Sex Determination Flashcards
How is the
Sex determination of birds, mammals and some insects
determined
by presence of sex chromosomes
SRY gene
it is on the Y chromosome and it determines development of malew characteristics
WHy are
Sex linked traits always more common than males
Males only need to inherit one affected allele while females need to inherit two
X inactivation in
Homogametic females(XX)
one of the two chromosomes present in each cell is randomly inactivated at early stage in development
What does
X chromosome inactivation prevent
A double dose of gene products which could be harmful to cells
Carriers are less likely to be affected by harmful mutations on these
X chromosomes
What are hermaphrodites
Individuals that have functioning male and female reproductive organs
eg snails slugs and most plants
They produce both gametes
Benefit of hermaphroditism
if chance of encountering a partner is uncommon,the individual organism has no requiremnt for the partners sex
environmental sex determination in reptiles
Controlled by environmental temp of egg incubation, rather than genetic factors
Sex change in individuals of some species as a result of…
- size
- competetion
- parasitic infection
- temperature
