Your SlideShare is downloading. ×
Cell Division 2
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Cell Division 2

3,562
views

Published on

Published in: Technology, Education

2 Comments
1 Like
Statistics
Notes
No Downloads
Views
Total Views
3,562
On Slideshare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
292
Comments
2
Likes
1
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. Edited by Hasimah Azit
  • 2.
    • The form of cell division by which gametes, with half the number of chromosomes, are produced.
    • Diploid (2n)  haploid (n)
    • Meiosis is sexual reproduction.
    • Two divisions ( meiosis I and meiosis II ).
  • 3.
    • Sex cells divide to produce gametes (sperm or egg) .
    • Gametes have half the # of chromosomes .
    • Occurs only in gonads (testes or ovaries).
    • Male: spermatogenesis
    • Female: oogenesis
    • Meiosis is similar to mitosis with some chromosomal differences.
  • 4. 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
  • 5.
    • Similar to mitosis interphase.
    • Chromosomes replicate (S phase).
    • Each duplicated chromosome consist of two identical sister chromatids attached at their centromeres .
    • Centriole pairs also replicate.
  • 6.
    • Nucleus and nucleolus visible.
    nuclear membrane nucleolus cell membrane chromatin
  • 7.
    • Cell division that reduces the chromosome number by one-half.
    • four phases :
    • a. prophase I
    • b. metaphase I
    • c. anaphase I
    • d. telophase I
  • 8.
    • Longest and most complex phase (90%).
    • Chromosomes condense.
    • Synapsis occurs: homologous chromosomes come together to form a tetrad .
    • Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids) .
  • 9. Homologous chromosomes sister chromatids sister chromatids Tetrad
  • 10.
    • Pair of chromosomes ( maternal and paternal ) that are similar in shape and size.
    • Homologous pairs (tetrads) carry genes controlling the same inherited traits.
    • Each locus (position of a gene) is in the same position on homologues.
    • Humans have 23 pairs of homologous chromosomes.
    • a. 22 pairs of autosomes
    • b. 01 pair of sex chromosomes
  • 11. Paternal Maternal eye color locus eye color locus hair color locus hair color locus
  • 12.
    • Crossing over (variation) may occur between nonsister chromatids at the chiasmata .
    • Crossing over : segments of nonsister chromatids break and reattach to the other chromatid .
    • Chiasmata (chiasma) are the sites of crossing over .
  • 13. variation nonsister chromatids chiasmata: site of crossing over Tetrad
  • 14. XX chromosome - female XY chromosome - male
  • 15. centrioles spindle fiber aster fibers
  • 16.
    • Shortest phase
    • Tetrads align on the metaphase plate .
    • INDEPENDENT ASSORTMENT OCCURS:
    • 1. Orientation of homologous pair to poles is random.
    • 2. Variation
    • 3. Formula: 2 n
    • Example: 2n = 4
    • then n = 2
    • thus 2 2 = 4 combinations
  • 17. metaphase plate OR metaphase plate
  • 18.
    • Homologous chromosomes separate and move towards the poles.
    • Sister chromatids remain attached at their centromeres .
  • 19.  
  • 20.
    • Each pole now has haploid set of chromosomes .
    • Cytokinesis occurs and two haploid daughter cells are formed.
  • 21.  
  • 22.
    • No interphase II
    • (or very short - no more DNA replication )
    • Remember: Meiosis II is similar to mitosis
  • 23.
    • same as prophase in mitosis
  • 24.
    • same as metaphase in mitosis
    metaphase plate metaphase plate
  • 25.
    • same as anaphase in mitosis
    • sister chromatids separate
  • 26.
    • Same as telophase in mitosis .
    • Nuclei form.
    • Cytokinesis occurs.
    • Remember: four haploid daughter cells produced.
    • gametes = sperm or egg
  • 27.  
  • 28. 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
  • 29. MEIOSIS
  • 30.  
  • 31.
    • Important to population as the raw material for natural selection .
    • Question:
    • What are the three sexual sources of
    • genetic variation?
  • 32.
    • 1. crossing over (prophase I)
    • 2. independent assortment (metaphase I)
    • 3. random fertilization
    • Remember: variation is good!
  • 33.
    • The fusion of a sperm and egg to form a zygote .
    • A zygote is a fertilized egg
    n=23 egg sperm n=23 2n=46 zygote
  • 34.
    • mitosis
    • meiosis
  • 35.  
  • 36.  

×