Exam 15: The Chromosomal Basis of Inheritance

A phenotypically normal prospective couple seeks genetic counselling because the man knows that he has a translocation of a portion of his chromosome 4, which has been exchanged with a portion of his chromosome 12. Although his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm?

Which of the following statements regarding gene linkage is correct?

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?

Which of the following correctly describes a Philadelphia chromosome?

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?

A man who is a dwarf with achondroplasia and normal vision marries a colour-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 colour blindness is X-linked recessive. How many of their daughters might be expected to be colour-blind with achondroplasia?

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?

In cats, black fur colour is determined by an X-linked allele; the other allele at this locus determines orange colour. 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 statements is generally true of aneuploidies in newborns?

Between which two genes would you expect the highest frequency of recombination?

During meiosis, a defect occurs in a cell that results in the failure of spindle microtubules binding at the kinetochores. Which of the following statements describes the most likely result of such a defect?

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

Mitochondrial DNA is primarily involved in coding for proteins needed for protein complexes of the electron transport chain and ATP synthase. Therefore, mutations in mitochondrial genes would most affect which of the following processes?

A man who is a dwarf with achondroplasia and normal vision marries a colour-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 colour blindness is X-linked recessive. What proportion of their sons would be colour blind and of normal height?

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

A plant-like 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?

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 colour. Thomas H Morgan (1907) crossed black-bodied, normal-winged females and grey-bodied, vestigial-winged males. The F1 were all grey 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?

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