Exam 15: The Chromosomal Basis of Inheritance

Duchenne muscular dystrophy (DMD)is caused by 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?

Which of the following is known as a Philadelphia chromosome?

Which of the following statements is true of linkage?

Calico cats are female because

Cinnabar eyes 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?

The term hemizygous refers to

Refer to the following information to answer the questions below. A man who is an achondroplastic dwarf with normal vision marries a colour-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 colour blindness is X-linked recessive. -How many of their daughters might be expected to be colour-blind dwarfs?

An abnormal number of a specific chromosome is referred to as

The phenotype most commonly observed in a natural population is the

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?

Refer to the following information to answer the questions below. A man who is an achondroplastic dwarf with normal vision marries a colour-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 colour blindness is X-linked recessive. -They have a daughter who is a dwarf with normal colour vision. What is the probability that she is heterozygous for both genes?

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

Which of the following is true of aneuploidies in general?

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?

Correns described that the inheritance of variegated colour on the leaves of certain plants was determined by the maternal parent only. What phenomenon does this describe?

Mitochondrial DNA is primarily involved in coding for proteins needed for electron transport. Therefore, in which body systems would you expect most mitochondrial gene mutations to be exhibited?

A nonreciprocal crossover causes which of the following products?

Abnormal chromosomes are frequently found in malignant tumours. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following might then occur to make the cancer worse?

What does a frequency of recombination of 50% indicate?

An inversion in a human chromosome often results in no demonstrable phenotypic effect in the individual. What else may occur?