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How it develops and progresses.
Содержание
- 1. How it develops and progresses.
- 2. A few words before we start…..Haploid: half
- 3. Cell Reproductionis either sexual or asexual
- 4. Asexual Reproduction (one parent)Binary Fission-Vegetative Propagation Regeneration Advantages?Disadvantages?
- 5. Asexual reproductionAdvantages:Doesn’t require a mateTakes less timeDisadvantages:All offspring are the same (genetically)
- 6. Sexual Reproduction2 “parents” or 2 sets of DNAExamples: humans, plants, dogs
- 7. AdvantagesDIVERSITY!!!!!!!!!!Offspring are genetically different from parents.Disadvantages?Need a mateTakes longerSexual reproduction
- 8. MeiosisSexual Reproduction (two parents)
- 9. Why Meiosis?Meiosis - The production of gametes
- 10. Слайд 10
- 11. InterphaseCell growthDNA replication ? sister chromatids held together by centromere
- 12. Prophase IThe chromosomes coil up and a
- 13. Prophase I – crossing overCrossing over occurs
- 14. During prophase of meiosis I, homologous pairs
- 15. CROSSINGOVERCrossing over produces recombinant chromosomes, which combine
- 16. Crossing OverHomologous chromosomes line up during meiosisParts of maternal and paternal chromosomes migrate
- 17. Слайд 17
- 18. Metaphase IThe spindle fibers pull the tetrads
- 19. Anaphase IHomologous chromosomes separate and move to opposite ends of the cell.
- 20. Telophase IThe spindle is broken down, the
- 21. Remember mitosis?Meiosis II looks just like mitosis except there is no DNA replication during interphase
- 22. Prophase IIA spindle forms in each of
- 23. Metaphase II.Sister chromatids, are pulled to the
- 24. Anaphase IIThe sister chromatids separate and move to opposite poles.
- 25. Telophase IIFinally nuclei reform, the spindles breakdown,
- 26. Слайд 26
- 27. Why meiosis is importantForms gametes for sexual
- 28. Fertilization462323
- 29. Sexual reproductionMeiosisMeiosisSperm CellEgg CellHaploid gametes(n=23)FertilizationDiploid zygote(2n=46)Mitosis and DevelopmentMulticellulardiploid adults(2n=46)
- 30. Mitosis vs. Meiosis √√√√√√
- 31. Mitosis vs. Meiosis√√√√
- 32. Скачать презентанцию
A few words before we start…..Haploid: half of a full set (only 1 set of DNA)Diploid: full set (1 set from each parent (2 sets)
Слайды и текст этой презентации
Слайд 1Describe the phases of meiosis and the mechanisms of recombination
of genetic material during meiosis
Слайд 2A few words before we start…..
Haploid: half of a full
set (only 1 set of DNA)
Diploid: full set
(1 set fromeach parent (2 sets)
Слайд 4Asexual Reproduction
(one parent)
Binary Fission-
Vegetative Propagation
Regeneration
Advantages?
Disadvantages?
Слайд 5Asexual reproduction
Advantages:
Doesn’t require a mate
Takes less time
Disadvantages:
All offspring are the
same (genetically)
Слайд 7Advantages
DIVERSITY!!!!!!!!!!
Offspring are genetically different from parents.
Disadvantages?
Need a mate
Takes longer
Sexual reproduction
Слайд 12Prophase I
The chromosomes coil up and a spindle forms.
Homologous chromosomes
line up with each other gene by gene along their
length, to form a four-part structure called a tetrad.
Слайд 13Prophase I – crossing over
Crossing over occurs between homologous chromosomes
? new genetic combinations that are different from the parent.
Слайд 14During prophase of meiosis I, homologous pairs of chromosomes form
bivalents (meaning they pair up closely)
Chromatids twist around each other.
The point where they join are called chiasmataFragments of non-sister chromatids swap over and so genes are exchanged
1. CROSS - OVER
Слайд 15CROSSINGOVER
Crossing over produces recombinant chromosomes, which combine genes inherited from
each parent.
Crossing over begins very early in prophase I, as
homologous chromosomes pair up gene by gene.In crossing over, homologous portions of two nonsister chromatids trade places.
Crossing over contributes to genetic variation by combining DNA from two parents into a single chromosome.
Слайд 16Crossing Over
Homologous chromosomes line up during meiosis
Parts of maternal and
paternal chromosomes migrate
Слайд 18Metaphase I
The spindle fibers pull the tetrads into the middle,
or equator of the cell.
There is no rule to who
is on left or right side ? independent assortment.
Слайд 20Telophase I
The spindle is broken down, the chromosomes uncoil slightly,
and the cytoplasm divides to yield two new cells.
Each cell
has half the DNA as the original cell because it has only one chromosome from each homologous pair. ? Haploid
Слайд 21Remember mitosis?
Meiosis II looks just like mitosis except there is
no DNA replication during interphase
Слайд 22Prophase II
A spindle forms in each of the two new
cells and the spindle fibers attach to the chromosomes.
Слайд 23Metaphase II.
Sister chromatids, are pulled to the center of the
cell and line up randomly at the equator.
Слайд 25Telophase II
Finally nuclei reform, the spindles breakdown, and the cytoplasm
divides.
Four haploid cells have been formed from one diploid cell
All
are genetically different from each other and from the parent cell.
Слайд 27Why meiosis is important
Forms gametes for sexual reproduction
Crossing over and
independent assortment ? different genetic combinations. ? diversity!!!
Слайд 29Sexual reproduction
Meiosis
Meiosis
Sperm Cell
Egg Cell
Haploid gametes
(n=23)
Fertilization
Diploid zygote
(2n=46)
Mitosis and Development
Multicellular
diploid adults
(2n=46)
