Exam 12: The Chromosomal Basis of Inheritance

A man who is a dwarf due to achondroplasia and has 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.Achondroplasia is autosomal dominant,and red-green color blindness is X-linked recessive. How many of the couple's daughters might be expected to be color-blind dwarfs?

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. A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type)shown in the figure below. The greatest distance among the three genes is between a and c.What does this mean?

One possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome.What is this alteration called?

When Thomas Hunt Morgan crossed his red-eyed F₁ generation flies to each other,the F₂ generation included both red- and white-eyed flies.Remarkably,all the white-eyed flies were male.What was the explanation for this result?

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

What evidence did Alfred Sturtevant use to support his conclusion that Drosophila have four pairs of chromosomes?

In cats,black fur color is caused by an X-linked allele;the other allele at this locus causes orange color.The heterozygote is tortoiseshell.What kinds of offspring would you expect from the cross of a black female and an orange male?

Which of the following results might be caused by a chromosomal translocation?

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?

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. A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type)shown in the figure below. Which of the following are the phenotypes of the parents in this cross?

Which of the following statements describes the chromosome theory of inheritance as expressed in the early twentieth century?

Which of the following statements correctly describes gene linkage?

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. A geneticist did a testcross with an organism that had been found to be heterozygous for the three recessive traits and was able to identify progeny of the phenotypic distribution (+ = wild type)shown in the figure below. In which progeny phenotypes has there been recombination between genes A and B? The parent phenotypes are 4 and 8.

Sex determination in mammals is due to the SRY gene on the Y chromosome.An abnormality of this region could allow which of the following individuals to have a male phenotype?

At what point in meiosis is a chromosome lost so that,after fertilization with a normal gamete,the result is an embryo with the chromosomal makeup of 45,X0?

One map unit is equivalent to which of the following values?

What is the reason that closely linked genes are typically inherited together?

Red-green color blindness is a sex-linked recessive trait in humans.The normal,dominant allele is symbolized with X^N,and the recessive allele is symbolized with Xⁿ.Two people with normal color vision have a color-blind son.What are the genotypes of these parents?

The figure below shows a map of four genes on a chromosome.

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