https://embryology.med.unsw.edu.au/embryology/api.php?action=feedcontributions&user=Z5060486&feedformat=atomEmbryology - User contributions [en-gb]2024-03-28T16:37:33ZUser contributionsMediaWiki 1.39.6https://embryology.med.unsw.edu.au/embryology/index.php?title=BGDA_Practical_3_-_Gametogenesis&diff=227884BGDA Practical 3 - Gametogenesis2016-05-10T06:02:51Z<p>Z5060486: </p>
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== Female Gametogenesis ==<br />
[[File:Ovary_histology_061.jpg|thumb|Oocyte and support cells in an astral follicle]]<br />
In females, the total number of eggs ever to be produced are present in the newborn female.<br />
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# 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.<br />
# 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.<br />
# The secondary oocyte then commences '''meiosis 2''' which arrests at metaphase and will not continue without fertilization.<br />
# 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.<br />
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{|<br />
| [[File:Female_gametogenesis.jpg|600px|Female gametogenesis]]<br />
| valign="bottom"|{{Meiosis movie 1}}<br />
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A mouse oocyte undergoing meiosis spindle migration followed by first polar body extrusion and MII spindle positioning.<ref name=PMID23439682><pubmed>23439682</pubmed>| [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3587830 PMC3587830] | [http://jcb.rupress.org/content/200/5/567.full J Cell Biol.]</ref><br />
* <font color=blue>'''blue'''</font> - Hoechst staining of chromosomes. <br />
* <font color=green>'''green'''</font> - UtrCH-GFP was used to label cortical changes during spindle migration. <br />
The video shows that cytoplasmic streaming continues to the MII arrest stage to maintain the oocyte set of chromosomes/MII spindle in place close to the cortex. Frames are 11 min apart, and video length is 840 min. Bar, 20 µm.<br />
|}<br />
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{|<br />
| [[File:Oogenesis and meiosis cartoon.jpg|600px]]<br />
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Meiosis and Oogenesis<ref><pubmed>22705668</pubmed>| [http://www.nature.com/nrg/journal/v13/n7/full/nrg3245.html Nat Rev Genet.]</ref><br />
|'''Meiosis''' - divided into 3 temporally distinct phases. <br />
# Prophase - after DNA replication, homologous chromosomes (shown in red and blue) undergo pairing, synapsis and recombination, and arrest at the diplotene (dictyate) stage. <br />
# Dictyate arrest - oocytes remain in meiotic arrest until the female reaches maturity and the oocyte has completed an extensive period of growth following follicle formation. <br />
# Divisions - luteinizing hormone (LH) surge that triggers ovulation also causes resumption and completion of the first meiotic division in the periovulatory oocyte. The ovulated egg is arrested at second meiotic metaphase, and anaphase onset and completion of meiosis II only occur if the egg is fertilized.<br />
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'''Oogenesis''' - complex involving 4 distinct phases. <br />
# Commitment to meiosis and meiotic initiation - occurs at {{GA}} 8–10 weeks in humans. <br />
# Follicle formation - occurs during the [[Second Trimester|second trimester]] in humans. <br />
# Oocyte growth - occurs in the sexually mature female under the control of paracrine and endocrine signals. Oocyte growth is thought to take approximately 85 days in humans and typically culminates in the ovulation of a single egg. <br />
# Fertilization - of the ovulated egg results in the completion of the second meiotic division.<br />
|}<br />
===Female Abnormalities===<br />
Meiotic non-disjunction resulting in aneuploidy, most are embryonic lethal and not seen. The most common non-lethal abnormality is [[trisomy 21|Trisomy 21 or Down syndrome]]. The potential for this and most genetic abnormalities [[Genetic_risk_maternal_age|increase with maternal age]].<br />
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{|<br />
| [[File:Trisomy21female.jpg|400px]]<br />
| [[File:Turner syndrome karyotype.jpg|400px]]<br />
|-<br />
| Trisomy 21 female karyotype<br />
| Turner's Syndrome karyotype<br />
|-<br />
|<br />
* Autosomal chromosome aneuploidy<br />
** '''trisomy 21''' - [[trisomy 21|Down syndrome]]<br />
** '''trisomy 18''' - [[trisomy 18|Edwards syndrome]]<br />
** '''trisomy 13''' - [[Trisomy_13|Patau syndrome]]<br />
|<br />
* Sex chromosome aneuploidy<br />
** monosomy X - Turner's Syndrome<br />
** trisomy X - [[Trisomy_X|Triple-X syndrome]]<br />
** 47 XXY - Klinefelter's Syndrome<br />
|}<br />
== Male Gametogenesis ==<br />
[[File:Seminiferous-tubule-HEx40.jpg|thumb|Adult seminiferous tubule showing spermatozoa developmental stages]]<br />
The histology will be covered in a separate Male Histology Practical] ([[BGDA_Practical_-_Male_Reproductive_Tract_Histology|support page]]).<br />
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<br />
[[File:Male_gametogenesis.jpg|600px]]<br />
