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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 Chromosome s 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 Chromosome s line up again 7. ANAPHASE II Centromeres divide Chromatids move apart 8. TELOPHASE II CYTOKINESI S 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