerPoint file). What is the expected offspring phenotype ratio, Really-sweaty : Less-sweaty : No sweat? 12:3:1 9:3:4 9:6:1 9:4:3

9:3:4

In rabbits, solid-colored fur (F) is dominant over spotted fur (f). A male solid-white rabbit is known to come from a line that is true-breeding for solid-color fur. If he is crossed with a spotted-fur female, what name to we give to that cross? A monohybrid cross A test cross A complete cross An F2 cross

A monohybrid cross

Which of the following is correct about sister chromatids and homologous chromosomes? A pair of sister chromatids are essentially identical to each other; a pair of homologous chromosomes almost always have multiple differences in the DNA sequences. A pair of homologous chromosomes are essentially identical to each other; a pair of sister chromatids almost always have multiple differences in the DNA sequences. A pair of sister chromatids have the same set of genes; a pair of homologous chromosomes have different genes. "Homologous chromosomes" is another name for sister chromatids.

A pair of sister chromatids are essentially identical to each other; a pair of homologous chromosomes almost always have multiple differences in the DNA sequences.

In rabbits, straight ears (S) are dominant over floppy ears (s). We have a straight-eared rabbit, but we do not know if it is from a true-breeding line or not. If we cross him to a floppy-eared girl rabbit, what kind of cross would that be? A test cross A heterozygous cross An incomplete cross A monohybrid cross

A test cross

A black square in a pedigree represents: An unaffected female An affected female An unaffected male An affected male

An affected male

In rabbits, solid-colored fur (F) is dominant over spotted fur (f), and straight ears (S) is dominant over floppy (s). These two genes are on different chromosomes and follow Mendel's Law of Independent Assortment. You began with a dihybrid P-generation cross, FFSS x ffss. You want to use a Punnett square to predict what is expected if you were to cross two of the F1 offspring to each other. Which of the following is not a gamete genotype that could be produced by one of the F1 individuals? fS FS FF fs

FF

In a somatic cell in a human triple-X female, there will be one Barr body and 2 active X chromosomes. True False

False

In rabbits, solid-colored fur (F) is dominant over spotted fur (f). A male white rabbit without spots and crosses it with a female white rabbit without spots. Some of the baby rabbits have spots. What is the genotype of the male parent? ff Ff FF It could be either FF or Ff

Ff

The red pigment required for red flower color in a plant is produced by a pathway of two enzymes. Enzyme A converts a precursor into a colorless intermediate, then Enzyme B converts the intermediate compound into red pigment. At the molecular level, the a allele produces a non-functional form of Enzyme A, and the b allele produces a non-functional form of Enzyme B. These two genes together exhibit Duplicate Recessive epistasis, and show a 9:7 phenotype ratio in a dihybrid cross. Which of the following explains why a plant could have full Enzyme B activity (from a BB genotype), and yet produce only white flowers? If the plant has the genotype aa, no intermediate product will be produced, so Enzyme B has nothing to work on. If the plant has the aa genotype, Enzyme B is physically inhibited by the mutant Enzyme A molecules. The question is not correctly stated - a plant with the genotype BB will produce red flowers. Functional Enzyme A is required in order for Enzyme B to be produced.

If the plant has the genotype aa, no intermediate product will be produced, so Enzyme B has nothing to work on.

Amniocentesis Invasive Non-invasive

Invasive

Chorionic Villus Sampling Invasive Non-invasive

Invasive

Pre-implantation Genetic Diagnosis Invasive Non-invasive

Invasive

Maternal Blood Screening Invasive Non-invasive

Non-invasive

Ultrasonography Invasive Non-invasive

Non-invasive

In mice, bent-tail is a dominant mutation located on the X-chromosome. A bent-tailed male is crossed to a heterozygous female. What fraction of the female offspring will have a normal tail? All 1/2 1/4 None

None

Which of the following is correct about a monohybrid cross for a gene at which the two alleles show incomplete dominance? The F1 offspring will have phenotypes that cannot be distinguished from those of one of the parental genotypes. The F2 genotype ratio will be 3:1 The F2 phenotype ratio will be 1:2:1 An F2 generation can only be produced if the species is capable of self-fertilization.

