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.
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
Which of the following is an example of an X-linked recessive disorder?
a. Huntington’s disease
b. Cystic fibrosis
c. Hemophilia
d. Down syndrome
C
Which of the following statements about X chromosome inactivation is FALSE?
a. It occurs randomly in each female cell.
b. It inactivates the paternal X chromosome in all cells.
c. It results in the formation of a Barr body.
d. It ensures that males and females have the same effective dose of X-linked genes.
B
A female who is heterozygous for an X-linked recessive disorder is called a:
a. Carrier
b. Mosaic
c. Hemizygote
d. Mutant
A
How many genes are on the Y chromosome?
a. 25
b. 78
c. 1100
d. 3500
B
When do anatomical signs of sex emerge in a human embryo?
a. Conception
b. 1 month
c. 2 months
d. 3 months
C
What is an example of a Y-linked disorder?
a. Color blindness
b. Hemophilia
c. Reduced functional gamete (sperm) production
d. Duchenne muscular dystrophy
C
During which phase of meiosis do chromosomes segregate?
a. Prophase I
b. Metaphase I
c. Anaphase I
d. Telophase I
C
A person with XX chromosomes will create:
a. Sperm
b. Eggs
c. Both sperm and eggs
d. Neither sperm nor eggs.
B
T/f
The white-eyed allele in fruit flies is dominant.
F. The white-eyed allele in fruit flies is recessive.
T/f
The Y chromosome determines sex in humans.
T
T/f
Females can be carriers of X-linked recessive disorders.
T
T/ f
All genes on the X chromosome are involved in sex determination.
F
The X chromosome contains approximately 1100 genes, many of which are not involved in sex determination.
T/f
X chromosome inactivation occurs randomly and independently in each embryonic cell.
T
T/f
Barr body is a highly condensed Y chromosome
F.
Barr body is a highly condensed X chromosome.
T/f
X-linked recessive disorders are never seen in females.
F
X-linked recessive disorders can be seen in females if they inherit two copies of the recessive allele.
T/f
Chromosomes undergo segregation and independent assortment.
T
T/f
The pattern of inheritance for sex-linked traits is dependent on who starts with the mutation (maternal vs. paternal).
T
T/f
In humans, individuals with XY chromosomes create eggs.
F
In humans, individuals with XX chromosomes create eggs.
What is duchenne muscular dystrophy and give a sign
weakening of muscles
• Loss of coordination due to absence of muscle protein [dystrophin]
What is hemophilia
absence of 1 or more proteins involved blood clotting
What term is this
“is a way for the cell to “turn off” one X chromosome so that females don’t have double the X chromosome activity compared to males (who have only one X chromosome)”
Barr body
Pseudoautosomal
small regions on X & Y sex xsome that can pair up like non sex xsomes
• These regions allow X & Y xsome to exchange genes
4 reasons why thomas morgan used a fly
new gen every 2 weeks
• single mating results lots of offspring
• Only 4 pairs of xsome can easily be seen by light microscopy
• Sex determined by X & Y xsomes
Morgans 2 contribution
1) Showed unique inheritance patterns for sex-linked traits
2) pattern of inheritance is dependent on who starts mutation [maternal vs paternal]
Recombinant type meaning
create combinations of traits unique from parental generation
• Mixing of diff traits bc they appear on diff xsome
Mutant phenotypes meaning
Traits that appear different from “normal” ones
• changes in original wild-type gene sequence
What does sry stand for
Sex determining region of Y xsome
Absence of SRY means
no Y xsome (XX female), embryo develop as female
Presence of SRY means
has Y xsome, this gene leads to development of male traits [testes]
What does it mean when XX indiv are mosaic and give an example
Heterozygous XX indiv will express one version of allele in half of their cells, alternate allele in other half
Ex: XX heterozygous for mutation in sweat gland development will have patches of normal skin + patches which lack sweat gland
