Exam 15: The Chromosomal Basis of Inheritance

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

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?

What is a syndrome?

In Drosophila melanogaster, vestigial wings are determined by a recessive allele of a gene that is linked to a gene with a recessive allele that determines black body color. T. H. Morgan crossed black-bodied, normal-winged females and gray-bodied, vestigial-winged males. The F₁ were all gray bodied, normal winged. The F₁ females were crossed to homozygous recessive males to produce testcross progeny. Morgan calculated the map distance to be 17 map units. Which of the following information is correct about the testcross progeny?

Glucose-6-phosphate dehydrogenase deficiency (G6PD)is inherited as an X-linked recessive allele in humans. A woman whose father suffered from G6PD marries a man who has the disease. What proportion of their sons would have the disease?

Glucose-6-phosphate dehydrogenase deficiency (G6PD)is inherited as an X-linked recessive allele in humans. A woman whose father suffered from G6PD marries a normal man. What proportion of their sons is expected to be G6PD?

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

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is the inheritance of this trait sex-linked or autosomal?

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

Inheritance patterns cannot always be explained by Mendel's models of inheritance. If a pair of homologous chromosomes fails to separate during meiosis I, select the choice that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n)?

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

Which of the following statements correctly describes the reason that closely linked genes are typically inherited together?

What does a recombination frequency of 50% indicate?

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

Use the following information to answer the question. 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 performed 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): Phenotypes Leaves Stems Roots Number 1 a + + 14 2 a + c 0 3 a b + 32 4 a b c 440 5 + b + 0 6 + b c 16 7 + + c 28 8 + + + 470 Total 1000 What is the greatest benefit of having used a testcross for this experiment?

A certain kind of snail can have a right-handed direction of shell coiling (DD or Dd)or left-handed coiling (dd). However, if direction of coiling is due to a protein deposited by the mother in the egg cytoplasm, then a Dd egg-producing snail and a dd sperm-producing snail will have offspring of which genotype(s)and phenotype(s)?

Sex determination in mammals is due to the SRY gene found on the Y chromosome. Which of the following situations could allow a person with an XX karyotype to develop a male phenotype?

Use the following information to answer the question. 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 performed 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): Phenotypes Leaves Stems Roots Number 1 a + + 14 2 a + c 0 3 a b + 32 4 a b c 440 5 + b + 0 6 + b c 16 7 + + c 28 8 + + + 470 Total 1000 Which of the progeny phenotypes will require recombination between genes A and B?