Chapter 12 The Cell Cycle

what are somatic cells and gametes?

somatic cells are nonresponsive body cells with two sets of chromosomes. gametes are reproductive cells (sperm&eggs) with half as many chromosomes

what are chromatin genome, and cytokinesis?

chromatin is DNA plus protein, which condenses during cell division. the genome is all the DNA in a cell. cytokinesis is the divsion of teh cytoplasm

what are sister chromatids and the centromere?

sister chromatids are two attached identical copies of a chromosome, the centromere is the narrow

what are homologous chromosomes?

chromosomes that carry the same set of genes, one from mom and one from dad, they are simular but not identical copies

how do a chromosome and a chromatid differ?

a chromosome exists throughout the cells life and carries DNA. chromatids appear only when a cell is dividing, and sister chromatids are exact copies of each other.

why is cell division important?

it lets signal celled organisms reproduced, drives embryonic development, renews and repairs tissue, and passes identical genetic material to daughter cells.

what are the 3 types of cell division and who uses them?

binary fission is used by single celled prokaryotes.mitosis is used by multicellular eukaryotes for body cells. meiosis is used by multicellular eukaryotes to make gametes.

binary fission

division in bacteria and archaea. the cromosomes replicates and the copies move apart then the plasma membrane pinches inward and splits

what happens in mitosis?

cells grow and copies its DNA, the copies seperate and the cytoplasm splits. making 2 identical cells

how do mitosis and meosis compare

mitosis happens in somatic cells for growth and repair, and yeilds 2 identical daughter cells with the same chromosome number. meosis makes gametes for sexyal reproduction and yeilds 4 non identical cells with half the chromosome number

what are the 2 main parts of a cell

interphase (cell growth & chromosome copying) and mitotic phase ( mitosis plus cytokinesis)

what happens in G1,S, and G2?

G1 (first gap) is growth and normal metabolic activity . S (synthesis) when DNA is copied. G2 (second gap) is more growth and preparation for division. the cell grows in all 3, but chromosomes are duplicated only in S.

what are the 5 stages of mitosis?

prophase, pro metaphase, metaphase, anaphase, and telophase followed by cytokinesis

what happens in prophase?

chromosomes condense (each is 2 sister chromatids), the early mitotic spindle forms, and the centrosomes with their asters move toward opposite ends of the cell

what happens in prometaphase?

the nuclear envolpe fragments , and kinetochore microtubules attach to the kinetochores on each chromosome. by the end the two centrosomes are at opposite poles

what happens in metaphase?

all chromosomes line up at the metaphase plate, and imaginary plane midway between the 2 spindle poles

what happens in anaphase

sister chromatids separate and are pulled toward opposite ends of the cell. kinetochore microtubules shorten and non kinetochore microtubules push against eachother and elongate the cell.

what happens in telophase and cytokinese?

two new nuclei form, nuclear envelopes and nucleoli reappear, chromosomes begin to decondense, and the cytoplasm divides into 2 daughter cells

mitotic spindle

the spindle is a microtubule structure that controls chromosome movement in mitosis

kinetochore

a protein complex at the centromere of each sister chromatid. kinetochore microtubules attach here, and motor proteins (walk) the chromosome along them in anaphase as the microtubules shorten (depolymerize)

how do cytokinesis differ in animal and plant cells?

aniaml cells pinch in a cleavage furrow using contractile ring of microfilaments. plant cells build a cell plate from vesicles, which becomes a new cell wall

what is the cell cycle control system and whats the point?

the control system is set of molecular signals that directs the sequence of cell cycle events. chechpoints are points where the cycle stops ultil a go-ahead signal arrives. they respond to both internal & external signals.

what are the 3 internal checkpoints and what does each ask?

G1 asks whether cell divison is nessasary, whether growth factors are present , whether nutrients are available. G2 asks if DNA was replicated correctly and if the cell is large enough. the metaphase (M) checkpoint asks whether all chromosomes are attached to microtubules

what is the G1 checkpoint and what is G0?

for many cells G1 is the most important checkpoint. with a go-ahead signal, the cell usually completes S, G2, and M and divides. without one, it exits the cycle into a non dividing state called G0

what are growth factors?

external chemical signals released by some cells that simulate other cells to divide

what is density dependent inhibition?

crowded cells stop dividing. in a culture dish, cells divide until they form a single layer, fill any gap, and then stop

what is a anchorage dependence?

most animal cells must be attached to a surface (substratum) to divide

how do cancer cells escape cell cycle controls?

they ignore normal regulatory signals and keep dividing even when growth factors are depleted. they may make their own growth factor, pass a growth signal without the factor or have an abnormal control system. they show either density- dependent inhabition nor anchorage dependence and most have lost the ability to repair DNA damage

what is metastasis?

a spread of cancer cells from the original tumor