Meiosis

Meiosis purpose

to make 4 different haploid cells for sexual reproduction and genetic diversity

Haploid cell

one set of chromosomes (humans have 23)

diploid cell

two sets of chromosomes (humans have 46)

gene locus

specific location of gene on chromosome

asexual reproduction

uses mitosis to create a genetically identical offspring

asexual reproduction can be bad because

lacks genetic diversity, cannot adapt to changing environments

main steps in sexual life cycle

cell division(mitosis), gamete production(meiosis), fertilization(fusing gametes)

meiosis I vs. meiosis II

1 is reduction division, 2 is similar to mitosis

Prophase I

synapsis, crossing over occurs, chromosomes condense 

synapsis

homologous chromosomes pair up

crossing over

exchange of DNA segments between homologous chromosomes, genetic diversity increases 

Metaphase I

Homologous pairs line up at equator, independent assortment

Independant assortment

random orientation of chromosome pairs, producing genetic variation

Anaphase I

Homologous chromosomes separate and move to opposite poles

Telophase I and cytokinesis

chromosomes arrive at poles, two haploid cells form

Meiosis II

sister chromatids separate producing 4 unique haploid cells

Processes that contribute to genetic variation

crossing over, independent assortment, fertilization

Gametes

haploid reproductive cells (sperm and egg)

zygote

diploid cell formed by fusion of two haploid gametes

holds chromosomes together during crossing over

chiasma

chromosomes combinations possible in humans due to independent assortment

(2²³)

potential zygote combinations for humans when combined with fertilization

(2²³)²

Spore

fern life cycle, haploid cells develops to gametophyte

Fern life cycle

sporophyte-meiosis-spore(n)-mitosis-gametophytes-sperm and egg-fertalization-zygote(2n)