bio 2 cell cycle and reproduction

cell cycle

most of the cell cycle is interphase, except for mitosis

phases of cell cycle

G1, S, G2, M, G0,

G1 phase

the cell makes mRNA and proteins to prepare for mitosis

S phrase

DNA is replicated

G2 phase

• cell growth occurs

• organelles are formed

• overall preparation for mitosis

M phase

mitosis and cytokinesis

DNA divides into two daughter cells

organelles divide into two daughter cells

G) phase

cell cycle exit

• the cell leaves the cell cycle it if doens’t need to divide

• a dormant phase

growth signals (CDK and Cyclin)

• CDK and cyclin bind together to create a complex

• this complex phosphorylates RB and RBP

• RBP changes shape and releases E2F

• released E2F causes cell division to continue

No CDk-cyclin complex

Blocks phosphorylation

E2F remains attached

No positive growth signal halting the cell cycle.

visual representation

if CDK and cyclin form a complex, RB is phosphorylated, E2F is released and the cell cycle progresses, If not, E2F remains bound leading to cycle arrest.

sex chromosomes

xx females

xy males

total chromosomes

23 pairs (36 total chromosomes)

one chromosome from each parent per pair

23 from mom, 23 from dad

x-linked disorders

• males express them because they only have one X chromosome.

• females can be carriers because they have two x chromosomes

• if one X has the disorbers, the other might be normal, preventing expression

y chromosome

• little genetic information

• few genes resulting in a phenotype

mitosis

pMAT: prophase, metaphase, anaphase, telophase

• ploidy is 2n throughout

prophase

• DNA condenses

• centrioles migrate to opposite poles

• microtubules from (centrioles form microtubules, two centrioles from a centrosome).

• Nuclear envelope disappears, exposing DNA

• DNA is in condensed form called chromatin

metaphase

• chromosomes line up in the middle

anaphase

• chromosomes are pulled apart

• each chromosomes is pulled in half

telophase

• chromosomes decondense

• nuclear membranes reform

• cytokinesis occurs finalizing daughter cell formation

• spindle fiber

• centrosomes, sister chromatids bound together

• interphase: normal cell state

• prophase: chromosomes condense and duplicate, attaching at the center point, spindle fibers form

• metaphase: chromosomes align in the middle. nuclear envelope disappears

• anaphase: sister chromatids are pulled apart

• telophase: nuclear envelope reforms. cytokinesis occurs forming two daughter cells

• ploidy in mitosis: 2n throughout. chromosome number remains constant even when DNA count doubles (sister chromatids attached)

meiosis

similar to mitosis but with key difference

prophase I

• chromosomes condense

• homologous chromosomes pair up (from from mom, one from dad)

metaphase 1

homologous chromosomes line up in the middle

crossing over occurs exchanging genetic material.

what is the purpose of metaphase I

to split apart homologous chromosomes, not sister chromatids

anaphase i

homologous chromosomes are split apart

telophase I

chromosomes decondense, nuclear membrane reforms (sometimes)

cells divide resulting in two haploid daughter cells of unequal size

prophase II

haploid cells prepare for division

metaphase ii

chromosomes align in the middle

anaphase ii

sister chromatids are split apart

telophase ii

• chromosomes decondense, nuclear membrane reforms

• cell divide, resulting in four haploid daughter cells

overall of meiosis vs mitosis

• mitosis: parent cell (diploid)→ daughter cells (diploid)

• meiosis: parent cell (diploid) → daughter cells (haploid)

nondisjunction

• occurs during anaphase

• chromosomes don’t split properly resulting in daughter cells with extra or missing chromosomes

• can lead to conditions like down syndrome (trisomy 21)

• aneuploidy: abnormal chromosome count

• loss of segregation: normal segregation or disjunction

what is p53

important for cell cycle checkpoint control