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The above figure compares meiosis to the female (the polar bodies have been removed and labelling updated).<br />
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<gallery><br />
File:Historic-testis.jpg|Historic testis drawing<br />
File:Testis_histology_006.jpg|Immature (child) seminiferous tubule showing no spermatozoa<br />
File:Testis_histology_2.jpg|Seminiferous tubule cross-section and supporting cells<br />
File:Human-spermatozoa.jpg|Human spermatozoa<br />
</gallery><br />
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===Human Spermatozoa Development===<br />
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* Spermatogenesis process of spermatagonia mature into spermatazoa (sperm).<br />
* Continuously throughout life occurs in the seminiferous tubules in the male gonad- testis (plural testes).<br />
* At puberty spermatagonia activate and proliferate (mitosis).<br />
* about 48 days from entering meiosis until morphologically mature spermatozoa<br />
* about 64 days to complete spermatogenesis, depending reproduction time of spermatogonia<br />
* follicle stimulating hormone (FSH) - stimulates the spermatogenic epithelium<br />
* luteinizing-hormone (LH) - stimulates testosterone production by Leydig cells<br />
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===Spermiogenesis===<br />
[[File:Human_spermatozoa_acrosomal_protein_SP-10.jpg|600px]]<br />
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[[File:Human-spermatozoa_EM01.jpg|600px]]<br />
{|<br />
|-<br />
| [[File:Spermatozoa animation icon.jpg|200px|link=Development_Animation_-_Spermatozoa]]<br />
| '''Mature human spermatozoa''' <br />
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* 60 µm long, actively motile<br />
* divided into 3 main regions (head, neck and tail)<br />
* head - (flattened, 5 µm long by 3 µm wide) the nucleus and acrosome. Posterior part of nuclear membrane forms the basal plate.<br />
* neck - (1 µm) attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail.<br />
* tail - 3 parts a middle piece, principal piece and end piece<br />
** middle piece - (5 µm long) [[A#axonema|axonema]] and dense fibres surrounded by mitochondria<br />
** principal piece - (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops<br />
** end piece - (5 µm long) [[A#axonema|axonema]] surrounded by small amount of cytoplasm and plasma membrane<br />
|-<br />
|}<br />
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:'''Links:''' [[Spermatozoa Development]] | [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mboc4&part=A3729 MBoC - Sperm] | [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mboc4&part=A3729&rendertype=figure&id=A3735 MBoC - Highly simplified drawing of a cross-section of a seminiferous tubule in a mammalian testis] | [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mboc4&part=A3729&rendertype=figure&id=A3736 MBoC - Cytoplasmic bridges in developing sperm cells and their precursors]<br />
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===Puberty===<br />
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* In humans at puberty, hormonal and morphological changes occur within the gonad and other systems (secondary sex characteristics). <br />
* Within the testis the immature Sertoli cells cease to proliferate and differentiate. <br />
* Spermatogonium (plural, spermatogonia) proliferate and spermatogenesis begins.<br />
* It takes about 70 days for cells to mature from the diploid spermatogonium to a primary spermatocyte. <br />
* This maturation occurs in waves along the seminiferous tubules.<br />
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===Ejaculate===<br />
[[File:Azoospermia.jpg|thumb|Azoospermia - Non-obstructive azoospermia (NOA) and Obstructive azoospermia (OA)]]<br />
*release of spermatozoa and accessory gland secretions from the male genital tract (3.5 ml)<br />
* 200-600 million sperm, by volume less than 10 % spermatozoa<br />
* Accessory Gland secretions - 60 % seminal vesicle, 30 % prostate and 10 % bulbourethral<br />
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===Male Abnormalities===<br />
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* '''Oligospermia''' - (Low Sperm Count) less than 20 million sperm after 72 hour abstinence from sex<br />
* '''Azoospermia''' - (Absent Sperm) blockage of duct network<br />
* '''Immotile Cilia Syndrome''' - lack of sperm motility<br />
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== Differences in Mammalian Meioses ==<br />
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{| border='0px' width=90%<br />
<br />
|-bgcolor="lightsteelblue"<br />
|<br />
| '''Female Oogenesis'''<br />
| '''Male Spermatogenesis'''<br />
|-<br />
| '''Meiosis initiated'''<br />
| once in a finite population of cells <br />
| continuously in mitotically dividing stem cell population<br />
|-bgcolor="F5FAFF" <br />
| '''Gametes produced'''<br />
| 1 / meiosis <br />
| 4 / meiosis<br />
|-<br />
| '''Meiosis completed'''<br />
| delayed for months or years<br />
| completed in days or weeks<br />
|-bgcolor="F5FAFF" <br />
| '''Meiosis Arrest'''<br />
| arrest at 1st meiotic prophase<br />
