Cell Division DAT CH 5

Cell theory

all cells arise from preexisting cells through cell division

Genome

all the DNA in a cell

Chromosomes

individual molecules of DNA that each contain a portion of the entire genome

Homologous Chromosome Pairs

pairs of chromosomes that contain the same genes in the same order, with one inherited from each parent

Sister Chromatids

Identical, attached copes of a single chromosome that form dyads

Dyads

replicated chromosomes containing two sister chromatids to look like an x

Centromeres

regions of DNA that connect sister chromatids into a dyad

Kinetochore

proteins on the side of centromeres that help microtubules pull sister chromatids apart during cell division

Karyokinesis

division of the nucleus

cytokinesis

physical division of the cytoplasm and cell membrane

parent cell

original cell that undergoes cell division to produce two daughter cells

Ploidy

describes the number of chromosome sets found in the body (humans are diploid with haploid gametes)

Sex chromosomes

one pair in the human body, they determine sex

autosomes

22 pairs in the human body, they are nonsex chromosomes

gametes

haploid cells (sperm and egg)

germ cells

diploid cells that divide and increase by mitosis and differentiate into gametocytes

gametocytes

eukaryotic differentiated germ cells that can undergo meiosis to produce gametes

somatic cells

all body cells excluding the gametes, diploid in humans

The cell cycle

divided into interphase and M phase

Interphase

Precedes mitosis and meiosis, 90% of the cell cycle G1, G0, S, and G2

M Phase

karyokinesis and cytokinesis occur in this part of the cell cycle

G0

Cell carry out normal functions but halt in the cell cycle, cells that do not divide are stuck here

G1

cells grow in preparation for cell division, checks for favorable conditions. If favorable will continue to S phase, if unfavorable will enter G 0 phase

S Phase (synthesis)

cell replicates its genome here and moves to G2 phase when completed, Centrosome duplicates

G2

Cell continues to grow and prepare for cell division by checking DNA for any errors made in replication. Also checks for MPF and replicates organelles

MPF

mitosis promoting factor, needs to be present in adequate amounts for cell cycle continuation

Cell cycle regulations

Functional limitations- Surface volume ration (S/V)

Cell Specific Regulation- Cell Specific Checkpoints, CDK’s, Growth Factor, Density Dependent inhibition, anchorage dependance

Surface to Volume Ratio (S/V)

as a cell grows its volume increases MORE than its surface, cell division will only occur if the surface area is smaller than the volume (S/V decreases)

G1 Checkpoint

restriction point checks for favorable conditions to grow, enters G0 if unfavorable for growth

G2 Checkpoint

restriction point checks accuracy of DNA replication and MPF levels

M Checkpoint

during metaphase, checks for chromosomal attachment to spindle fibers

Cyclin Dependent Kinases (CDK’s)

phosphorylate certain substances to signal cell cycle progression, activated by cyclin

Growth Factors

Bind to receptors in the plasma membrane to signal for cell division

Density Dependent Inhibition

halting of cell division when density of cells is high

Anchorage dependance

cells divide only when attached to an external source

Microtubule Organizing Centers (MTOC’s)

eukaryotic cells, organize extensions of microtubules, responsible for forming the spindle apparatus which guides chromosomes during karyokinesis

Kinetochore Microtubules

extend from centrosomes and attach to kinetochores on chromosomes

astral microtubules

extend from centrosomes to the cell membrane to orient the spindle apparatus

polar microtubules

extend from the two centrosomes and connect with each other, they push centrosomes to opposite ends of the cells

Centrosomes

located near the nucleus and contain a pair of centrioles oriented at 90 degree angels to one another, replicate during the s phase of the cell cycle so that each daughter cell after cell division has one centrosome

Four Components of Mitosis (M Phase)

Prophase, Metaphase, Anaphase, Telophase

Prophase

chromatin DNA condense into chromosomes, the nucleolus and nuclear envelope disappear, spindle apparatus forms

Metaphase

chromosomes line up in single file along the metaphase plate (midpoint of the cell) guided by the spindle fibers

Anaphase

kinetochore microtubules shorten to pull sister chromatids apart. The sister chromatids are now considered separate chromosomes (2n)

telophase

chromosomes have segregated and nuclear membranes reform, the nucleoli reappear and chromosomes decondense into chromatin

Cleavage Furrow

contractile ring of actin microfilaments and myosin motors that pinch the cell in two, animal cells late in anaphase

Cell Plate

created by vesicle from the Golgi apparatus, produces middle lamella (cements plant cells together. plant cells in telophase

Binary Fission

organisms replicate their genome while cell division is happening, replicated NDA segregate to opposite ends of the cell and a septum forms to seperate into two new cells. Used by archea, bacteria, and certain organeless (mitochondria and chloroplast) to reproduce

Meiosis

four haploid daughter cells created from one diploid parents cell, by repeated the steps of karyokinesis twice

Meiosis I

produces two haploid cells through separation of homologous chromosomes

Prophase I

Chromatin condenses into chromosomes, nucleolus and nuclear membrane disappear, crossing over of homologous chromosomes, synapsis

Synapsis

Pairing of homologous chromosomes to form tetrads

Tetrads (bivalents)

pair of two homologous chromosomes each with two sister chromatids

Chiasmata

where two chromosomes of a homologous pair cross over during synapsis causing genetic recombination

Genetic Recombination

Exchange of DNA between two chromosomes to produce genetically diverse offspring

Metaphase I

tetrads randomly line up double-file on the metaphase plate, contributes to genetic diversity

Anaphase I

Kinetochore microtubules shorten to separate homologous chromosomes from each other

Telophase and Cytokinesis I

after tetrads have been pulled to opposite poles, nuclear membranes reform. Nucleoli reappears, cell plate or cleavage furrow

Meiosis II

Very similar to mitosis, sister chromatids are separated. Two haploid cells divide into four haploid daughter cells

Prophase II

chromatin condenses into chromosomes, nucleoli and nuclear envelope disappear, spindle apparatus reforms, no crossing over

Metaphase II

Sister chromatids line up single file on the metaphase plate, just like in mitosis

Anaphase II

Kinetochore microtubules shorten and pull sister chromatids apart, they becomes separate and the chromosome number doubles

Telophase and Cytokinesis II

nuclear membrane reforms, nucleoli reappear, chromosomes condense into chromatin. Four haploid daughter cells are produced in total

92

during S phase of the cell cycle a humans chromosomes are duplicated, into ____ chromatids

46, 92

During anaphase of meiosis I homologues chromosomes split up resulting in ____chromosomes and _ chromatids

23, 23

During anaphase of meiosis II result in ___ chromosomes and ___ chromatids in each daughter cell