Section 2 Flashcards
The sequencing of human chromosomes 21 and 22 showed that
a. some regions of chromosomes do not code for proteins.
b. all of the DNA of chromosomes codes for proteins.
c. different chromosomes have the same number of genes.
d. different chromosomes contain the same number of DNA bases.
a.some regions of chromosomes do not code for proteins.
Alleles found on the same chromosomes…
are linked
The long stretches of repetitive DNA in chromosomes 21 and 22 are unstable sites
where rearrangements occur.
Most sex-linked genes are located on
the X chromosome only *
Colorblindness is more common in males than in females because
the allele for colorblindness is recessive and located on the X chromosome.
This statement is true
The mother of a colorblind boy must be colorblind.
Which of the following form(s) a Barr body?
one of the X chromosomes in a female cell
The formation of a Barr body
causes the genes on one of the X chromosomes in a female cell to be switched off.
A cat that has spots of only one color
must be a male.
The failure of chromosomes to separate during meiosis is called
nondisjunction.
Because the X chromosome contains genes that are vital for normal development, no baby has been born
without an X chromosome.
Which of the following combinations of sex chromosomes represents a female?
XX
If nondisjunction occurs during meiosis,
the chromatids do not separate.*
Nondisjunction can involve
homologous chromosomes.
Why are sex-linked traits more common in males than in females?
A recessive allele on the X chromosome will always produce the trait in a male.
Sex-linked genes are genes on
the X and Y chromosomes.
A carrier is a person who has
one recessive and one dominant allele for a trait.
What must occur for a girl to be colorblind?
Each parent must be colorblind.
Hemophilia is caused by a(n)
recessive allele on the X chromosome.
Sex-linked traits that are controlled by recessive alleles are more likely to show up in males
True
A boy who has hemophilia inherited the disorder from his
Mother
A Barr body is a turned-off ____________________ chromosome.
X
A female with the disorder _________________________ inherits only one X chromosome and has the genotype XO.
Turner’s syndrome
Nondisjunction in males can lead to the disorder called ______________________________.
Klinefelter’s
A person who has the genetic disorder called ____________________ bleeds easily.
Hemophilia
Down’s syndrome is caused by the presence of an extra ____________________.
three copies of a chromosome
A karyotype can be used to diagnose the genetic disorder called ____________________.
down syndrome
A person with Down syndrome has two copies of the 21st chromosome.
False 3
Males generally do not have Barr bodies.
true
A boy who has hemophilia inherited the disorder from his father.
False mother
A female with the disorder Kleinfelter’s syndrome inherits only one X chromosome and has the karyotype 45XO.
true
