Cell Reproduction Two types of reproduction:

Mitosis: Purpose = produces regular body cells for growth and repair

Meiosis: Purpose = produces sex cells only

http://tbn2.google.com/images?q=tbn:spK6vnBHuv7DlM:http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

Cell Cycle

Interphase Mitosis

Prophase Metaphase Anaphase Telophase

Cytokinesis

MEIOSIS A different type of cell division!

Only occurs for the purpose of producing gametes (= sex cells)

Only occurs in reproductive organs (Animals = testes and ovaries)

Meiosis Each chromosome

begins meiosis by finding its match to make a pair

1 chromosome in each pair comes from the father and 1 from the mother

Meiosis A matching pair of chromosomes is called

HOMOLOGOUS (= the same) Homologous chromosomes contain genes

for the same traits

Meiosis v.s. MitosisProphase 1 of Meiosis: Homologous chromosomes line up together = TETRAD

Meiosis vs. Mitosis Homologous chromosomes are

the same size their centromeres are in the same position they have the same number of genes, arranged in the

same order.

Meiosis v.s. Mitosis Chromosomes swap

alleles during Prophase 1.

Swapping alleles = crossing over

This increases genetic diversity NO two people are exactly alike

Meiosis v.s. Mitosis Meiosis - Number of Daughter Cells =

FOUR Mitosis – Number of Daughter Cells = TWO

Meiosis v.s. Mitosis

In meiosis each daughter cell has HALF the number of chromosomes as the parent cell.

In mitosis each daughter cell has the SAME number of chromosomes as the parent cell.

Meiosis, What’s the big deal? • Meiosis is the reason that in

sexually reproducing organisms• genetic information varies

between parent and offspring,• Genetic information varies

between offspring from the same parents.

• Ensures genetic variation, which is essential for evolution.

• The genes/traits of a species change from generation to generation.

Meiosis

MEIOSIS: to make sex cells with half the

original DNA.

Parent cell

4 daughter cells with half of DNA from parent cell

Mitosis vs. Meiosis

Parent cell

2 daughter cells with identical DNA to parent cell

4 daughter cells with half of DNA from parent cell

Parent cell

4 gametes

Vocabulary for Bio Somatic cell: a body cell that has the organisms

complete diploid set of chromosomes. Diploid = a cell that contains both sets of homologous

chromosomes from the parent.

Gamete: sex cell, sperm or egg cell containing the haploid set of chromosomes Haploid = a cell containing 1 set of genes

In Humans

46 chromosomes in somatic (body) cells 23 chromosomes in sperm cells and egg cells

(gametes). During fertilization a sperm fertilizes an egg

producing a zygote with 46 chromosomes. Through the process of MITOSIS the zygote

grows and develops into a human baby.

http://www.miscarriage.com.au/images/pages/karyotype_normal.jpg

AND FINALLY Mitosis: results in two daughter cells with

identical chromosomes and the exact same number of chromosomes as the parent cell.

Meiosis: results in four cells with different chromosomes and half the number of chromosomes as the parent cell*.