cell reproduction

asexual reproduction

offspring are identical to the original cell or organism

inheritance of all genes from one parent

no egg or sperm involed

sexual reproduction

offspring are similar to parents, but show variations in traits

involves inheritance of unique sets of genes from two parents

half and half genetic material

binary fission

prokaryotes reproduce by:

asexual:no organelles

binary fission—>?—>?

chromatin

DNA wound around proteins called histones (exists most of the time in a cell’s life)

growth, cell replacement, and asexual reproduction (ex. yeast)

why do we do mitosis

cell cycle

ordered sequence of events for cell division

interphase

growth (duplication of cell contents)

G1

growth, increase in cytoplasm (longest phase)

S

duplication of chromosomes; 46—>92 chromatids

G2

growth, preparation for division, organelles copied

interphase and mitotic phase

tw parts of cell cycle

mitosis

division of nucleus

cytokinesis

division of cytoplasm

prophase

-in the cytoplasm: microtubules emerge from centrosomes (centrioles), forming the spindle fibers in the nucleus

-in the nucleus: chromosomes coil, become compact, and are visible; nucleolus disappears

prometaphase

spindle microtubules span across the cell

spindles attach the centromeres of sister chromatids

spindles move chromosomes to the center of the cell

the nuclear envelope disappears

metaphase

spindle is fully formed across the cell

chromosomes align at the cell equator

sister chromatids are facing the opposite poles of the spindle

anaphase

sister chromatids separate at the centromeres

daughter chromosomes (each sister) are moved to opposite poles of the cell

the cell elongates

anaphase ends when chromosomes reach the 2 poles of the cell

telophase

the cell continues to elongate

the nuclear envelope forms around groups of chromosomes at each pole, establishing daughter nuclei

the chromosomes uncoils into chromatin

nucleoli reappear

the spindle disappears

cytoplasm starts to pinch in

cytokinesis

cytoplasm is divided into separate daughter cells

animal cells form a cleavage furrow (membranes pinches in)

plant cells form a cell plate (cannot pinch in due to cell wall)

homologous chromosomes

somatic cells have pairs of _____

one of each pair comes from each parent

length, centromere position, and gene locations

homologous chromosomes match in:

locus (loci)

position of a gene

karyotype

picture of chromosomes arranged; largest to smallest in pairs; sex chromosome are last

crossing over

____can result in genetic variations in chromosomes

can happen at multiple locations

meiosis

____converts diploid nuclei to haploid nuclei

diploid cells

have two homologous sets of chromosomes

haploid cells

have one set of chromosomes

fertilization

union of sperm and egg

gamete

sperm and egg

preceded

meiosis is _____ by interphase

prophase I

chromosomes coil and become compact

homologous chromosomes come together as pairs

each pair, with four chromatids, is called a tetrad

nonsister chromatids exchange genetic material by crossing over

metaphase I

tetrads align at the cell equator

anaphase I

homologous pairs separate and move toward opposite poles of the cell

telophase I

duplicated chromosomes have reached the poles

a nuclear envelope forms around chromosomes in some species

each nucleus has the haploid number of chromosomes (23 different chromosomes, 23 copies)

reduction division

meiosis I is often called____

prophase II

chromosomes coil and become compact

metaphase II

duplicated chromosomes align at the cell equator

anaphase II

sister chromatids separate and chromosomes move toward opposite poles

telophase II

chromosomes have reached the poles of the cell

a nuclear envelope forms around each set of chromosomes

with cytokinesis, four haploid cells are produced