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 {{ANAT2341Lab1}}
 == Female Gametogenesis ==
 [[File:Chromosome- structure.jpg|thumb|Chromosome structure]]

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Created page with "{{ANAT2341Lab1}} == Female Gametogenesis == thumb|Chromosome structure In females, the total number of eggs ever to be produced are present ..."

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{{ANAT2341Lab1}}
== Female Gametogenesis ==
[[File:Chromosome- structure.jpg|thumb|Chromosome structure]]
In females, the total number of eggs ever to be produced are present in the newborn female.

# All eggs are arrested at an early stage of the first meiotic division as a primary oocyte (primordial follicle). Following purberty, during each menstrual cycle, pituitary gonadotrophin stimulates completion of '''meiosis 1''' the day before ovulation.
# In '''meiosis 1''', a diploid cell becomes 2 haploid (23 chromosomes) daughter cells, each chromosome has two chromatids. One cell becomes the secondary oocyte the other cell forms the first polar body.
# The secondary oocyte then commences '''meiosis 2''' which arrests at metaphase and will not continue without fertilization.
# At fertilization '''meiosis 2''' completes, forming a second polar body. Note that the first polar body may also undergo this process forming a third polar body.

[[File:Female_gametogenesis.jpg|600px|Female gametogenesis]]

===Female Abnormalities===
[[File:Trisomy21female.jpg|thumb|300px|Trisomy 21 female karyotype]]
Meiotic non-disjunction resulting in aneuploidy, most are embryonic lethal and not seen. The potential for genetic abnormalities [[Genetic_risk_maternal_age|increase with maternal age]].

* Autosomal chromosome aneuploidy
** '''trisomy 21''' - [[trisomy 21|Down syndrome]]
** '''trisomy 18''' - [[trisomy 18|Edwards syndrome]]
** '''trisomy 13''' - [[trisomy 13|Patau syndrome]]

* Sex chromosome aneuploidy
** monosomy X - Turner's Syndrome
** trisomy X - Triple-X syndrome
** 47 XXY - Klinefelter's Syndrome

== 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>

== Differences in Mammalian Meioses ==

{| border='0px' width=90%

|-bgcolor="lightsteelblue"
|
| '''Female Oogenesis'''
| '''Male Spermatogenesis'''
|-
| '''Meiosis initiated'''
| once in a finite population of cells
| continuously in mitotically dividing stem cell population
|-bgcolor="F5FAFF"
| '''Gametes produced'''
| 1 / meiosis
| 4 / meiosis
|-
| '''Meiosis completed'''
| delayed for months or years
| completed in days or weeks
|-bgcolor="F5FAFF"
| '''Meiosis Arrest'''
| arrest at 1st meiotic prophase
| no arrest differentiation proceed continuously
|-
| '''Chromosome Equivalence'''
| All chromosomes exhibit equivalent transcription and recombination during meiotic prophase
| Sex chromosomes excluded from recombination and transcription during first meiotic prophase
|-bgcolor="F5FAFF"
| '''Gamete Differentiation'''
| occurs while diploid (in first meiotic prophase)
| occurs while haploid (after meiosis ends)
|}

==Additional Information==
'''The information below is not part of today's Practical.'''

===Genetics===
<gallery>
File:Autosomal_dominant_inheritance.jpg|Autosomal dominant inheritance
File:Autosomal recessive inheritance.jpg|Autosomal recessive inheritance
File:X-Linked_dominant_(affected_father).jpg|X-Linked dominant (affected father)
File:X-Linked_dominant_(affected_mother).jpg|X-Linked dominant (affected mother)
File:X-Linked_recessive_(affected_father).jpg|X-Linked recessive (affected father)
File:X-Linked recessive (carrier mother).jpg|X-Linked recessive (carrier mother)
File:Mitochondrial_inheritance.jpg|Mitochondrial genome inheritance
File:Codominant inheritance.jpg|Codominant inheritance
</gallery>

{{Template:GHR Inheritance}}

==Terms==
* '''autosomal inheritance''' - some hereditary diseases are described as autosomal which means that the disease is due to a DNA error in one of the 22 pairs that are not sex chromosomes. Both boys and girls can then inherit this error. If the error is in a sex chromosome, the inheritance is said to be sex-linked.

* '''gene''' - a sequence of DNA that encodes an individual protein.

* '''genome''' - the complete genetic information in the form of DNA available to a specific species.

* '''sperm''' - See [[S#spermatozoa|spermatozoa]]. The male haploid reproductive cell, often used generically (and incorrectly) to describe these cells and the fluid of the ejaculate. Term is a shortened form of scientifically correct term [[S#spermatazoa|spermatazoa]].

* '''sperm annulus''' - (Jensen's ring; Latin, ''annulus'' = ring) A region of the mammalian sperm flagellum connecting the midpiece and the principal piece. The annulus is a septin-based structure formed from SEPT1, 4, 6, 7 and 12. Septins are polymerizing GTPases that can act as a scaffold forming hetero-oligomeric filaments required for cytokinesis and other cell cycle roles.

* '''spermatid''' - Intermediate cell in spermatozoa development, within the testis seminiferous tubule they lie in the luminal cell layer to the [[S#secondary spermatocyte|secondary spermatocyte]]. These small cells are haploid and in [[S#spermiogenesis|spermiogenesis]] change their cellular structure and shape to form [[S#spermatozoa|spermatozoa]].

