25meiosis

2006-2007 Meiosis & Sexual Reproduction

Cell division / Asexual reproduction ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Aaaargh! I ’ m seeing double!

Asexual reproduction ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],What are the disadvantages of asexual reproduction? What are the advantages?

How about the rest of us? ,[object Object],[object Object],[object Object],46 46 + 92 egg sperm zygote What if we did, then…. Doesn’t work! No!   

Human female karyotype 46 chromosomes 23 pairs XX diploid = 2 copies 2n

Human male karyotype 46 chromosomes 23 pairs XY diploid = 2 copies 2n

How do we make sperm & eggs? ,[object Object],[object Object],[object Object],gametes egg sperm meiosis fertilization zygote 23 23 46 46 46 23 23

Meiosis makes sperm & eggs ,[object Object],[object Object],egg sperm meiosis haploid diploid 23 23 46 46

Paired chromosomes ,[object Object],[object Object],[object Object],[object Object],diploid 2n 2n = 4 homologous chromosomes double stranded homologous chromosomes eye color (brown?) eye color (blue?)

Meiosis 1 overview ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],double stranded Copy DNA Line Up 1 Divide 1 gamete prophase 1 metaphase 1 telophase 1

[object Object],[object Object],Meiosis 2 overview ,[object Object],[object Object],[object Object],gametes Line Up 2 Bye Bye 2 telophase 1 metaphase 2 telophase 2 4

Meiosis = reduction division ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Meiosis & mitosis ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Sexual reproduction lifecycle ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],meiosis fertilization We ’ re mixing things up here ! A good thing?

Putting it all together… ,[object Object],mitosis zygote egg sperm meiosis fertilization mitosis & development gametes 23 23 46 46 46 23 23 46 46 46 46 46 46 46 46

The value of meiosis 1 ,[object Object],[object Object],from Mom from Dad offspring Dad Mom

The value of meiosis 2 ,[object Object],[object Object],[object Object],[object Object],from Mom from Dad new gametes made by offspring offspring We ’ re mixing things up here ! variation

How does this explain: family resemblance & differences! ,[object Object],Martin & Charlie Sheen, Emilio Estevez Michael & Kirk Douglas Baldwin brothers

Any Questions?? 2006-2007 What are the DIS advantages of asexual reproduction? What are the DIS advantages of sexual reproduction? What are the advantages of sexual reproduction? What are the advantages of asexual reproduction?

25meiosis

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