Cell Division - Meiosis: Difference between revisions
From Embryology
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==Some Recent Findings== | ==Some Recent Findings== | ||
==Mitosis and Meiosis== | |||
[[Image:Mitosis meiosis1.jpg]] | |||
Progeny | |||
Mitosis 2 Daughter cells identical to parent (diploid) | |||
Meiosis Germ cell division (haploid) | |||
* Reductive division | |||
* Generates haploid gametes (egg, sperm) | |||
* Each genetically distinct from parent | |||
* Genetic recombination (prophase 1) | |||
** Exchanges portions of chromosomes maternal/paternal homologous pairs | |||
* Independent assortment of paternal chromosomes (meiosis 1) | |||
Cell Birth - Mitosis and Meiosis 1st cell division- Meiosis | |||
Homologous chromosomes pairing unique to meiosis | |||
* Each chromosome duplicated and exists as attached sister chromatids before pairing occurs | |||
* Genetic Recombination shown by chromosomes part red and part black | |||
** chromosome pairing in meiosis involves crossing-over between homologous chromosomes | |||
(For clarity only 1 pair of homologous chromosomes shown) | |||
===Comparison of Meiosis/Mitosis=== | |||
* After DNA replication 2 nuclear (and cell) divisions required to produce haploid gametes | |||
* Each diploid cell in meiosis produces 4 haploid cells (sperm) 1 haploid cell (egg) | |||
* Each diploid cell mitosis produces 2 diploid cells | |||
==Abnormalities== | |||
===Meiotic Nondisjunction=== | |||
* Occurs when homologues fail to separate during meiotic division I or II | |||
* Down Syndrome | |||
* Caused by an extra copy of chromosome 21 | |||
[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A3575&rendertype=figure&id=A3577 Nondisjunction] | |||
===Chromosomal Translocations=== | |||
* Philadelphia chromosome | |||
* Chronic myelogenous leukemia | |||
** Piece of Chr9 exchanged with Chr22 Generates truncated abl | |||
Overstimulates cell production | |||
===Meiosis Sex Differences=== | |||
'''Female''' (oogenesis) | |||
* Meiosis initiated once in a finite population of cells | |||
* 1 gamete produced / meiosis | |||
* Completion of meiosis delayed for months or years | |||
* Meiosis arrested at 1st meiotic prophase and reinitiated in a smaller population of cells | |||
* Differentiation of gamete occurs while diploid in first meiotic prophase | |||
* All chromosomes exhibit equivalent transcription and recombination during meiotic prophase | |||
'''Male''' (spermatogenesis) | |||
* Meiosis initiated continuously in a mitotically dividing stem cell population | |||
* 4 gametes produced / meiosis | |||
* Meiosis completed in days or weeks | |||
* Meiosis and differentiation proceed continuously without cell cycle arrest | |||
* Differentiation of gamete occurs while haploid after meiosis ends | |||
Sex chromosomes excluded from recombination and transcription during first meiotic prophase | |||
==References== | ==References== | ||
Revision as of 17:09, 14 July 2010
Introduction
Some Recent Findings
Mitosis and Meiosis
Progeny
Mitosis 2 Daughter cells identical to parent (diploid)
Meiosis Germ cell division (haploid)
- Reductive division
- Generates haploid gametes (egg, sperm)
- Each genetically distinct from parent
- Genetic recombination (prophase 1)
- Exchanges portions of chromosomes maternal/paternal homologous pairs
- Independent assortment of paternal chromosomes (meiosis 1)
Cell Birth - Mitosis and Meiosis 1st cell division- Meiosis
Homologous chromosomes pairing unique to meiosis
- Each chromosome duplicated and exists as attached sister chromatids before pairing occurs
- Genetic Recombination shown by chromosomes part red and part black
- chromosome pairing in meiosis involves crossing-over between homologous chromosomes
(For clarity only 1 pair of homologous chromosomes shown)
Comparison of Meiosis/Mitosis
- After DNA replication 2 nuclear (and cell) divisions required to produce haploid gametes
- Each diploid cell in meiosis produces 4 haploid cells (sperm) 1 haploid cell (egg)
- Each diploid cell mitosis produces 2 diploid cells
Abnormalities
Meiotic Nondisjunction
- Occurs when homologues fail to separate during meiotic division I or II
- Down Syndrome
- Caused by an extra copy of chromosome 21
Chromosomal Translocations
- Philadelphia chromosome
- Chronic myelogenous leukemia
- Piece of Chr9 exchanged with Chr22 Generates truncated abl
Overstimulates cell production
Meiosis Sex Differences
Female (oogenesis)
- Meiosis initiated once in a finite population of cells
- 1 gamete produced / meiosis
- Completion of meiosis delayed for months or years
- Meiosis arrested at 1st meiotic prophase and reinitiated in a smaller population of cells
- Differentiation of gamete occurs while diploid in first meiotic prophase
- All chromosomes exhibit equivalent transcription and recombination during meiotic prophase
Male (spermatogenesis)
- Meiosis initiated continuously in a mitotically dividing stem cell population
- 4 gametes produced / meiosis
- Meiosis completed in days or weeks
- Meiosis and differentiation proceed continuously without cell cycle arrest
- Differentiation of gamete occurs while haploid after meiosis ends
Sex chromosomes excluded from recombination and transcription during first meiotic prophase
References
Reviews
Articles
Search Pubmed
Search Pubmed: meiosis
Additional Images
Cite this page: Hill, M.A. (2024, April 23) Embryology Cell Division - Meiosis. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Cell_Division_-_Meiosis
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
