Mitosis And Meiosis

LAB 6

MITOSIS & MEIOSIS

B A L

6

MITOSIS

MITOSIS

WHAT IS MITOSIS? •A

Process in which a parent nucleus produces 2 daughter nuclei • Each having the same number and kinds of chromosomes as the parent nucleus.

MITOSIS PERMITS GROWTH & TISSUE REPAIR.

MITOSIS REPAIRS DAMAGED TISSUE AND BONE.

CELL CYCLE

Interphase S Growth DNA replications

G 1

G2 Growth and final preparations for division

Anaphas e

ase

ki n

Tel oph

Mitosis

Spindle assembly checkpoint if chromosome is not aligned properly mitosis will not occur

M

Pr o

es

se

Cy to

as e Metaph se ha p eta m o Pr

is

G1 Growth

ph a

Cell cycle checkpoint Apoptosis occur if DNA is damaged and cannot be repaired

Mitosis checkpoint Apoptosis occur if DNA damaged and cannot be repaired.Mitosis occur if DNA replicate properly

G 2

MITOTIC STAGES

PROPHASE

• The chromatin condenses into discrete chromosomes. • Nucleolus disappears • The nuclear envelope breaks down • Spindles form at opposite "poles" of the cell.

METAPHASE

• The duplicated chromosomes are aligned at the metaphase plate. • Kinetochore spindle fiber attach to sister chromatids

ANAPHASE

• The sister chromatids part and become daughter chromosomes that move to opposite ends of the cell.

TELOPHASE

• Nuclear envelopes and nucleolus reappear. •Daughter cells form •Chromosomes become indistinct chromatin. • Cytokines has started between the two groups of chromosomes

CYTOKINESIS (Division of the cytoplasm)

IN ANIMAL CELLS

• Cleavage furrowing process occurs. • A band of actin filaments slowly forms a circular contraction between the 2 daughter cells

IN PLANTS CELLS

• Formation of new cell plate between the daughter cells, which eventually becomes new plasma membrane between the daughter cells.

The word "meiosis" comes from the Greek verb meioun, meaning "to make small,"

A process of reductional division in which the number of chromosomes per cell is cut in half.

Prophase I takes the most time. Chromosomes begin to condense. Cell is 2N (diploid) and 2 chromatids/chromosomes (like before mitosis). Synapsis occurs: homologous chromosomes pair, their DNA aligns. Crossing over may occur: chromosomes exchange homologous loci (between homologous pairs). The point of crossing over is called the chiasma.

Homologous chromosomes align at cell equator to form tetrads.

Chromosomes are pulled to either side of the dividing cell; one of each pair is pulled toward each pole.

The nuclear envelope may form again.

Two daughter cells are formed.

Nuclear envelope disperses

Chromosomes align between poles

Chromatids segregate.

The former sister chromatids have reached the poles. A   nuclear envelop is formed around each nucleus, while chromosome despiralize again.

After cytokinesis, four daughter cells are formed.  

Comparing Meiosis and Mitosis Chromosome behavior •Mitosis: Homologous chromosomes independent •Meiosis: Homologous chromosomes pair forming bivalents until anaphase I Chromosome number •Mitosis- daughter cells diploid •Meiosis- daughter cells haploid Genetic identity of progeny: