Talk:BGDA Practical 3 - Gametogenesis: Difference between revisions
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[[Media:BGD2010-Embryo Lab 120510-304.mp3|listen Part 4]] | [[:File:BGD2010-Embryo Lab 120510-304.mp3|download]] (1.2 Mb MP3 9:29) | [[Media:BGD2010-Embryo Lab 120510-304.mp3|listen Part 4]] | [[:File:BGD2010-Embryo Lab 120510-304.mp3|download]] (1.2 Mb MP3 9:29) | ||
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==Meiosis== | |||
[[File:Mitosis and meiosis.jpg|600px]] | |||
A diagram comparing [[Cell Division - Mitosis|mitosis]] and [[Cell Division - Meiosis|meiosis]]. | |||
==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 | |||
== Male Gametogenesis == | |||
In males, sperm continues to be generated throughout life from a stem cell population in the testis. Spermatozoa maturation involves two processes meiosis and spermiogenesis | |||
[[File:Male_gametogenesis.jpg|600px]] | |||
The above figure compares meiosis to the female (the polar bodies have been removed and labelling updated). | |||
<gallery> | |||
File:Historic-testis.jpg|Historic testis drawing | |||
File:Seminiferous-tubule-HEx40.jpg|Adult Seminiferous tubule showing spermatozoa developmental stages | |||
File:Testis_histology_2.jpg|Seminiferous tubule cross-section and supporting cells | |||
File:Human-spermatozoa.jpg|Human spermatozoa | |||
</gallery> | |||
===Human Spermatozoa Development=== | |||
* Spermatogenesis process of spermatagonia mature into spermatazoa (sperm). | |||
* Continuously throughout life occurs in the seminiferous tubules in the male gonad- testis (plural testes). | |||
* At puberty spermatagonia activate and proliferate (mitosis). | |||
* about 48 days from entering meiosis until morphologically mature spermatozoa | |||
* about 64 days to complete spermatogenesis, depending reproduction time of spermatogonia | |||
* follicle stimulating hormone (FSH) - stimulates the spermatogenic epithelium | |||
* luteinizing-hormone (LH) - stimulates testosterone production by Leydig cells | |||
[[File:Human-spermatozoa_EM01.jpg|600px]] | |||
{| | |||
|- | |||
| [[File:Spermatozoa animation icon.jpg|200px|link=Development_Animation_-_Spermatozoa]] | |||
| '''Mature human spermatozoa''' | |||
* 60 µm long, actively motile | |||
* divided into 3 main regions (head, neck and tail) | |||
* head - (flattened, 5 µm long by 3 µm wide) the nucleus and acrosome. Posterior part of nuclear membrane forms the basal plate. | |||
* neck - (1 µm) attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail. | |||
* tail - 3 parts a middle piece, principal piece and end piece | |||
** middle piece - (5 µm long) [[A#axonema|axonema]] and dense fibres surrounded by mitochondria | |||
** principal piece - (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops | |||
** end piece - (5 µm long) [[A#axonema|axonema]] surrounded by small amount of cytoplasm and plasma membrane | |||
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Latest revision as of 14:48, 9 May 2011
2010 Practical Audio
BGD Cycle A 2010 Audio - Dr Mark Hill Monday 12th May 2010 12-2pm G2G4.
listen Part 4 | download (1.2 Mb MP3 9:29) |
Meiosis
A diagram comparing mitosis and meiosis.
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
Male Gametogenesis
In males, sperm continues to be generated throughout life from a stem cell population in the testis. Spermatozoa maturation involves two processes meiosis and spermiogenesis
The above figure compares meiosis to the female (the polar bodies have been removed and labelling updated).
Human Spermatozoa Development
- Spermatogenesis process of spermatagonia mature into spermatazoa (sperm).
- Continuously throughout life occurs in the seminiferous tubules in the male gonad- testis (plural testes).
- At puberty spermatagonia activate and proliferate (mitosis).
- about 48 days from entering meiosis until morphologically mature spermatozoa
- about 64 days to complete spermatogenesis, depending reproduction time of spermatogonia
- follicle stimulating hormone (FSH) - stimulates the spermatogenic epithelium
- luteinizing-hormone (LH) - stimulates testosterone production by Leydig cells