AP Biology CH 15 self quiz

You design Drosophila crosses to provide recombination data for gene a, which is located on the chromosome shown in the figure below. Gene a has recombination frequencies of 14% with the vestigial-wing locus and 26% with the brown-eye locus. Approximately where is a located along the chromosome?

about one-third of the distance from the vestigial-wing locus to the brown-eye locus

A man with hemophilia (a recessive, sex-linked condition) has a daughter of normal phenotype. She marries a man who is normal for the trait. What is the probability that a daughter of this mating will be a hemophiliac? Express your answer as a fraction using the slash symbol and no spaces (for example, 1/24), or as a whole number.

0; 1/2, 1/16

Red green color is caused by a sex linked recessive allele. A color blind man marries a woman with normal vision whose father was color blind. What is the probability that they will have a color blind daughter? What is the probability that their first son will be color blind?

1/4 for each daughter 1/2 chance for first son

A wild-type fruit fly (heterozygous for gray body color and normal wings) is mated with a black fly with vestigial wings. The offspring have the following phenotypic distribution: wild-type 778 black-vestigial 785 black-normal 158 gray-vestigial 162 What is the recombination frequency between these genes for body color and wing size? Express your answer as a percentage.

17%

Two genes of a flower, one controlling blue (B) versus white (b) petals and the other controlling round (R) versus oval (r) stamens, are linked and are 10 map units apart. You cross a homozygous blue-oval plant with a homozygous white-round plant. The resulting F1 progeny are crossed with homozygous white-oval plants, and 1,000 F2 progeny are obtained. How many F2 plants of each of the four phenotypes do you expect? _____ blue-oval : _____ white-round : _____ blue-round : _____ white-oval Express your answer as four whole numbers separated by colons (for example, 400:300:200:100).

450:450:50:50

In another cross, a wild-type fruit fly (heterozygous for gray body color and red eyes) is mated with a black fruit fly with purple eyes. The offspring are as follows: wild type, 721; black-purple, 751; gray-purple, 49; black-red, 45. What is the recombination frequency between these genes for body color and eye color? Using information from problem 4, what fruit flies (genotypes and phenotypes) would you mate to determine the sequence of the body-color, wing-size, and eye-color genes on the chromosome?

6%. Wild type (heterozygous for normal wings and red eyes) × recessive homozygote with vestigial wings and purple eyes

Banana plants, which are triploid, are seedless and therefore sterile. Which is the most likely explanation for this phenomenon?

Because they are triploid, bananas cannot generate gametes because homologous pairs cannot line up during meiosis.

A space probe discovers a planet inhabited by creatures who reproduce with the same hereditary patterns seen in humans. Three phenotypic characters are height (T = tall, t = dwarf), head appendages (A = antennae, a = no antennae), and nose morphology (S = upturned snout, s = downturned snout). Since the creatures are not "intelligent," Earth scientists are able to do some controlled breeding experiments, using various heterozygotes in testcrosses. For tall heterozygotes with antennae, the offspring are: tall-antennae, 46; dwarf-antennae, 7; dwarf-no antennae, 42; tall-no antennae, 5. For heterozygotes with antennae and an upturned snout, the offspring are: antennae-upturned snout, 47; antennae-downturned snout, 2; no antennae-downturned snout, 48; no antennae-upturned snout, 3. Calculate the recombination frequencies for both experiments.

Between T and A, 12%; between A and S, 5%

Using the information from problem 11, scientists do a further test cross using a heterozygote for height and nose morphology. The offspring are: tall upturned snout, 40; dwarf upturned snout, 9; dwarf downturned snout, 42; tall downturned snout, 9. Calculate the recombination frequency from these data; then use your answer from problem 11 to determine the correct sequence of the three linked genes.

Between T and S, 18%; sequence of genes T-A-S

Assume that genes A and B are linked and are 50 map units apart. An animal heterozygous at both loci is crossed with one that is homozygous recessive at both loci. What percentage of the offspring will show phenotypes resulting from crossovers? If you did not know that genes A and B were linked, how would you interpret the results of this cross?

Fifty percent of the offspring would show phenotypes that resulted from crossovers. These results would be the same as those from a cross where A and B were not linked. Further crosses involving other genes on the same chromosome would reveal the linkage and map distances.

Pseudohypertrophic muscular dystrophy is an inherited disorder that causes gradual deterioration of the muscles. It is seen almost exclusively in boys born to apparently normal parents and usually results in death in the early teens. Is this disorder caused by a dominant or a recessive allele? Is it's inheritance sex linked or autosomal? How do you know? Explain why this disorder is almost never seen in girls.

Recessive Sex linked because it is only seen in boys For a girl to have the disorder, she would have to inherit recessive alleles from both parents. Considering that most people affected by this disorder die in their teens, it would be nearly impossible for her father to make it to an age where he could have children.

What pattern of inheritance would lead a geneticist to suspect that an inherited disorder of cell metabolism is due to a defective mitochondrial gene?

The disorder would always be inherited from the mother.

Women born with an extra X chromosome (XXX) are healthy and phenotypically indistinguishable from normal XX women. What is a likely explanation for this finding? How could you test this explanation?

The inactivation of two X chromosomes in XXX women would leave them with one genetically active X, as in women with the normal number of chromosomes. Microscopy should reveal two Barr bodies in XXX women.

Determine the sequence of genes along a chromosome based on the following recombination frequencies: A-B, 8 map units; A-C, 28 map units; A-D, 25 map units; B-C, 20 map units; B-D, 33 map units.

d. b and c