The F2 phenotype ratio will be 1:2:1

A common form of human red-green color-blindness is X-linked. Normal color vision is dominant and color-blind is recessive. Which of the following must be true, in order for a woman to have a color-blind daughter? The woman is herself color-blind. The father of the woman's daughter is color blind. All of her sons will be color-blind. The woman's mother was color-blind.

The father of the woman's daughter is color blind.

Which of the following is true about epistasis? Epistatic interactions are limited to two genes. Two genes that are epistatic are said to be genetically linked. Two genes that have an epistatic interaction can assort independently. Two genes that are epistatic are also said to be pleiotropic.

Two genes that have an epistatic interaction can assort independently.

In most mammals, the identity of the single active X chromosome is determined at zygote formation. a fairly early stage of development. every mitosis. birth.

a fairly early stage of development.

A defining feature in a pedigree of a trait that tells you it must be dominant is seeing a pair of affected parents have at least one unaffected offspring. a pair of affected parents have at least one affected offspring. a pair of unaffected parents have at least one affected offspring. a pair of unaffected parents have at least one unaffected offspring.

a pair of affected parents have at least one unaffected offspring.

In Drosophila melanogaster, the white gene is located on the X chromosome. + indicates the normal, dominant allele, and it results in normal red eye color. The recessive mutant allele is called w (a lowercase w) The very first mutation found in Drosophila was a white-eyed male. When that male was mated to a true-breeding red-eyed female, the offspring would be all red-eyed females and white-eyed males. be 1/2 red-eyed and 1/2 white-eyed, for both sexes. red-eyed females red-eyed and 1/2 of the males red-eyed and 1/2 of the males white-eyed. all have red eyes.

all have red eyes.

A white and a red flower are crossed, and all of the offspring have both red and white stripes. This is an example of: dominance incomplete dominance epistasis codominance

codominance

A male mammal receives an X chromosome from after recombination, so partly his mother's and partly his father's. either his mother or his father. his mother only. his father only.

his mother only.

In a species of flowering plant, AA individuals are 10" tall, Aa individuals are 9" tall and aa individuals are 4" tall. This is a case of co-dominance. incomplete dominance. epistasis. complete dominance.

incomplete dominance.

Which of the following are loaded into a developing oocyte (egg cell) by the mother, in order to allow the new embryo to begin protein synthesis before it has begun to transcribe its own genes? DNA viruses mRNA

mRNA

pair of unaffected parents have an affected child. The trait is autosomal recessive. autosomal dominant. dominant, but we cannot tell from this information if it is autosomal or X-linked. recessive, but we cannot tell from this information if it is autosomal or X-linked.

recessive, but we cannot tell from this information if it is autosomal or X-linked.

At the level important to blood banks, there are three "ABO" phenotypes (Type-A, Type-B and Type-O blood). The genotypes AA and AO both have the phenotype "Type-A blood". This demonstrates that the ABO system involves epistasis. the A allele is completely dominant to the O allele. the ABO system exhibits incomplete dominance. the A allele is probably recessive to the B allele.

the A allele is completely dominant to the O allele.

The term 'epistasis' refers to a situation in which two genes share a single allele. two independent genes both have alleles with incomplete dominance. the genotype at one locus affects the phenotype observed at a different locus. a single gene has more than two alleles.

the genotype at one locus affects the phenotype observed at a different locus.

In humans, sex is most directly determined by the presence of specific genes normally found only on the Y-chromosome. the ratio of X-chromosomes to Y-chromosomes. the number of X-chromosomes. the ratio of X-chromosomes to autosomes.

the presence of specific genes normally found only on the Y-chromosome.

A trait can be classified as definitely dominant if two affected parents have an affected offspring. two unaffected parents have an unaffected offspring. two affected parents have an unaffected offspring. two unaffected parents have an affected offspring.

two affected parents have an unaffected offspring.

In a certain plant yellow fruit (Y) is dominant to white fruit (y). The only possible cross that would be expected to result in only white-fruited offspring is x .

yy x yy