2.3c - Sex Determination Flashcards
The sex of birds, mammals and some insects is determined by…
the presence of sex chromosomes
In most mammals the SRY gene on the Y chromosome determines…
development of male characteristics
Heterogametic (XY) males lack…
most of the corresponding homologous alleles on the shorter (Y) chromosome
Lacking most of the corresponding homologous alleles on the shorter (Y) chromosome can result in…
sex-linked patterns of inheritance as seen with carrier females (X^BX^b) and affected males (X^bY)
In homogametic females (XX) one of the two X chromosomes present in each cell is…
randomly inactivated at an early stage of development
X chromosome inactivation is..
a process by which most of one X chromosome is inactivated
X chromosome inactivation prevents…
a double dose of gene products, which could be harmful to cells
Carriers are less likely to be affected by…
any deleterious mutations on inactivated X chromosomes
As the X chromosome is random…
half of the cells in any tissue will have a working copy of the gene in question
Hermaphrodites are…
species that have functioning male and female reproductive organs in each individual
Hermaphrodites produce…
both male and female gametes and usually have a partner with which to exchange gametes
The benefit to the individual hermaphrodite is…
that if the chance of encountering a partner is an uncommon event, there is no requirement for that partner to be of the opposite sex
Rather than genetic factors, for other species…
genetic factors determine sex and sex ratio
Environmental sex determination in reptiles is controlled by…
environmental temperature of egg incubation
Sex can change within some species as a result of…
size, competition, parasitic infection or temperature
In some species the sex ratio of offspring can be adjusted in…
response to resource availability
