L4 - sex determination Flashcards
What is Monoecious?
both male and female reproductive structures in the same organism (hermaphrodites), most plants, some animals
What is Dioecious?
individuals possessing only male or female reproductive structures (most animals, some plants)
What is intersex?
a term reserved for individuals of an intermediate sexual condition
Genetic sex determination is controlled by sex chromosomes and they are…
- XY/XX in mammals
- ZW/ZZ in birds
- Ratio of X chromosomes to autosomal sets (nematode worms and Drosophila)
- genetic sex determination is also controlled by the number of autosomal sets (haplodiploidy)
Non-genetic sex determination is determined by
Environmental factors (temperature, behaviours etc.)
Klinefelter syndrome
- trisomy
- aneuploidy: 47, XXY is male
- Genitalia and internal ducts are male, but testes are small, and these individuals are sterile, limited development of secondary sexual characteristics
Turner syndrome
- monosomy
- aneuploidy: 45, X is female
- short stature or amenorrhoea (lack of menstrual cycle)
- no adolescent growth (no teenage growth)
- ova degenerate in utero (infertile), limited development of secondary sexual characteristics
47, XYY is MALE
- Asymptomatic (fertile, not sterile)
- Increased growth velocity, above height average
What causes aneuploidy?
Aneuploidy is caused by non-disjunction: the failure of homologous chromosomes to separate properly in meiosis
Stages in meiosis
one DNA replication and two rounds of cell division
What is nondisjunction?
It is the failure of homologous chromosomes to separate properly during meiosis
Where is PAR (pseudoautosomal region) located on a chromosome?
at both ends and share homology with regions on the X (synapse and recombine at meiosis)
What is MSY?
Male specific region
What is SRY?
it is the sex determining region of the Y chromosome.
SRY is a gene that encodes a protein that acts as a testis determining factor (TDF). SRY is the only region of the Y required for male development.
