Sex Determination Flashcards
What determines the sex of birds, mammals and some insects?
Sex Chromosomes
What determines the development of male Characteristics?
The SRY gene on the Y chromosome
What do Heterogametic (XY) males lack?
Most of the corresponding homologous alleles on the shorter (Y) chromosome
Males lacking corresponding homologous alleles can result in?
Can result in sex-linked patterns of inheritance as seen with carrier females (X^B X^b) and affected males (X^b Y)
What happens to homogametic females (XX) one of the two X chromosomes present in each cell?
One is randomly activated at an early stage of development
What is X chromosome inactivation?
Is a process by which most of one X chromosome is inactivated.
What does the inactivation of the X chromosome prevent?
X chromosome prevents a double does of gene products, which could be harmful to cells.
What is the benefit to carriers of the inactivation of the X chromosome?
They are less likely to be affected by any deleterious mutations on these X chromosomes.
As the X chromosome is inactivated in each cell is random what does this mean for a working copy?
Half of cells in any tissue will have a working copy of the gene in question
For some species, what genetic factors determine sec and sex ratio
Environmental
What is environmental sex determination?
In reptiles is controlled by environmental temperature of egg incubation
What can cause sex change within some individuals?
Size, competition or parasitic infection.
What can adjust the sex ratio?
The sex ration of offspring can be adjusted in response to resource availability.
