Meiosis

  • 407 views
Uploaded on

 

More in: Technology , Education
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
407
On Slideshare
0
From Embeds
0
Number of Embeds
1

Actions

Shares
Downloads
21
Comments
0
Likes
0

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. MeiosisReproduction of sex cells
  • 2. I. History In 1882, a scientist observed that the sex cells of roundworms contained different numbers of chromosomes in comparison to the body (somatic) cells of the individuals.
  • 3. These observations led scientists to believe that a different type of cell division occurred that reduced the number of chromosomes by half
  • 4. o In human and other eukaryotic organisms there are two types of cells1. Somatic cells or basic BODY cells that have 46 chromosomes or 23 PAIRS -Diploid cells contain a FULL SET of chromosomes
  • 5. o In human and other eukaryotic organisms there are two types of cells2. Gametes or SEX cells that have 23 chromosomes -Haploid cells have HALF the number of chromosomes Sperm Egg
  • 6. This was important because when 2 sex cells fused together during FERTILIZATION they produce a new DIPLOID cell called a ZYGOTE
  • 7. II. Human Chromosome Types:Within a diploid cell there are two different types of chromosomes 1. _AUTOSOMES (non sex chromosomes): 44 chromosomes (22 sets) -most are HOMOLOGOUS CHROMOSOMES or pairs of chromosomes from mom and dadthat are alike and carry the same genetic traits
  • 8. • Each pair have genes in the SAME location• _MALE sex chromosomes are NOT homologous
  • 9. Are the following homologous or nonhomologous?
  • 10. The other type of chromosomes are…2. SEX chromosomes: these determine the gendera. _XX – female (these are homologous)b. _XY – male(these are non homologous)
  • 11. Chromosomes can be seen during different stages of the cell cycle. A KARYOTYPE is a photograph that shows these chromosomes.
  • 12. III. The Sexual Life CycleA. MEIOSIS: DIVISION of a diploid cell toproduce SEX CELLS with 23 chromosomes
  • 13. KEY POINTS:1. _TOGETHER meiosis and fertilization represent SEXUAL reproduction2. _GAMETE cells produces are haploid sperm and egg cells3. Results in 4 genetically NON-IDENTICAL daughter cells4. Ensures GENETIC VARIABILITY by mixing of genes
  • 14. RESULT:1. Through the process of sexual reproduction PARENTS will pass genetic information onto the next generation2. The offspring will INHERIT a great variety of gene combinations
  • 15. IV. A Closer Look at Meiosis• Two rounds of cell division called MEIOSIS I and MEIOSIS IIDNA replication only occurs 1 time between the nuclear divisions to reduce the original chromosome number by half
  • 16. Draw this flow map across your paper…then add details under each squareOvary/Teste Interphase Meiosis I Meiosis II Production of Gametes
  • 17. Ovary/Teste• Site of Meiosis
  • 18. Interphase• DNA copies• (just like in Mitosis)
  • 19. P M Meiosis I A T• Nuclear division• Crossing over of homologous chromosomes• Independent assortment of chromosomes
  • 20. P M Meiosis II A T• No interphase, DNA does NOT copy• Otherwise, looks like mitosis• Nuclear division• Chromosomes separate
  • 21. Production of Gametes• 4 Haploid cells• Sperm/egg
  • 22. V. Phases of Meiosis I• To understand why haploid cells are genetically different, Meiosis I needs to be explainedA. Interphase: chromosomes copy (s-phase) (in humans, 46 chromosomes copy, making 92)
  • 23. B. During Prophase:o _HOMOLOGOUS CHROMOSOMES PAIR and CROSSOVERo Crossing over: ensures genetic variability in the offspring because of RECOMBINATION or MIXING of genetic material
  • 24. Color code your chromosomes…
  • 25. D. During Anaphase:o _INDEPENDENT ASSORTMENT occurso After metaphase, pairs of chromosomes SEPARATE and SORT randomly during cell division to produce gametes containing one chromosome of each type
  • 26. E. Telophase and Cytokinesis:• Pairs are separated into two new cells
  • 27. VI. Phases of Meiosis II:• _NO INTERPHASE occurs between two divisions, the new cells produces will have a REDUCTION in chromosome number and only have half the number of chromosomes• PMAT, cytokinesis occurs: looks like mitosis• _4 NEW cells will RESULT and will be non identical due to crossing over and random separation of chromosomes
  • 28. MEIOSIS IPMAT MEIOSIS II PMAT