4. cell division

I. GENERAL

A. REVIEW DNA1. NUCLEOTIDE

2. DOUBLE HELIX – two nucleotide chains

C-G A-T

II. CELL CYCLE

A. GENERAL

1. DIAGRAM

G1

S

G2

MITOSIS

2. DEFINITIONS

a. DNA – A double helix molecule polymer with geneticinformation.

b. GENE – A segment of DNA that codes for a specifictrait.

c. CHROMATIN – Uncondensed structures made ofDNA & proteins found in the nucleus withgenes on it.

d. CHROMOSOME – A condensed structure of DNA &

proteins found in the nucleus with genes on it.

1 chromosome

1 chromatid = a single DNA molec.1 chromosome

2 chromatids = two DNA molec.

Gene 1

Gene 2

Gene 3

e. DIPLOID – An individual (cell, etc.) has 1 pair of chromosomes with the same genes. The chromosomes can have 1 or 2 chromatids each.

or

f. HAPLOID – An individual (cell, etc.) has 1 chromosome with specific genes. The chromosome can have 1 or 2 chromatids each.

or

g. HOMOLOGOUS PAIR – two chromosomes in a single cell that have the same genes. Found in diploid organisms.

Homologous pair where the chromosomes of the pair have only one chromatid.

Homologous pair where the chromosomes of the pair have two chromatids.

B. PROKARYOTIC CELL DIVISION

BINARY FISSION

C. EUKARYOTIC CELL CYCLE

C1. INTERPHASE

– 90% cell life

– Where the cell spends most of its life

C2. CELL DIVISION (2 TYPES)

MITOSISMEIOSIS

1. DIVIDE

2. # TIMES 1 2

3. WHERE (humans = all cells) (humans=gonads)

4. FUNCTION replace old cells sexual reproductiongrowthasexual reproduction

Mother cell Daughter cells

Interphase

MITOSIS

A. PHASES – diploid organism

prophase

metaphase

anaphase

telophase & cytokinesis

Prophase1. Chromatin into chromosomes

2. Nuclear envelope disintegrates

3. Spindle fibers form near the nucleus and some attach to kinetochores

4. Centrioles start to

move to opposite poles.

Metaphase

Chromosomes line up along the equator.

AnaphaseThe spindle fibers are shortened at the kinetochore which

causes the chromatids to be pulled apart and moved to

opposite poles.

TelophaseChromatids are at opposite poles, start to reform nuclear

membrane, spindle fibers start to disappear.

CYTOKINESISIn animal cells the membrane pinches off to form 2 new

cells, reform chromatin and nucleus .

Overall

III. MEIOSIS - general

Two cell divisions where the resulting

daughter cells have ½ the number of

chromosomes as the originals.

46

23

23

23

23

23

23

MI MII

Prophase I of Meiosis I

Nuclear membrane starts to disintegrate.

Chromatin to chromosomes. Centrioles move. Form spindle fibers.

Homologous Pairs form chiasma where can get

crossing-over (exchange of genetic material) = recombination

Metaphase I of Meiosis IHomologous pairs line up along the equator.

Independent Assortment – the chromosomes arrange themselves independent of the other homologous pairs.

Type of recombination.

Anaphase I of Meiosis I

The spindle fibers shorten and pull apart the chromosomes

of the homologous pairs.

Telophase I of Meiosis I

The chromosomes reach opposite poles and start to form nuclear membrane and disintegrate spindle fibers.

Cytokinesis

Divide cell contents.

The two new cells each contain ½ the number of chromosomes as the original cell (each chromosome has two chromatids).

The chromosomes reach opposite poles and start to form nuclear membrane and disintegrate spindle fibers.

Prophase of Meiosis II

Re-condense chromosomes if they uncondensed and

replicate the centrioles.

Spindle fibers form and centrioles move to opposite poles.

Metaphase of Meiosis II

Chromosomes line up along equator.

Spindle fibers attached.

Anaphase of Meiosis II

Spindle fibers exert force to pull chromatids apart.

Telophase of Meiosis II

Chromosomes reach the opposite poles and start to reform nuclear membranes.

CytokinesisSplit the cell contents so that end up with four haploid cells.