SEX LINKAGE AND DNA & CHROMOSOME STRUCTURE Flashcards
The term “sex” refers to an organism’s sexual _____.
phenotype
Y-linked markers are
DNA sequences on the Y chromosome that vary among individual males.
In mammals, each inactivated X chromosome forms a darkly staining body known as a _____ body.
barr
Individuals with Turner syndrome most often have which sex chromosomes?
XO
A woman who is heterozygous for the sex-linked condition of red–green color blindness marries a man with normal vision. Which of these would you not expect to observe among their possible children?
a son with normal vision and a daughter who is color blind
Within each female cell, what is true of X chromosomes that are inactivated?
The X chromosome that is inactivated is random.
In XX–XO sex determination, males have which sex chromosomes?
a single X chromosome
Studies of rare white-eyed males in Drosophila crosses by _____ demonstrated that the gene for white eyes is on the X chromosome and confirmed the chromosome theory of inheritance.
Bridges
Assume that a mutation occurs in the Xist gene of a XY male that makes the gene inactive. What would you expect would be the phenotypic consequences of this mutation for the male?
He would probably have no phenotypic consequences.
What is the sexual phenotype for the X:A ratio equal to 1.3?
metafemale
How is dosage compensation achieved in fruit flies?
doubling gene activity on the X chromosome of males but not of females
In which sex-determining system is the female the heterogametic sex?
ZZ–ZW
What does functional hemizygosity mean?
The cells in an individual female are not identical with respect to the expression of the genes on the X chromosome.
A eukaryotic diploid cell from an organism with the XX–XO sex determination system has two pairs of autosomes and one X chromosome. One pair of autosomes has a heterozygous locus with alleles A and a. The other pair of autosomes has a heterozygous locus with alleles B and b. What is the probability of a gamete from this individual having this genotype: alleles a and b, without chromosome X?
1/8
