Meiosis

JL Broadhurst201242029

What is meiosis?

Cell division for sex-cells.Sex Cells:

Are also called Gametes.

You know them as SPERM and EGG cells

What happens?

2 divisions: Meiosis I and Meiosis II

Starting with ONE (diploid) cell, ending with FOUR (haploid) cells.

Meiosis I

Meiosis II

Interphase: Chromosomes duplicate and build up energy for meiosis

Stages of Meiosis

Meiosis IProphase I

Metaphase IAnaphase ITelophase I

Meiosis IIProphase II

Metaphase IIAnaphase IITelophase II

Meiosis IProphase I

Prophase I- chromosome becomes visible and the nuclear membrane disappears; homologous chromosome appears and share fragments called crossing over

What does “crossing over” cause????

More genetic DIVERSITY!!

Meiosis IMetaphase I

- complete disappearance of nuclear membrane and appearance of spindle fiber; centromeres attached to the spindle fiber and lies on the metaphase plate.

Meiosis IAnaphase I

homologous chromosome separates from each other but centromere do not divide; chromosome continues to consists of two chromatids

Meiosis ITelophase I

chromosomes are still doubled; nuclear membrane is formed and disappearance of spindle fiber

Meiosis II Prophase II

cells have one chromosome

Meiosis IIMetaphase II

chromosomes align at the metaphase plate; centromeres divide thus separating the chromatids

Meiosis IIAnaphase II

each new daughter cell move towards opposite poles

Meiosis IITelophase II

spindle disappears; nuclear membrane is formed; nuclei are formed and cytokinesis happens

Comparing Mitosis and Meiosis Mitosis makes

cells for growth, development, repair, and is a form of asexual reproduction

Meiosis makes gametes for sexual reproduction

Comparing Mitosis and Meiosis

Mitosis produces two cells identical to the parent cell (diploid - called daughter cells)

Meiosis produces four cells with half the number of chromosomes as the parent (haploid)

Comparing Mitosis and Meiosis

In the first cell division, CHROMOSOME PAIRS (HOMOLOGOUS CHROMOSOMES) are separated.

In the second cell division, SISTER CHROMATIDS are pulled apart.

Comparing Mitosis and Meiosis In meiosis, “crossing

over” occurs during prophase I.

Chromosomes form tetrads

Homologous chromosomes “swap” parts of their DNA leads to recombination, or genetic variation

Reference list: http://www.slideshare.net/imkaelah/meiosis-lesson?qid=bf07a3ac-c563-4350-af21-

a255071068Meiosis lessonby imkaelah on Jul 24, 2013 http://

www.slideshare.net/mmravagnan/powerpoint-meiosis?qid=bf07a3ac-c563-4350-af21-a255071068ef&v=qf1&b=&from_search=18

Powerpoint meiosisby Magdalena Ravagnan, Veterinaria, Biology teacher from Argentina on Jun

16,2013 http://www.slideshare.net/MRKALEMBER/meiosis-in-depth?qid=bf07a3ac-c563-4

350-af21-a255071068ef&v=qf1&b=&from_search=3

Meiosis in depthby Jeff Kalember on Jan 30, 2014 http://www.slideshare.net/mjurkiewicz/meiosis-29211193?qid=bf07a3ac-c563-43

50-af21-a255071068ef&v=qf1&b=&from_search=9

Meiosisby mjurkiewicz on Dec 14, 2013 http://www.slideshare.net/rozeka01/biology-unit-4-cell-division-meiosis-notes?qi

d=bf07a3ac-c563-4350-af21-a255071068ef&v=qf1&b=&from_search=10

Biology unit 4 cell division meiosis notesby rozeka01 on Dec 12, 2013