Meiosis & Sexual Reproduction
description
Transcript of Meiosis & Sexual Reproduction
![Page 1: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/1.jpg)
2007-2008AP Biology
Meiosis &Sexual Reproduction
![Page 2: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/2.jpg)
AP Biology
Cell division / Asexual reproduction Mitosis
produce cells with same information identical daughter cells
exact copies clones
same amount of DNA same number of chromosomes same genetic information
Aaaargh!I’m seeing
double!
![Page 3: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/3.jpg)
AP Biology
Asexual reproduction Single-celled eukaryotes
yeast (fungi) Protists
Paramecium Amoeba
Simple multicellular eukaryotes Hydra
What are thedisadvantages of
asexual reproduction?
What are the advantages?
budding
budding
![Page 4: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/4.jpg)
AP Biology
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?
46 46+ 92
egg sperm zygote
What if we did, then….
Doesn’t work!
![Page 5: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/5.jpg)
AP Biology
Human female karyotype
46 chromosomes23 pairs
![Page 6: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/6.jpg)
AP Biology
Human male karyotype
46 chromosomes23 pairs
![Page 7: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/7.jpg)
AP Biology
Homologous chromosomes Paired chromosomes
both chromosomes of a pair carry “matching” genes control same inherited characters homologous = same information
diploid2n
2n = 4
single stranded homologous
chromosomes
double strandedhomologous chromosomes
![Page 8: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/8.jpg)
AP Biology
How do we make sperm & eggs? Must reduce 46 chromosomes 23
must half the number of chromosomes
23
2346
egg
sperm
46
meiosis 46
fertilization
23
23
gametes
zygote
![Page 9: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/9.jpg)
AP Biology
Meiosis: production of gametes Alternating processes,
alternating stages chromosome number
must be reduced diploid haploid 2n n
humans: 46 23 meiosis reduces
chromosome number makes gametes
fertilization restores chromosome number haploid diploid n 2n
![Page 10: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/10.jpg)
AP Biology
Sexual reproduction lifecycle
_______ _______ _______
_______ _______ _______
_______ _______ _______
fertilization fertilization
![Page 11: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/11.jpg)
AP Biology
Meiosis Reduction Division
special cell division in sexually reproducing organisms
reduce 2n 1n diploid haploid
“half” makes gametes
sperm, eggs
Warning: meiosis evolved from mitosis, so stages & “machinery” are similar but the processes are radically different. Do not confuse the two!
![Page 12: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/12.jpg)
AP Biology
Overview of meiosisI.P.M.A.T.P.M.A.T
interphase 1 prophase 1 metaphase 1 anaphase 1
telophase 1
prophase 2 metaphase 2 anaphase 2 telophase 2
2n=4
n=2
![Page 13: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/13.jpg)
AP Biology
2nd division of meiosis separates sister chromatids
1st division of meiosis separates homologous pairs
Double divisionof meiosis
DNA replication
Meiosis 1
Meiosis 2
![Page 14: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/14.jpg)
AP Biology
2n = 6 double
stranded
2n = 6 single
stranded
Preparing for meiosis 1st step of meiosis
Duplication of DNA Why bother?
meiosis evolved after mitosis convenient to use
“machinery” of mitosis DNA replicated in
S phase of interphase of MEIOSIS(just like in mitosis)
M1 prophase
![Page 15: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/15.jpg)
AP Biology
2n = 4 single
strandedMeiosis 1
2n = 4double
strandedprophase 1
1st division of meiosis _________________________
tetrad
synapsis
1n = 2double
stranded
telophase 1
2n = 4double
strandedmetaphase 1
![Page 16: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/16.jpg)
AP Biology
Meiosis 2
1n = 2double
strandedmetaphase 2
1n = 2single
stranded
telophase 2
prophase 2
1n = 2double
stranded
2nd division of meiosis _________________________
What doesthis division
look like?
4
![Page 17: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/17.jpg)
AP Biology
Steps of meiosis Meiosis 1
interphase prophase 1 metaphase 1 anaphase 1 telophase 1
Meiosis 2 prophase 2 metaphase 2 anaphase 2 telophase 2
2nd division of meiosis separates sister chromatids
(1n 1n)
* just like mitosis *
1st division of meiosis separates homologous pairs
(2n 1n)
“reduction division”
![Page 18: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/18.jpg)
AP Biology
![Page 19: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/19.jpg)
AP Biology
![Page 20: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/20.jpg)
AP Biology
Trading pieces of DNA Crossing over
during Prophase 1, sister chromatids intertwine synapsis homologous pairs swap
pieces of chromosome DNA breaks & re-attaches
tetrad
synapsis
prophase 1
![Page 21: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/21.jpg)
AP Biology
Crossing over 3 steps
cross over breakage of DNA re-fusing of DNA
New combinations of traits
What are theadvantages of
sexual reproduction?
![Page 22: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/22.jpg)
AP Biology
Meiosis 1
![Page 23: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/23.jpg)
AP Biology
Meiosis 2
![Page 24: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/24.jpg)
AP Biology
Mitosis vs. Meiosis
![Page 25: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/25.jpg)
AP Biology
Mitosis vs. Meiosis Mitosis
___________________ ___________________
___________________ ___________________
___________________ ___________________ ___________________
___________________ ___________________
Meiosis ___________________ ___________________
___________________ ___________________
___________________ ___________________ ___________________
___________________ ___________________
![Page 26: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/26.jpg)
AP Biology
mitosis
zygote
Putting it all together…
23
2346
egg
sperm
46
meiosis 4623
23
fertilization mitosis &development
meiosis fertilization mitosis + development
46
46
46
46
46
4646 46
gametes
![Page 27: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/27.jpg)
AP Biology
The value of sexual reproduction Sexual reproduction introduces genetic variation
genetic recombination during meiosis independent assortment of chromosomes
random alignment of homologous chromosomes in Meiosis 1
crossing over random fertilization
which sperm fertilizes which egg?
Driving evolution variation for natural selection
metaphase1
![Page 28: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/28.jpg)
AP Biology
Variation from genetic recombination Independent assortment of chromosomes
meiosis introduces genetic variation gametes of offspring do not have same
combination of genes as gametes from parents random assortment in humans produces
223 (8,388,608) different combinations in gametes
from Dadfrom Mom offspringnew gametes
made by offspring
![Page 29: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/29.jpg)
AP Biology
Variation from crossing over Crossing over creates completely new
combinations of traits on each chromosome from 8 million different gametes “immeasurable”
![Page 30: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/30.jpg)
AP Biology
Variation from random fertilization Sperm + Egg = ?
any 2 parents will produce a zygote with over 70 trillion (223 x 223) possible diploid combinations
![Page 31: Meiosis & Sexual Reproduction](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813b9d550346895da4d44c/html5/thumbnails/31.jpg)
AP Biology
Differences across kingdoms Not all organisms use haploid & diploid
stages in same way which one is dominant (2n or n) differs but still alternate between haploid & diploid
must for sexual reproduction