:(More? [[Spermatozoa Development]] | [[Testis Development]] | [[Fertilization]] | [[2009 Lecture 2|Lecture - Cell Division/Fertilization]])

* '''spermatogenesis''' - (Greek, ''genesis'' = origin, creation, generation) The term used to describe the process of diploid spermatagonia division and differentiation to form haploid spermatazoa within the testis (male gonad). The process includes the following cellular changes: meiosis, reoorganization of DNA, reduction in DNA content, reorganization of cellular organelles, morphological changes (cell shape). The final process of change in cell shape is also called [[S#spermiogenesis|spermiogenesis]].

* '''spermiogenesis''' - (Greek, ''genesis'' = origin, creation, generation) The maturation process of the already haploid [[S#spermatid|spermatids]] into the mature [[S#spermatozoa|spermatozoa]] shape and organization. This process involves reorganization of cellular organelles ([[E#endoplasmic reticulum|endoplasmic reticulum]], [[G#golgi apparatus|Golgi apparatus]], [[M#mitochondria|mitochondria]]), cytoskeletal changes (microtubule organization) and morphological changes (cell shape, acrosome and tail formation). The process of maturation of the [[S#spermatid|spermatids]] into spermatozoa: chromatin condenses, nucleus becomes smaller, the [[G#golgi apparatus|Golgi apparatus]] is modified to form the [[A#acrosome|acrosome]], microtubules are reorganised to form the tail, mitochondria are relocated to the initial segment of the tail and the majority of cell cytoplasm is discarded.

* '''spermatogonia''' - These cells form in the embryo from the [[P#primordial germ cell|primordial germ cell]] and are located in the seminiferous tubule adjacent to the basal membrane. The cells can either divide and separate to renew the stem cell population, or they divide and stay together as a pair ([[A#Apr spermatogonia|Apr spermatogonia]]) connected by an intercellular cytoplasmic bridge to begin to differentiate and eventually form [[S#spermatazoa|spermatazoa]].

* '''spermatozoa''' - (spermatozoon, singular term) The male haploid gamete cell produced by meiosis in the testis (male gonad) seminiferous tubule. In humans, produced from puberty onwards and develop from the diploid stem cell the [[S#spermatogonia|spermatogonia]]. The developmental meiosis is called [[S#spermatogenesis|spermatogenesis]] and the final morphologiccal (shape) change is called [[S#spermeiogenesis|spermeiogenesis]]. The mature human spermatozoon formed from the [[S#spermatid|spermatid]] has a head, neck and tail and is about 60 µm long. At ejaculation these cells undergo [[C#capacitation|capacitation]] are activated and become motile.

* '''spermatozoa head''' - Following [[S#spermiogenesis|spermiogenesis]], the first region of the [[S#spermatozoa|spermatozoa]] containing the haploid nucleus and acrosome. In humans, it is a flattened structure (5 µm long by 3 µm wide) with the posterior part of nuclear membrane forming the basal plate region. The human [[S#spermatozoa|spermatozoa]] is about 60 µm long, actively motile and divided into 3 main regions ([[S#spermatozoa head|head]], [[S#spermatozoa neck|neck]] and [[S#spermatozoa tail|tail]]).

* '''spermatozoa neck''' - Following [[S#spermiogenesis|spermiogenesis]], the second region of the [[S#spermatozoa|spermatozoa]] attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail. In humans, it forms a short structure (1 µm). The human [[S#spermatozoa|spermatozoa]] is about 60 µm long, actively motile and divided into 3 main regions ([[S#spermatozoa head|head]], [[S#spermatozoa neck|neck]] and [[S#spermatozoa tail|tail]]).

* '''spermatozoa tail''' - Following [[S#spermiogenesis|spermiogenesis]], the third region of the [[S#spermatozoa|spermatozoa]] that has a ([[S#spermatozoa head|head]], [[S#spermatozoa neck|neck]] and [[S#spermatozoa tail|tail]]). The tail is also divided into 3 structural regions a middle piece, a principal piece and an end piece. In humans: the middle piece (5 µm long) is formed by [[A#axonema|axonema]] and dense fibres surrounded by mitochondria; the principal piece (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops; the final end piece (5 µm long) has an [[A#axonema|axonema]] surrounded by small amount of cytoplasm and plasma membrane.

* '''spermatogonial stem cells''' - (SSCs) The [[S#spermatagonia|spermatagonia cells]] located beside the seminiferous tubule basal membrane that either divide and separate to renew the stem cell population, or they divide and stay together as a pair ([[A#Apr spermatogonia|Apr spermatogonia]]) connected by an intercellular cytoplasmic bridge to differentiate and eventually form [[S#spermatazoa|spermatazoa]].

* '''sperm protein 56''' - A component of the spermatozoa acrosomal matrix released to the sperm surface during [[C#capacitation|capacitation]].

{{ANAT2341Lab1}}

{{Template:Glossary}}

{{Template:Footer}}

[[Category:Meiosis]] [[Category:Gametogenesis]]

ANAT2341 Lab 1 - Gametogenesis - Revision history

Z8600021: Protected "ANAT2341 Lab 1 - Gametogenesis" ([Edit=Allow only administrators] (indefinite) [Move=Allow only administrators] (indefinite))

Z8600021 at 01:08, 3 August 2014

Z8600021: Created page with "{{ANAT2341Lab1}} == Female Gametogenesis == Chromosome structure In females, the total number of eggs ever to be produced are present ..."