Meiosis n mitosis in cells (Microbiology).ppt

It describes the meiosis and mitosis

1. Mitosis & Meiosis

2. Mitosis Review
Cell makes a copy of itself
1) Copy its DNA (part of a chromosome).
2) Copies are separated & sorted into two sides of the cell.
3) The cell then splits in two.
4) Part of each parent is carried to the two new cells.
5) Two EXACT daughter cells (same number of chromosomes)
Examples: skin, bones, internal organs

3. Meiosis – Sexual Reproduction – Sexual Reproduction
•Cell divisionCell division that forms gametes (egg and sperm
cells)
•GametesGametes have halfhalf the # of chromosomeschromosomes.
•Two divisionsTwo divisions (meiosis I meiosis I and meiosis IImeiosis II).
•Part of each parent is carried to the four new cells.
•MeiosisMeiosis is similar to mitosismitosis with some
chromosomal differences.

4. Mitosis: Meiosis:

Each resulting cell still has chromosomes from Mom & DadEach resulting cell still has chromosomes from Mom & Dad

5. Tips
•MITosis takes one cell and Makes It Two
•Meiosis has to do with sex
•From the cell’s point of view:
– mITosis results in Identical Twins
CELLS
– mEioSis results in Egg and Sperm

6. Homologous ChromosomesHomologous Chromosomes
•Pair of chromosomeschromosomes (maternalmaternal and paternalpaternal) that are
similar in shape and size.
•Homologous pairs carry genes controlling the same
inherited traits.
•Humans have 23 pairs of homologous chromosomes.homologous chromosomes.
a.22 pairs of autosomesautosomes
b.1 pair of sex chromosomessex chromosomes

7. Homologous chromosomes
sister chromatids
paternal
sister chromatids
maternal
Tetrad

8. Homologous ChromosomesHomologous Chromosomes

PaternalMaternal
eye color
locus
eye color
locus
hair color
locus
hair color
locus

9. Humans have 23 Sets of Homologous Chromosomes
Each Homologous set is made up of 2 Homologues.
Homologue
Homologue

10. AutosomesAutosomes
(The Autosomes code for most of the offspring’s traits)(The Autosomes code for most of the offspring’s traits)
In Humans the
“Autosomes”
are sets 1 - 22

11. Sex ChromosomesSex Chromosomes
The Sex Chromosomes code for the sex of the offspring.The Sex Chromosomes code for the sex of the offspring.
Two “X” chromosomes = Two “X” chromosomes = femalefemale..
One “X” chromosome and one “Y” chromosome = One “X” chromosome and one “Y” chromosome = malemale..
XX chromosome - female XY chromosome - male
In Humans the
“Sex
Chromosomes”
are the 23
rd
set

12. Cell Division in Sex Cells
•Interphase I
•Meiosis I and Meiosis 2
•Similar to Mitosis EXCEPT changes in
chromosomes

13. 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.

14. 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

15. Prophase IProphase I


centrioles
spindle fiber
TETRAD

16. Prophase IProphase I
•HHomologous chromosomesomologous chromosomes come
together to form a tetradtetrad.
•TetradTetrad is two chromosomeschromosomes or
four chromatidschromatids (sister and
nonsister chromatids).

17. Homologous chromosomes
sister chromatids
paternal
sister chromatids
maternal
Tetrad

18. Prophase 1 – Crossing OverProphase 1 – Crossing Over
•Crossing overCrossing over: segments of nonsister
chromatidschromatids break and reattach to the other
chromatidchromatid.
•Crossing over Crossing over causescauses variation variation

19. Crossing Over - variation Crossing Over - variation


nonsister chromatids
chiasmata: site
of crossing over
variation
Tetrad

20. Metaphase IMetaphase I
•TetradsTetrads align on the in center of cell on spindle
•INDEPENDENT ASSORTMENT OCCURS:INDEPENDENT ASSORTMENT OCCURS:
1. Orientation of homologous pair to poles is random.
2. Variation
OR

21. Anaphase IAnaphase I
•Homologous chromosomes Homologous chromosomes separate and
move towards the poles.
•Sister chromatids Sister chromatids remain attached at their
centromerescentromeres.

22. Telophase ITelophase I•Each pole now has haploidhaploid set of
chromosomeschromosomes.
•CytokinesisCytokinesis occurs and two haploid daughter
cells are formed.

23. Meiosis IIMeiosis II
•No interphase II No interphase II
•Remember:Remember: Meiosis II Meiosis II is similar to mitosismitosis

24. Prophase IIProphase II
•same as prophaseprophase in mitosismitosis

25. Metaphase IIMetaphase II
•same as metaphasemetaphase in mitosismitosis

26. Anaphase IIAnaphase II
•same as anaphaseanaphase in mitosismitosis
•sister chromatids separatesister chromatids separate

27. Telophase IITelophase II•Four haploid daughter cells producedFour haploid daughter cells produced
gametes = sperm or egggametes = sperm or egg

28. 2n
diploid
n haploid
n haploid

29. SpermatogenesisSpermatogenesis
2n=46
human
sex cell
diploid (2n)
n=23
n=23
meiosis I
n=23
n=23
n=23
n=23
sperm
haploid (n)
meiosis II

30. Oogenesis

31. FertilizationFertilization
•The fusion of a spermsperm and eggegg to form a zygotezygote.
•A zygote is a fertilized egg
n=23
egg
sperm
n=23
2n=46
zygote

32. 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 ofWhat are the three sexual sources of
genetic variation? genetic variation?

33. Answer:Answer:
1. crossing over (prophase I)1. crossing over (prophase I)
2. independent assortment (metaphase I)2. independent assortment (metaphase I)
3. random fertilization3. random fertilization
Remember: variation is good!

34. 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?

35. Answer:Answer:
•10 chromosomes (haploid)10 chromosomes (haploid)

36. Question:Question:
•A cell containing 40 chromatids40 chromatids at the
beginning of meiosis would, at its completion,
produce cells containing how many
chromosomeschromosomes?

37. Answer:Answer:
•10 chromosomes10 chromosomes

38. •Meiosis animation:
http://www.youtube.com/watch?v=D1_-mQS_
FZ0&NR=1