Meiosis & Sexual Reproduction Regents Biology 2006-2007 Cell division / Asexual reproduction Mitosis produce cells with same information identical daughter cells exact copies clones same number of chromosomes
same genetic information Regents Biology Aaaargh! Im seeing double! Asexual reproduction Single-celled eukaryotes yeast Paramecium Amoeba Simple multicellular eukaryotes Hydra budding What are the
disadvantages of asexual reproduction? Regents Biology What are the advantages? How about the rest of us? What if a complex multicellular organism (like us) wants to reproduce? joining of egg + sperm Do we make egg & sperm by mitosis? No! What if we did, then. 46 egg
XX Regents Biology diploid = 2 copies 2n Human male karyotype 46 chromosomes 23 pairs XY Regents Biology How do we make sperm & eggs? Must reduce 46 chromosomes 23 must half the number of chromosomes haploid 23
Meiosis makes sperm & eggs 46 chromosomes to 23 chromosomes half the number of chromosomes 23 46 meiosis 46 diploid Regents Biology egg 23 sperm haploid
Paired chromosomes Homologous chromosomes both chromosomes of a pair carry matching genes control same inherited characters homologous = same information diploid 2n 2n = 4 Regents Biology eye color (brown?) eye color (blue?) homologous
chromosomes double stranded homologous chromosomes double stranded Meiosis 1 overview 1st division of meiosis Copy DNA Line Up 1 prophase 1 metaphase 1 4 chromosomes diploid 2n Regents Biology
Divide 1 gamete telophase 1 2 chromosomes haploid 1n Bye Bye 2 Meiosis 2 overview telophase 2 telophase 1 Line Up 2 2nd division of meiosis
looks like mitosis 2 chromosomes haploid Regents Biology 1n metaphase 2 gametes 4 Meiosis = reduction division Meiosis special cell division in sexually reproducing organisms reduce number of chromosomes
2n 1n diploid haploid half makes gametes sperm, eggs Regents Biology Meiosis & mitosis Meiosis to make gametes sperm & egg Mitosis to make copies of cells growth
repair development Regents Biology Sexual reproduction lifecycle 2 copies diploid 2n 1 copy haploid 1n fertilization Were mixing things up here! A good thing? Regents Biology meiosis
1 copy haploid 1n Putting it all together meiosis fertilization mitosis + development gametes 46 meiosis 46 23 egg 23 23 23
zygote fertilization Regents Biology sperm 46 46 46 46 46 46 46 46 46 mitosis & mitosis development The value of meiosis 1 Consistency over time
meiosis keeps chromosome number same from generation to generation from Mom Mom Dad offspring from Dad Regents Biology The value of meiosis 2 Change over time Were mixing things up here! meiosis introduces genetic variation
gametes of offspring do not have same genes as gametes from parents new combinations of traits from Dad variation from Mom offspring Regents Biology new gametes made by offspring How does this explain: family resemblance & differences! Why are the kids so similar to the parents but not exact? Michael & Kirk Douglas
Regents Biology Baldwin brothers Martin & Charlie Sheen, Emilio Estevez What are the advantages of asexual reproduction? What are the DISadvantages of asexual reproduction? Any Questions?? What are the advantages of sexual reproduction? Regents Biology
What are the DISadvantages of sexual reproduction? 2006-2007
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