BIOLOGY 1201 EXAM 3 COMPREHENSIVE
TEST PAPER WITH SOLVED QUESTIONS
◉ In humans, what determines the sex of offspring and why?
Answer: The male gamete determines sex because each male
gamete can contribute either an X or a Y chromosome.
◉ In general, the frequency with which crossing over occurs
between two linked genes depends on what?
Answer: how far apart they are on the chromosome
◉ Which of the following results in a situation in which the
chromosome number is either 2n+1 or 2n-1 ?
Answer: aneuploidy
◉ What results if a fragment of a chromosome breaks off and then
reattaches to the original chromosome at the same place but in
the reverse direction?
Answer: an inversion
◉ What phenomenon occurs when a particular allele will either
be expressed or silenced, depending on whether it is inherited
from a male or a female?
Answer: genomic imprinting
, ◉ How are human mitochondria inherited?
Answer: from the mother only
◉ Which of the following is true of an X-linked gene, but not of a Y-
linked gene?
Answer: The gene is present in both males and females.
◉ 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?
Answer: 100%
◉ Recombination between linked genes comes about for what
reason?
Answer: Crossovers between these genes result in chromosomal
exchange.
◉ 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?
Answer: The gene involved is on the X chromosome.
◉ A woman is found to have 47 chromosomes, including three X
chromosomes. Which of the following describes her expected
phenotype?
TEST PAPER WITH SOLVED QUESTIONS
◉ In humans, what determines the sex of offspring and why?
Answer: The male gamete determines sex because each male
gamete can contribute either an X or a Y chromosome.
◉ In general, the frequency with which crossing over occurs
between two linked genes depends on what?
Answer: how far apart they are on the chromosome
◉ Which of the following results in a situation in which the
chromosome number is either 2n+1 or 2n-1 ?
Answer: aneuploidy
◉ What results if a fragment of a chromosome breaks off and then
reattaches to the original chromosome at the same place but in
the reverse direction?
Answer: an inversion
◉ What phenomenon occurs when a particular allele will either
be expressed or silenced, depending on whether it is inherited
from a male or a female?
Answer: genomic imprinting
, ◉ How are human mitochondria inherited?
Answer: from the mother only
◉ Which of the following is true of an X-linked gene, but not of a Y-
linked gene?
Answer: The gene is present in both males and females.
◉ 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?
Answer: 100%
◉ Recombination between linked genes comes about for what
reason?
Answer: Crossovers between these genes result in chromosomal
exchange.
◉ 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?
Answer: The gene involved is on the X chromosome.
◉ A woman is found to have 47 chromosomes, including three X
chromosomes. Which of the following describes her expected
phenotype?
