Exam 12: The Chromosomal Basis of Inheritance

If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, what will be the result at the completion of meiosis?

What is the source of the extra chromosome 21 in an individual with Down syndrome?

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?

A nonreciprocal crossover causes which of the following products?

Which of the following is known as a Philadelphia chromosome?

How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?

In which progeny phenotypes has there been recombination between genes A and B?

What is one map unit equivalent to?

What proportion of their sons would be color-blind and of normal height?

A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following describes her expected phenotype?

Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila in which of these ways?

Down syndrome has a frequency in the U.S. population of ~1/700 live births. In which of the following groups would you expect this frequency to be significantly higher?

Use the following information to answer the questions below. A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and hollow roots due to an allele (c) of gene C. The three genes are linked and recombine as follows: A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and she was able to identify progeny of the following phenotypic distribution (+ = wild type): Figure 12.3 -Which of the following are the phenotypes of the parents in this cross?

SRY is best described in which of the following ways?

All female mammals have one active X chromosome per cell instead of two. What causes this?

Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?

In humans, clear gender differentiation occurs not at fertilization, but after the second month of gestation. What is the first event of this differentiation?

Why does recombination between linked genes continue to occur?

Refer to the following information to answer the questions below. A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was 6 feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive. -How many of their daughters might be expected to be color-blind dwarfs?

Males are more often affected by sex-linked traits than females because