Bio Unit 9 - Cell Division

Mitosis used for

growth in multicellular organisms

repair and regeneration of tissues/organs

asexual reproduction in multicellular organisms (ex: spores, veg propagation)

asexual reproduction of unicellular organisms

mitosis steps

PMAT

prophase

metaphase

anaphase

telophase and cytokinesis

interphase

nuclear membrane visible; no chromosomes present

prophase

nuclear membrane disappears, chromosomes appear mitotic spindle begins to appear; centrioles on animals appear and migrate towards poles of cell

metaphase

chromosomes in single line along equater of cell; mitotic spindle formed

anaphase

sister chromatids separate; migrate to poles of cell

telophase

sister chromatids (now called individual chromosomes) clustered at poles of cell; nuclear membrane begins to reform, mitotic spindle disappearing

cytokinesis

cleavage furrow (animal) or cell plate (plant) visible; chromosomes disappearing or invisible; nuclear membrane reformed

centrioles only in..

animal mitosis

centrioles

aid in cell division

• move to opposite poles

• spindle fibers form from them

differences between plant/animal mitosis

plants do not have centrioles

plant cells have no cleavage furrow

plant cells have a cell plate

interkinesis

resting phase

right after meiosis 1 and meiosis 2

synapsis

homologous pairs “find” each other and form a tetrad

crossing-over

exchange of genetic info. between non-sister chromatids within the same tetrad

result of mitosis

1 diploid (2N) somatic cell —> 2 diploid 2N somatic cells - both cells should be identical except for point mutations

meiosis

used by multi celled organisms for

production of gametes only!

only occurs in gonadal tissues

ovaries —> ova (eggs)

testes —> sperm

synapsis and crossing-over occurs in…

prophase 1

meiosis 1: prophase 1

the nuclear membrane disappears

chromosomes appear

centrioles appear and migrate to poles

tetrads form and crossing over occurs during synapsis

meiosis 1: metaphase 1

homologous pairs line up as partners at equator

mitotic spindle fully formed

maternal/paternal chromosomes randomly situated

meiosis 1: anaphase 1

homologous pairs separate

whole chromosomes migrate to poles

random distribution of maternal/paternal chromosomes to poles ensures “independent assortment” of genetic info

meiosis 1: telophase 1

chromosomes collected at poles;

mitotic spindle disappears

nuclear membrane reappears

meiosis 1: cytokinesis 1

cleavage furrow/cell plate appears

cell divides into 2

meiosis 2: prophase 2

nuclear membrane disappears

chromosomes appear

centrioles appear and migrate to poles of cell

meiosis 2: metaphase 2

mitotic spindle fully formed

single chromosome line up at equator

centrioles at poles of cell

meiosis 2: anaphase 2

sister chromatids (now individual chromosomes) clustered at poles of cell

nuclear membrane reappears

mitotic spindle disappears

meiosis 2: cytokinesis 2

cleavage furrow/cell plate appears

cell membrane/cytoplasm splits

result of meiosis

1 diploid (2nx2) cell —> 4 haploid (1N) gametes

all 4 gametes are unique due to

point mutations

independent assortment

crossing over

independent assortment

random distribution of maternal and paternal chromosomes to gametes during meiosis

homologous pairs in tetrads line up randomly

spermatogenesis

occurs in male gonads (testes)

produces 4 haploid sperm of EQUAL SIZE

oogenesis

occurs in female gonads (ovaries)

1 large haploid cell (ootid) and 3 small polar bodies

ONLY OOTID MAY BE FERTILIZED

fertilization

union of egg and sperm

zygote

result of fertilization

full set of genetic info. (DIPLOID)

meiosis also called…

reduction division