Cell Reproduction

• growth

• replace worn-out or damaged cells

• cells get too large to transfer materials

• reproduction (different type of division)

cell with 2 copies of each chromosome

diploid

diploid

diploid

cell with 1 copy of each chromosome

haploid

haploid

haploid

tangled mass of unwound DNA present when a cell is not dividing

condensed form of DNA present during cell division

a pair of matching chromosomes (one from mom and one from dad)

pairs of chromosomes that do not determine sex

pairs of chromosomes that determine sex

female

male

a picture of the 46 chromosomes that are arranged in pairs according to shape, size, and banding

sequence of growth and development of a cell (a cells life cycle)

division of the cytoplasm

division of a somatic (body) cells nucleus

the time between cell divisions when a cell performs its regular functions

• chromatin present

• spindle begins to form

• centrioles duplicate

growth 1, cell grows and makes proteins

synthesis, DNA (chromosomes) are replicated

growth 2, cell grows and prepares for division

• chromatin coils into visible chromosomes

• nuclear envelope and nucleus appear

• centrioles move to the poles

• sister chromatids— (doubled chromosomes) are held together by centrioles

chromosomes are pulled to the equator of the cell by spindle fibers

• chromatid pairs are pulled apart by spindle fibers

• sister chromatids become daughter chromosomes as they move toward the poles

• two new cells start to form

• nuclear envelope and nucleus reform

• chromosomes unwind into chromatin

cleavage furrows forms and the cell pinches off

cell plate (new cell wall) forms between daughter cells

type of division that forms gametes (sex cells)

• reduces the chromosomes number from diploid to haploid

• requires two sets of divisions

first stage of meiosis which separates homologous chromosomes

• chromosomes replicate

• homologous chromosomes pair up

• crossing over occurs

• homologous chromosomes are pulled apart

• two haploid cells form

exchange of genetic material between homologous chromosomes

created by crossing over and independent assortment (how the chromosomes line up)

produces 2 haploid cells

the second stage of meiosis which separates sister chromatids

produces 4 haploid gametes

• holds the chromosomes together

• where the spindle attaches

builds and controls the spindle