Gametogenesis Short Flashcards
describe gametogenesis
the production of sperm and eggs
what are the primordial germ cells
precursor to the gametes (sperm, egg)
they multiply and migrate to genital ridge (precursor to primitive gonad)
what dictates if testes will develop
the SRY gene on the Y chromosome
what is the production of androgens from foetal testes essential for
the production of sperm & the internal and external genitalia
what is undergone to form gametes by what
primordial germ cells (diploid) undergo meiosis to form gametes (haploid)
reduction number chromosomes from 46 to 23
also see recombination => genetic diversity
when does spermatogenesis occur
starts at puberty & continues to end of life
but see decline in sperm quality
when does oogenesis occur
starts before birth. fixed number of oocytes at birth
oocytes suspended at prophase1 until puberty where meisosi (oogenesis) resumes with ovulation.
continues until time where most follicles exhausted around menopause at approx age 50
what happens to the fixed number of oocytes at birth
over 99% of oocytes do not ovulate and lost through atresia
others do ovulate but are not fertilised
some are fertilised
what is epigenetics
non-DNA changes in gene expression
what can also alter gene expression (through affecting epigenetics)
- environmental influences
- intergenerational effect in utero on oocytes, sperm, embryos
- maternal malnutrition
what do we see during gametogenesis and embryo development in epigenetic occurrences
demethylation and reestablished methylation patterns including imprinting
- factors that influence gene expression can impact this process which is also when oocytes being formed in foetal gonad and sperm and developing embryo and foetus
what can epigenetic changes influence
risk of major diseases in later life including hypertension, heart disease, obesity
