Exam 15: Linkage and Chromosomes

A homozygous tomato plant with red fruit and yellow flowers was crossed with a homozygous tomato plant with golden fruit and white flowers. The F1 had red fruit and yellow flowers. F1 plants were testcrossed (crossing them to homozygous recessive individuals), and the following offspring were obtained: Red fruit and yellow flowers-41 Red fruit and white flowers-7 Golden fruit and yellow flowers-8 Golden fruit and white flowers-44 How many map units separate these genes?

In birds, sex is determined by ZW chromosome inheritance. Males are ZZ and females are ZW. Within pigeon populations there is a recessive, Z-linked allele that is lethal in embryos. What is the expected sex ratio in the offspring of a cross between a male that is heterozygous for the lethal allele and a wildtype female?

Male sex determination in mammals is in large part due to the SRY gene found on the Y chromosome. Which of the following scenarios will result in a person with an XX karyotype developing a male phenotype?

Which of the following statements regarding gene linkage is correct?

Which of the following statements correctly describes what happens to a chromosome after a nonreciprocal translocation?

German scientist Carl Correns found that the inheritance of variegated color on the leaves of certain plants was determined only by the maternal parent. Which of the following phenomena best explains this pattern of inheritance?

Which of the following statements correctly describes the chromosome theory of inheritance as it was understood in the early 20th century?

Use the following information to answer the question. A plantlike organism on the hypothetical planet Pandora has three genetic traits: leaf color, controlled by gene L; a stem texture, controlled by gene S; and root length controlled by gene R. The three genes are linked and recombine. A geneticist performed a testcross with a strain of the organism that is heterozygous for the three traits. She recorded progeny with the following phenotypic distribution: Which of the progeny phenotypes will require recombination between genes L and S?

If cell Q enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, how will this affect the gametes at the completion of meiosis?

Use the following information to answer the question. A plantlike organism on the hypothetical planet Pandora has three genetic traits: leaf color, controlled by gene L; a stem texture, controlled by gene S; and root length controlled by gene R. The three genes are linked and recombine. A geneticist performed a testcross with a strain of the organism that is heterozygous for the three traits. She recorded progeny with the following phenotypic distribution: What is the approximate distance between genes L and S?

A phenotypically normal couple seeks genetic counseling because the man's karyotype showed that his chromosomes had a reciprocal translocation between chromosomes 4 and 12. Because the translocation is reciprocal there was no genetic information lost and he is healthy; however, he and his wife want to know the probability that his sperm cells will be abnormal. Which fraction of his sperm cells is predicted to carry at least one chromosome with a translocation?

In humans, clear sex differentiation does not occur at fertilization. It becomes evident after the second month of gestation. Which of the following statements describes the first event of sex differentiation in human embryos?

Which of the following correctly describes a Philadelphia chromosome?

Males are more often affected by X-linked traits than are females because ________.

Which of the following individuals will inherit an X-linked allele from a male parent who carries the allele?

A patient has 47 chromosomes, including three X chromosomes. Which of the following statements describes her expected phenotype?

Use the diagram of six loci on a chromosome to answer the question. Locus Y is six map units from Locus X. When attempting to map the location of Gene Q, relative to Locus Y and Locus Y, two testcrosses were performed and the following data collected. Number of offspring These data narrow the possible location of Gene Q to which of the following choices?

In cats, an X-linked locus is responsible for fur color. There are two known alleles at this locus. One results in black fur color; the other results in orange color. A heterozygote animal has patches of orange and black fur (tortoiseshell). Which of the following outcomes represents all of the possible offspring from the cross provided. Assume all cats have two sex chromosomes.

When Thomas Hunt Morgan crossed red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies, but all the white-eyed flies were male. Which of these best explains Morgan's result?

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients' muscles weaken over time because they have a lack or decreased levels of dystrophin, a muscle protein. Which of the following correctly predicts the probability of muscular dystrophy in female children?