Meiosis

the process of nuclear division in sexual reproduction where the number of the chromosomes is halved.

produces four daughter cells all daughter cells are haploid (half the

set) chromosomes are shuffled in the process,

so that each daughter cell has a unique combination

used to create gametes (sperm and egg)

# of Divisions

Type of Reproduct

ion Cells

ProducedTotal # of

Cells at the End

1 2

Asexual Sexual

Body Cells Sex cells

2 identical Diploid (2n)

cells

4 not identical Haploid (n)

cells

Total # of Chromosomes

in the End

Crossing Over

Number of Steps

46 23

No Yes

4- PMAT8- PMAT IPMAT II

Sexual Asexual

Involves the fusion of gametes (Egg and Sperm)

COMBINES GENES FROM TWO DIFFERENT PARENTS TO FORGENETICALLY DIVERSE OFFSPRING.

1.Prophase- Each Chromosome pairs up

2. Metaphase- Line up in the middle

3. Anaphase- Chromosomes pull apart.

4. Telephase- Cell separates in 2 cells

5. Prophase II- Chromosomes pair again in the 2 haploid cells.

6. Metaphase II- Line up in the middle

7. Anaphase II- Chromosomes pull apart

8. Telephase/Cytokinesis- Result in 4 haploid (N) daughter cells.

Crossing Over- homologous chromosomes exchange portions of their chromatids resulting in the exchange of alleles, producing NEW COMBINATIONS!!

The following images show three separate possibility for a single cell that has undergone meiosis. Look at all the different combinations

Independent Assortment- In addition to Crossing-Over, the process of meiosis ensures that chromosomes are randomly assorted.

THE 23RD PAIR, THE SEX CHROMOSOMESDETERMINES WHETHER THE PERSON IS FEMALE (XX) OR MALE (XY)

http://www.biologycorner.com/bio1/meiosis.html

http://teachers.dadeschools.net http://www.web-books.com/MoBio/

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pictures/samples/personal/pregnant%20pics1.jpg