understanding meiosis topic 3 Flashcards
(11 cards)
meiosis happens in order to make gametes
gametes are egg and sperm cells
meiosis produced cells are haploid
they are haploid so that have a full set go genetic material when fertilisation occurs
meiosis makes four genetically different cells 3 of which are discarded
haploid cells have 23 chromosomes where and diploid have 46 chromosomes ?
during prophase one of meiosis- paternal and maternal chromosomes join to form homologous chromosomes.
next these homologous chromosomes replicate to form sister chromatids
(sister chromatids are newly replicated chromosomes)
( non sister chromatids - original chromosomes)
next crossing over takes place at chiasmata to form a bivalent aiding genetic diversity
gene linkage is identifies as genes that are close together and haven’t been separated during crossing over are likely to be inherited together
Aswell as this histone modification takes place to accustom new chromosomes - hastens are DNA wrapped around proteins that aids the condensing of chromatin which is just DNA and other proteins (these substances make up chromosomes)
nuclear membrane also breaks down
next in metaphase 1 homologous pairs line up at equator of the cell
independent assortment takes place which is when homologous chromosome pairs (still 4 chromatids) line up in random formation contributing to genetic variation
next in anaphase 1 spindle fibres from centrioles attach to the chromosomes and pull them apart to each poll of the cell reducing chromosome number by half
next telophase one happens which is cytogenesis
what is Chromsomes made up of
chromatin
what is a histone proteins
ada wrapped around a protein
what is chromatin
dna and proteins
what is the purpose of histones
condensing chromatin into a chromosome histone modification takes place to be Abel to aid condensing on new chromosome ( chromosome structure)
