Bio: Mitosis and Meiosis

cell cycle description

interphase and cell division

mitosis description

the process by which eukaryotic somatic cells replicate; asexual reproduction of identical daughter cells/cloning

cells that undergo mitosis

somatic cells

importance of a constant number of chromosomes

a change can cause problems with growth, development, and function of the body's systems

zygote

a diploid cell that is the result of

types of cells that undergo meiosis

germ(sex) cells

Proto Oncogene

pre-cancerous, before it is mutated

what restarts the cell cycle

cyclins (proto oncogenes)

checkpoints

1. cell growth check point


1. at the end of the G1 phase
2. checks if the cell is big enough and has made the right proteins for the synthesis phase
2. DNA synthesis checkpoint


1. during S phase
2. checks if DNA has been replicated correctly
3. Mitosis checkpoint


1. during mitosis
2. checks if mitosis is complete

G1 phase

cell growth

S phase

DNA replication

G2 phase

preparation for mitosis

cytokenesis

the division of the cytoplasm during telophase; must happen after anaphase

prophase

chromosomes become visible as paired chromatids and the nuclear envelope disappears. The first prophase of meiosis includes the reduction division and crossing over.

anaphase

chromosomes move away from one another to opposite poles of the spindle

metaphase

chromosomes align at the metaphase plate; chromosomes become attached to the spindle fibers

telophase

chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed

interphase

the resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis

homologous chromosomes

pairs of alike chromosomes (same genes/gene positions, same length)

synapsis

pairing of homologous chromosomes

tetrad

the group of four sister chromatids within the homologous chromosomes

bivalent

group of two homologous chromosomes

crossing over (recombination)

homologous chromosomes intertwine and exchange genes

spermatogenesis

sperm formation

oogenesis

egg formation

Meiosis I

number of cells is doubled, crossing over occurs, each new cell has half the number of chromosomes as the first cell

Meiosis II

the number of chromosomes in each cell remains the same, four cells, chromosomes separate into chromatids

nondisjunction

an error during chromosome separations

gametes

sperm and egg cell

zygote

fertilized egg

diploid

full number of chromosomes for a species (2n)

haploid

half of the full set of chromosomes (n)

polar bodies

mall cellular byproduct of the meiotic division of an oocyte; serve to eliminate one half of the diploid chromosome set produced by meiotic division in the egg, leaving behind a haploid cell

p27

a protein that binds to cyclin and CkK blocking entry into S phase

breast cancer prognosis is determined by low p27 levels

p53

a protein that blocks the cell cycle if DNA is damaged


1. levels are increased in damaged cells alowing for DNA to be repaired
2. a mutation in p53 can lead to cancer

CdK (cycliln dependent kinase)

adds phosphate to a protein; causes the cell to move from G1 to S or G2 to M