MEIOSIS HOW SEX CELLS ARE MADE!

Make gametes by..... MEIOSIS!!!!!!!!! Meiosis forms haploid cells.

INTERPHASE OCCURS ONCE G and S phases help enlarge the cell and replicate the genetic material Prepares the cell for nuclear division

1. PROPHASE I Chromosomes become visible. Nuclear Envelope disappears Crossing over can occur.

2. METAPHASE I Chromosomes line up in the middle

3. ANAPHASE I homologous pairs move to opposite poles

4. TELOPHASE I Cytokinesis

5. PROPHASE II no interphase! New spindles form

6. METAPHASE II Chromosomes line up again

7. ANAPHASE II Centromeres divide Chromatids move apart

8. TELOPHASE II CYTOKINESIS

meiosis contributes to genetic variation. RESULTS............ 4 Haploid cells! meiosis contributes to genetic variation.

Gamete formation in male & female animals involves meiosis. Sperm are formed by spermatogenesis 4 sperm are made by meiosis

Ova (eggs) are made by oogenesis. Only 1 egg results. The other 3 are called polar-bodies. The polar bodies die

SEXUAL VS. ASEXUAL REPRODUCTION

SEXUAL REPRODUCTION... 2 parents form haploid gametes. The offspring will have traits of both parents. Advantage: mixes genes Disadvantage: numbers are limited

ASEXUAL REPRODUCTION produces offspring that are clones of parents advantage: makes many babies in short time disadvantage: no diversity in unstable environments

Examples of asexual reproduction: binary fission: bacteria budding: sponges fragmentation: sea stars