Mitosis/Cell Division Review

B

C

D

E

A

Meiosis -Produces gametes or sex cells (sperm and egg cells) -Occurs ONLY in the reproductive organs

Products of Meiosis = 4 new cells

ANDDivides the chromosome

number in half

For Example:

Parent Cell

4 daughter cells

2 Sets of Divisions

1st division is exactly like mitosis except sister chromatids stay together

Before the 1st division takes place DNA MUST replicate

Prophase I• Chromosomes condense

• Homologous chromosomes pair together

• Crossing over occurs

Crossing Over

Metaphase I• Homologous pairs are moved to the equator (middle) of the cell

Anaphase I • Homologous pairs separate

•Chromatids remain together

•Genetic material has been recombined

Telophase I

•Chromosomes gather at poles•Cytoplasm divides

2nd DIVISION BEGINS

DNA replication DOES NOT

occur

Prophase 2• New spindles form around chromosomes

• Crossing over – does not occur!

Metaphase 2• Chromosomes align along with equator (middle) of the cells

Anaphase 2

• Sister chromatids (now called chromosomes) divide and move to opposite poles

Telophase 2•Chromosomes gather at the poles

•Nuclear envelope forms and cytoplasm divides

4 new daughter cells, each genetically DIFFERENT, are formed and are all haploid

Sexual Reproduction• Haploid cells join to make diploid cells

• Increase in genetic variation

• Leads to change or evolution

Females: meiosis occurs before birthEach month, one egg is matured

and released for possible fertilization

Males: meiosis begins at puberty and continues until death

Asexual Reproduction•Single parents pass genes to offspring

Clones

Prokaryotes, yeast, hydra

Faster to produce offspring, but no genetic variation

GENETIC VARIATION • The chromosome a gamete will receive depends on the way it lines up at the equator

Independent

assortment

The Importance• Lead to the evolution of a species• Increase survival

CANCER• Cells have checkpoints to determine if they are healthy enough to divide

• If those checkpoints are faulty, cells can divide and grow uncontrollable – can form a tumor and lead to cancer

What’s the problem with more cells?

1.) Steal nutrients from healthy cells which eventually die

2.) Can travel from their original location

METASTASIZE

Causes of Cancer• Exposure to chemicals or toxins

• Radiation

• Viruses

• Your Own Genetics