Ch 12-1 Flashcards
Heterozygous individuals who carry a single recessive allele for a recessively inherited disorder.
Carrier
Most common recessively inherited lethal disease in individuals of European descent
Cystic fibrosis.
Cystic fibrosis.
Loci
Combinations of alleles unique from the parental generation.
Recombinant type.
Correlating the sex of an individual organism with the presence of a specific trait.
Sex-linked trait/gene.
Regions on the Y chromosome that are homologous to the X chromosome, allowing it to act as “homologous” to the X chromosome.
Pseudoautosomal regions.
Sex-determining region of the Y chromosome.
SRY
Having a single X chromosome.
Hemizygous
Sperm donors will always pass on an X-linked recessive allele to this type of progeny.
XX progeny
Egg donors can pass on an X-linked recessive allele to these types of progeny.
Both XX and XY progeny.
Inactivated X chromosome.
Barr body.
Gene that becomes active only on the X chromosome to be inactivated.
XIST (X-inactive specific transcript).
Individuals who are heterozygous for an X-linked trait, expressing one version of the allele in half of their cells, and the alternate allele in the other half.
Mosaics
Why is it difficult to study human heredity?
a. Humans have a long generation time.
b. Humans produce relatively few offspring.
c. Breeding experiments with humans are unacceptable.
d. All of the above.
D
What is the function of the SRY gene?
a. It codes for a protein involved in the regulation of other genes involved in sex determination.
b. It produces the hormone testosterone.
c. It inactivates one of the X chromosomes in females.
d. It is responsible for the development of female secondary sex characteristics.
A
Thomas Hunt Morgan chose the fruit fly, Drosophila melanogaster, as his experimental organism because
a. Single mating results in hundreds of offspring.
b. New generation every two weeks.
c. Only four pairs of chromosomes, easily distinguishable by light microscopy.
d. Sex determined by X and Y chromosomes, as in humans.
e. All of the above.
E
Morgan concluded that the white-eye allele in fruit flies is recessive because:
a. White-eyed flies are more common in the wild.
b. All of the F1 generation from a cross between a white-eyed male and a red-eyed female had red eyes.
c. The white-eye allele is located on the Y chromosome.
d. Only male flies exhibited the white-eyed trait.
B
Morgan concluded that the white-eye allele in fruit flies must be located on the X chromosome because:
a. The white-eyed trait was always passed from father to son.
b. Only male flies exhibited the white-eyed trait in the F2 generation.
c. Female flies could not inherit the white-eyed allele.
d. The gene for eye color is linked to the gene for sex determination.
B
Which of the following statements about Y-linked genes is FALSE?
a. They are located on the Y chromosome.
b. They are only inherited by males.
c. They are always expressed in males.
d. They are relatively few in number.
C
X-linked recessive disorders are more common in males than in females because:
a. Males have two X chromosomes, while females have only one
. b. Females have two X chromosomes, while males have only one.
c. Males inherit the X chromosome from their mother, while females inherit it from their father.
d. Males only need one copy of the recessive allele to express the disorder, while females need two copies.
D
