Sexual Reproduction and Meiosis

asexual reproduction

single individual passes on all of its genes to progeny (genetically identical)

sexual reproduction

2 parents —> progeny inherit 1/2 genes from each (genetically unique)

G1 phase

gap (growth phase)

G0 phase

cell cycle exit

S phase

synthesis

G2 phase

gap (growth phase)

M phase

mitosis

cytokinesis

division of cytoplasm

homologous chromosomes

1 maternal, 1 paternal

monad

1 chromosome + 1 DNA molecule

dyad

1 chromosome + 2 DNA molecules

sister chromatids

one of the two identical copies of a chromosome before divison

meiosis

cell division that produces haploid gametes

gametes

sex cells —> sperm _

meiosis I

separate homologous chromosomes (also known as reductive division)

meiosis II

sister chromatids separate into 4 new cells

synapsis

homologous chromosomes pair up with each other

bivalent / tetrad

when chromosomes begin to cross over with one another

crossing over

each chromosome receives a small piece of the other on the distal end

chiasmata

the finished product of chromosomes crossing over

meiotic spindle

strings that attach to the chromosomes and pull them to opposite poles

cohesion

holds sister chromatids together

anaphase I

homologous chromosomes are separated

metaphase I

homologous chromosomes line up on metaphase plate

telophase I

cell divides to form 2 cells and nuclei reform

prophase I

chromosomes condense and the nuclear envelope disintegrates

separase

cleaves cohesion proteins and allows chromatids to separate

shugoshin

protects cohesins from being cleaved in meiosis I (is disintegrated in meiosis II)

interkinesis

brief resting period between meiosis I and meiosis II

prophase II

chromosomes condense and nuclear envelope disintegrates

metaphase II

chromosomes line up along middle of equatorial plane

anaphase II

sister chromatids separate and are pulled to the poles

telophase II

cells divide into 4 haploid gametes

recombination

two chromatids from a divalent pair swap portions of DNA

independant assortment

when chromosomes are lined up it is random therefor the assortment of is random, as will be the gametes

gametogenesis

makes gametes

fertilization

fusion of the sperm and egg to form a diploid

zygote

a fused sperm and egg

spermatogenesis

makes sperm

spermatogonium

the starting cell, can produce more spermatogonia by mitosis

primary spermocyte

enters meiosis I

secondary spermocyte

after meiosis I

spermatids

4 products of spermatogenesis, which develop into sperm cells

mature sperm cell

haploid male reproduction cell

oogenesis

generation of egg cells (occurs in ovaries)

oogonium

starting cell

primary oocyte

enters meiosis I, occurs in utero and remains arrested in prophase I until puberty

secondary oocyte

product of cell division

ovum

mature female reproductive cell