Hierdie is 'n opsomming van eendheid 2: meiose graad 12. Dit bevat inligting oor graad 11 en 10 werk. Asook chromosome, seldeling, die prosesse van meiose 1 en 2, die doel van meiose en die belangrikheid daarvan. In die opsomming word daar ook tussen mitose en meiose vergelyk asook tussen die eerst...
MEIOSE:
- Die rediksiedeling waar ‘n chromosoom in elke sel gehalveer word, van ‘n diploiede na ‘n
haploiede sel
- By diere → gamete
- By plante → spore
DIE BELANGRIKHEID VAN MEIOSE:
- Voorkom dat ‘n organisme se chromosoomgetal met elke generasie verdubbel
- Die vorming van gamete
BB!
Gametogenese: proses van gameetvorming MEIOSE:
Spermatogonese: vorming van spermselle (testes) - Haploiede gamete in diere
- Haploiede spore in plante
Oögenese: vorming van ovums (ovariums)
MITOSE:
- Produseer gamte in plante
UITSONDERINGS BY PLANTE:
- Haploiede spore word tydens meiose gevorm
- By plante soos mosse en varings gee diploiede sporofietgenerasie deur meiose oorsprong aan
haploiede spore
- Haploiede spore ontkiem en gee oorsprong aan haploiede gametofietgenerasie
- Haploiede gamete word van volwasse gametofietplantjie deur mitose gevorm
- Haploiede manlike en vroulike gameet versmelt →diploiede sigoot vorm
- Diploiede sigoot ontwikkel tot diploiede sporofietgenerasie
-
GENETISE VARIASIE:
1. Oorkruising:
- Die uitruil van genetiese materiaal vir variasie
- Profase 1
2. Ewekansige rangskikking van chromosome op die ewenaar:
- Metafase 1
3. Ewekansige bevrugting:
- Watter spermsel by watter eiersel versmelt
, MEIOSE 1:
Profase 1: - Chromatiennetwerk wort korter en dikker en word as
chromosome sigbaar
- Homoloë chromosome rangskik in pare
Spoeldrade
- Bivalent vorm
- Oorkruising vind plaas (chiasma)
- Kernmembraan en kernliggaampie verdywn
- Sentrosoom verdubbel en sentriole beweeg na t/o pole
Homoloë - Spoelvesels vorm
chromosome
Metafase 1: - Homoloë chromosome rangskik hulself:
1. langs mekaar
2. ewewydig aan mekaar
3. weerskante van die ewenaar
- Spoelvesels heg aan sentromere
Anafase 1: - Spoelvesels trek saam en trek die volledige
chromosome na pole
- Homoloë pare chromosome word geskei
- Sitokinese begin
Telofase 1: - Chromosome rangskik hulself by pole
- Spoelvesels verdwyn
- Kernmembraan vorm om elke groep chromosome
vernouing - Kernliggaampie vorm
- Sitokinese is voltooi en twee dogterselle is gevorm
- Dogtersel: een chromosoom van elke homoloë paar
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