5.2 Meiosis and Genetic Diversity

crossing over results in..

recombinant chromatids - chromosomes carrying new combos of maternal/paternal alleles

recombinant chromatids and genetic diversity

many potential combos and cross over events = more unique genetic combos

independent assortment

tetrads align independently > random distribution of material/paternal chromosomes

n pairs (haploid) + independent assortment

2n (diploid) number of combinations

what determines the different combos on each metaphase plate?

which side the maternal or paternal chromosomes end up on

random fertilization

any sperm (multiple) can fuse with any egg

random fertilization and genetic diversity

gametes individually distinct = many types of possible genotypes in zygotes

are full siblings genetically distinct?

yes - each has a different combo of alleles (genetic and phenotype variation)

nondisjunction

failure of chromosomes/sister chromatids to separate properly

nondisjunction and fertilization

fertilizing with affected gametes = zygotes with aneuploidy (abnormal chromosome number)

abnormal number of chromosomes examples (2)

extra chromosomes (n+1), lack of chromosomes (n-1)

errors in mitosis - plant and human effects

plants - vigor/growth animals - sterility and disorders

can errors occur in mitosis?

yes - nondisjunction in embryogenesis = mosaicism (different tissues have different chromosome compositions)

meiosis as an engine of evolution

generations shuffle existing alleles > combos acted upon by natural forces > population adaptation

consequences of loss of meiosis (2)

slow evolutionary change, compromised survival of populations