Signalling 2 - Signalling in Sex Determination Flashcards
What are the gonads?
- ovaries
- testes
When is the sex of mammals determined?
at fertilisation
What is the process of sex determination in mammals?
- the genetic signal instructing gonad formation
- once the gonads are determined they control the secondary sex characteristics
- Sry is a TF only expressed on the Y chromosome
- Sry will determine the gonads
What is Sry?
sex determining region Y chromosome (TF)
What is the wolffian duct?
precursor of vas derferens - male
What is the Mullein duct?
- precursor of the oviduct - female
What is the effect of Sry?
- causes gonads to become testes and not ovaries
- male structures persist and female structures disappear
How does testosterone signalling work?
- hydrophobic steroid hormone
- released into the blood
- crosses the membrane and binds to receptor proteins to regulate gene expression in target cells
How do the testes determine secondary sex characteristics?
- secrete male hormones which act on distant target cells
- Mullian-inhibiting substance - inhibits the Mullein duct
- testosterone - signals to wolffish dust to develop into vas deferens which will carry sperm
- testosterone - signals secondary male sex character
How does female sex determination happen?
- no Sry signal
- gonads will become ovaries
- female structures persist
- male structures disappear
- no Mullarian inhibiting substance so oviduct develops
- no testosterone so vas deferans dont develop
- ovaries secrete female hormones which instruct female phenotype
What is the default sex?
female
what are androgens?
male characteristic determining hormones
what is complete androgen insensitivity syndrome (CAIS)?
- some XY people dont have functional receptors fro androgens
- they have internal testes but develop as females
What is the gametes of a female chicken?
ZW
What is the gametes of a male chicken?
ZZ
What is a gynandromorph chicken?
- has both male and female features
Female side
- small wattle
- brown plumage
- no spur
Male side
- large wattle
- gold plumage
- spur
- it is a picture of ZZ and ZW cells
Is endocrine signalling enough to determine secondary sex characteristics in chickens?
No - as they are both exposed to the same hormones
What is cell autonomous sex determination?
sexual fate is determined by the genetics of the cell - birds ect
what is a mosaic?
- genetic changes in cell lineage derived from a single zygote
What is a chimera?
fusion of genetically distinct embryos
What is non-cell autonomous sex determination?
sex is determined based on signals from other cells, rather then directly from their genotype - mammals
How does alligator sex determination happen?
- incubation temp determines sex
- warm - 34 degC - males
- cool - <30 degC - females
- also happens in fish
