Meiosis & Sexual Life Cycles Flashcards
what is meiosis?
-cell division that only occurs in gametes
-creates 4 haploid cells from 1 diploid cell
-each zygote contains 1 set of chromosomes from each parent
what are the two types of chromosomes?
sex chromosomes - x and y [1 set]
autosomes - everything else [22 sets]
what are homologous chromosomes?
two chromosomes that make up a “set”
-have the same traits but different alleles [ex - hair colour trait, but brown or black allele]
what is a karyotype?
a visual representation of all the chromosomes in a cell, done by “arresting” cells while they are in metaphase
what is the big picture process of meiosis?
-2 sets of PMAT division
-1st set: homologs separate, produces 2 haploid cells. 2nd set: sister chromatids separate, produces 4 haploid cells
what are the unique processes in meiosis prophase 1?
-homologs pair together and form tetrads
-genetic information is “swapped” at regions called the chiasmata
what is cohesion and the synaptonemal complex?
cohesion is a protein that holds sister chromatids together. during anaphase 2, the cohesions are released and the sister chromatids separate
-synaptonemal complex is what holds homologs together during crossing over, which occurs at the chiasmata
what are the three big processes that create genetic variety?
- independent assortment: the way one set of chromosomes align does not impact the way another set aligns, creates 2^23 possible combinations, occurs at metaphase 1
- crossing over - occurs at chiasmatas, creates even more variation
- random fertilization- only one sperm cell fertilizes one egg cell . creates 2^23 x 2^23 combinations…. a lot
why are mutations and genetic variation important?
genetic variation = material for evolution by natural selection
mutations = the original source of genetic variation. if a mutation is beneficial, it will get passed on
