Exam 15: The Chromosomal Basis of Inheritance

Genomic imprinting is generally due to the addition of methyl (-CH₃) groups to C nucleotides and chemical histone changes to silence a given gene. If this depends on the sex of the parent who transmits the gene, which of the following statements must be true?

Use the following figure to answer the question. The pedigree in the figure shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely ________.

Which of the following occurrences describes how recombination between linked genes comes about?

Which of the following statements correctly describes the meaning of the chromosome theory of inheritance as expressed in the early 20th century?

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their 20s. How likely is it for a woman to have this condition?

In humans, clear gender differentiation occurs not at fertilization, but after the second month of gestation. Which of the following statements describes the first event of this differentiation?

Why are males more often affected by sex-linked traits than females?

A man who is a dwarf with achondroplasia and normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. What proportion of their sons would be color blind and of normal height?

What does a recombination frequency of 50% indicate?

Which of the following phrases correctly defines what one map unit is?

A man who is a dwarf with achondroplasia and normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. How many of their daughters might be expected to be color-blind with achondroplasia?

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

Which of the following statements is generally true of aneuploidies in newborns?

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?

Which of the following is an example of monosomy in humans?

Cinnabar eye color is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F₁ males will have cinnabar eyes?

Use the following map of four genes on a chromosome to answer the question. Between which two genes would you expect the highest frequency of recombination?

A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color blind marries a color-blind male. What is the probability that this couple's first son will be color blind?

Use the following information to answer the question. In a Drosophila experiment, a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F₁s were phenotypically wild type. However, adult flies of the F₂ generation (resulting from matings of the F₁s) had the characteristics shown in the figure. How is the mutant allele for yellow body inherited?

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