meiosis. meiosis cell divisiongametes, half chromosomes, the form of cell division by which...
TRANSCRIPT
![Page 1: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/1.jpg)
![Page 2: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/2.jpg)
![Page 3: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/3.jpg)
MEIOSIS
The form of cell divisioncell division by which gametes, gametes, with halfhalf the number of chromosomes,chromosomes, are produced.
Diploid (2n) Diploid (2n) haploid (n)haploid (n)
MeiosisMeiosis is sexual reproduction.sexual reproduction.
Two divisionsTwo divisions (meiosis I meiosis I and meiosis IImeiosis II).
![Page 4: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/4.jpg)
MEIOSISMEIOSIS
Sex cells Sex cells divide to produce gametesgametes (sperm (sperm or egg)or egg).
GametesGametes have halfhalf the # of chromosomeschromosomes.
Occurs only in gonads (testes or ovaries).Occurs only in gonads (testes or ovaries).
Male: spermatogenesisMale: spermatogenesis
Female: oogenesisFemale: oogenesis
MeiosisMeiosis is similar to mitosismitosis with some chromosomal differences.
![Page 5: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/5.jpg)
Produces two diploid daughter cells
Produces daughter cells that ARE genetically identical
Produce four haploid daughter cells
Produces daughter cells that are NOT genetically identical
![Page 6: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/6.jpg)
SPERMATOGENESIS - SPERMATOGENESIS - FORMATION OF SPERM FORMATION OF SPERM
CELLSCELLS
2n=46
humansex cell
diploid (2n)
n=23
n=23
meiosis I
n=23
n=23
n=23
n=23
sperm
haploid (n)
meiosis II
![Page 7: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/7.jpg)
![Page 8: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/8.jpg)
![Page 9: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/9.jpg)
INTERPHASE IINTERPHASE I
Similar to mitosismitosis interphase.
ChromosomesChromosomes replicate (S phase).(S phase).
Each duplicated chromosomechromosome consist of two identical sister chromatidschromatids attached at their centromerescentromeres.
CentrioleCentriole pairs also replicate.
![Page 10: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/10.jpg)
INTERPHASE IINTERPHASE I
NucleusNucleus and nucleolusnucleolus visible.
nuclear membrane
nucleolus
cell membrane
chromatin
![Page 11: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/11.jpg)
MEIOSIS I (FOUR PHASES)MEIOSIS I (FOUR PHASES)
Cell division Cell division that reduces the chromosomechromosome number by one-half.one-half.
four phasesfour phases:
a.a. prophase Iprophase I
b.b. metaphase Imetaphase I
c.c. anaphase Ianaphase I
d.d. telophase Itelophase I
![Page 12: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/12.jpg)
PROPHASE IPROPHASE I
Longest and most complex phase (90%).Longest and most complex phase (90%).
ChromosomesChromosomes condense.
SynapsisSynapsis occurs: homologous homologous chromosomes chromosomes come together to form a tetradtetrad.
TetradTetrad is two chromosomeschromosomes or four chromatidschromatids (sister and nonsister chromatids).
![Page 13: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/13.jpg)
PROPHASE IPROPHASE I - - SYNAPSISSYNAPSIS
Homologous chromosomes
sister chromatids sister chromatidsTetrad
![Page 14: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/14.jpg)
HOMOLOGOUS HOMOLOGOUS CHROMOSOMESCHROMOSOMES
Pair of chromosomeschromosomes (maternalmaternal and paternalpaternal) that are similar in shape and size.
Homologous pairs (tetrads) (tetrads) carry genes controlling the same inherited traits.
Each locuslocus (position of a gene) (position of a gene) is in the same position on homologues.
Humans have 23 pairs of homologous homologous chromosomes.chromosomes.
a. 22 pairs of autosomesautosomesb. 01 pair of sex chromosomessex chromosomes
![Page 15: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/15.jpg)
HOMOLOGOUS CHROMOSOMESHOMOLOGOUS CHROMOSOMES
Paternal Maternal
eye color locus
eye color locus
hair color locus
hair color locus
![Page 16: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/16.jpg)
CROSSING OVERCROSSING OVER
Crossing over (variation) Crossing over (variation) may occur between nonsister chromatidschromatids at the chiasmatachiasmata.
Crossing overCrossing over: segments of nonsister chromatidschromatids break and reattach to the other chromatidchromatid.
Chiasmata (chiasma) Chiasmata (chiasma) are the sites of crossing overcrossing over.
![Page 17: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/17.jpg)
CROSSING OVER - VARIATION CROSSING OVER - VARIATION
nonsister chromatids
chiasmata: site of crossing over
variation
Tetrad
![Page 18: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/18.jpg)
SEX CHROMOSOMESSEX CHROMOSOMES
XX chromosome - female XY chromosome - male
![Page 19: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/19.jpg)
PROPHASE IPROPHASE I
centriolesspindle fiber
asterfibers
![Page 20: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/20.jpg)
METAPHASE IMETAPHASE I Shortest phaseShortest phase TetradsTetrads align on the metaphase platemetaphase plate. INDEPENDENT ASSORTMENT OCCURS:INDEPENDENT ASSORTMENT OCCURS:
1. Orientation of homologous pair to poles is random.2. Variation3. Formula: 2n
Example:Example: 2n = 42n = 4then then n = 2 n = 2 thusthus 2 22 2 = 4 combinations= 4 combinations
![Page 21: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/21.jpg)
METAPHASE IMETAPHASE I
metaphase plate
OR
metaphase plate
![Page 22: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/22.jpg)
QUESTION:QUESTION:
In terms of In terms of Independent Independent AssortmentAssortment -how many different -how many different combinations of sperm could a combinations of sperm could a humanhuman malemale produce? produce?
![Page 23: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/23.jpg)
ANSWERANSWER
Formula: 2Formula: 2nn
Human chromosomes:Human chromosomes: 2n = 462n = 46
n = 23n = 23
222323 = ~8 million = ~8 million combinationscombinations
![Page 24: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/24.jpg)
ANAPHASE IANAPHASE I
Homologous chromosomes Homologous chromosomes separate and move towards the poles.
Sister chromatids Sister chromatids remain attached at their centromerescentromeres.
![Page 25: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/25.jpg)
ANAPHASE IANAPHASE I
![Page 26: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/26.jpg)
TELOPHASE ITELOPHASE I
Each pole now has haploidhaploid set of chromosomeschromosomes.
CytokinesisCytokinesis occurs and two haploid daughter cells are formed.
![Page 27: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/27.jpg)
TELOPHASE ITELOPHASE I
![Page 28: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/28.jpg)
Figure 2.3
Interkinesis
A short interphase between the two meiotic divisions
Chromosomes unfold into very thin threads
Proteins are manufactured
However, DNA is NOT replicated a second time
![Page 29: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/29.jpg)
MEIOSIS IIMEIOSIS II
No interphase II No interphase II (or very short - no more DNA replicationDNA replication)
Remember:Remember: Meiosis II Meiosis II is similar to mitosismitosis
![Page 30: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/30.jpg)
PROPHASE IIPROPHASE II
same as prophaseprophase in mitosismitosis
![Page 31: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/31.jpg)
METAPHASE IIMETAPHASE II
same as metaphasemetaphase in mitosismitosis
metaphase platemetaphase plate
![Page 32: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/32.jpg)
ANAPHASE IIANAPHASE II
same as anaphaseanaphase in mitosismitosis sister chromatids separatesister chromatids separate
![Page 33: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/33.jpg)
TELOPHASE IITELOPHASE II
Same as telophasetelophase in mitosismitosis.
Nuclei form.
CytokinesisCytokinesis occurs.
Remember:Remember: four haploid daughter four haploid daughter cells cells produced.produced.
gametes = sperm or egggametes = sperm or egg
![Page 34: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/34.jpg)
TELOPHASE IITELOPHASE II
![Page 35: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/35.jpg)
MEIOSISMEIOSIS
2n=4
sex cell
diploid (2n)
n=2
n=2
meiosis I
n=2
n=2
n=2
n=2
sperm
haploid (n)
meiosis II
![Page 36: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/36.jpg)
VARIATIONVARIATION
Important to population as the raw Important to population as the raw material for material for natural selectionnatural selection..
Question:Question:
What are the three sexual sources What are the three sexual sources ofof
genetic variation? genetic variation?
![Page 37: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/37.jpg)
ANSWER:ANSWER:
1. crossing over (prophase I)1. crossing over (prophase I)
2. independent assortment 2. independent assortment (metaphase I)(metaphase I)
3. random fertilization3. random fertilization
Remember: variation is good!
![Page 38: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/38.jpg)
Table 3.1
Comparison of Mitosis and Meiosis
![Page 39: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/39.jpg)
Interphase
CytokinesisTelophase Anapha
se
Metaphase
Prophase
What looks similar between mitosis and meiosis?What looks different?
![Page 40: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/40.jpg)
Figure 2.3
Meiosis vs. Mitosis Animation
Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.
![Page 41: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/41.jpg)
QUESTION:QUESTION:
A cell containing 20 chromosomes20 chromosomes (diploid)(diploid) at the beginning of meiosis would, at its completion, produce cells containing how many chromosomeschromosomes?
![Page 42: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/42.jpg)
ANSWER:ANSWER:
10 chromosomes (haploid)10 chromosomes (haploid)
![Page 43: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/43.jpg)
FERTILIZATIONFERTILIZATION
The fusion of a spermsperm and eggegg to form a zygotezygote.
A zygote is a fertilized egg
n=23egg
sperm n=23
2n=46zygote
![Page 44: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/44.jpg)
QUESTION:QUESTION:
A cell containing 40 chromatids40 chromatids at the beginning of meiosis would, at its completion, produce cells containing how many chromosomeschromosomes?
![Page 45: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/45.jpg)
ANSWER:ANSWER:
10 chromosomes10 chromosomes
![Page 46: MEIOSIS. MEIOSIS cell divisiongametes, half chromosomes, The form of cell division by which gametes, with half the number of chromosomes, are produced](https://reader038.vdocument.in/reader038/viewer/2022102809/56649f335503460f94c4f9cb/html5/thumbnails/46.jpg)