| no arrest differentiation proceed continuously<br />
|-<br />
| '''Chromosome Equivalence'''<br />
| All chromosomes exhibit equivalent transcription and recombination during meiotic prophase<br />
| Sex chromosomes excluded from recombination and transcription during first meiotic prophase<br />
|-bgcolor="F5FAFF" <br />
| '''Gamete Differentiation'''<br />
| occurs while diploid (in first meiotic prophase) <br />
| occurs while haploid (after meiosis ends) <br />
|}<br />
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==Additional Information==<br />
{{Med Prac additional Information}}<br />
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[[File:Chromosome- structure.jpg|thumb|Chromosome structure]]<br />
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* [[BGDA_Practical_-_Male_Reproductive_Tract_Histology|Male Histology]] - covered in another practical class.<br />
* [[#Genetics|Genetic Information]] - covered elsewhere in your course.<br />
* [[#Mitosis and Meiosis|Mitosis and Meiosis]] - Cell Biology of mitosis and meiosis covered also in Foundations.<br />
===Male Histology===<br />
This will be covered in detail in a separate Histology practical class. [http://vslides.unsw.edu.au/VirtualSlideV2.nsf/id/37AFC0 Virtual Slides]<br />
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From today's class you should have a basic understanding of seminiferous tubule structure in relation to spermatozoa development.<br />
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===Genetics===<br />
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Where genes are located and how they are inherited relate to the chromosome that the gene is located upon, the parental origin of the gene and the dominant/recessive nature of the gene.<br />
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<gallery><br />
File:Autosomal_dominant_inheritance.jpg|Autosomal dominant inheritance<br />
File:Autosomal recessive inheritance.jpg|Autosomal recessive inheritance<br />
File:X-Linked_dominant_(affected_father).jpg|X-Linked dominant (affected father)<br />
File:X-Linked_dominant_(affected_mother).jpg|X-Linked dominant (affected mother)<br />
File:X-Linked_recessive_(affected_father).jpg|X-Linked recessive (affected father)<br />
File:X-Linked recessive (carrier mother).jpg|X-Linked recessive (carrier mother)<br />
File:Mitochondrial_inheritance.jpg|Mitochondrial genome inheritance<br />
File:Codominant inheritance.jpg|Codominant inheritance<br />
</gallery><br />
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{{GHR Inheritance}}<br />
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===Mitosis and Meiosis===<br />
[[File:Mitosis_and_meiosis.jpg|600px]]<br />
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:'''Links:''' [[Cell_Division_-_Mitosis|Mitosis]] | [[Cell_Division_-_Meiosis|Meiosis]]<br />
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==Terms==<br />
* '''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.<br />
* '''cascade testing''' - Clinical genetic term for the testing of genetic relatives for a mutation that has been identified in the first affected family member. [[Abnormal Development - Genetic]]<br />
* '''gene''' - a sequence of DNA that encodes an individual protein.<br />
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* '''genome''' - the complete genetic information in the form of DNA available to a specific species.<br />
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* '''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]]. <br />
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* '''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. <br />
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* '''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]].<br />
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:(More? [[Spermatozoa Development]] | [[Testis Development]] | [[Fertilization]] | [[Lecture - Fertilization]])<br />
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* '''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]]. <br />
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* '''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.<br />
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* '''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]]. <br />
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* '''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.<br />
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* '''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]]).<br />
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* '''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]]).<br />
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* '''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.<br />
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* '''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]]. <br />
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* '''sperm protein 56''' - A component of the spermatozoa acrosomal matrix released to the sperm surface during [[C#capacitation|capacitation]].<br />
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[[Category:Meiosis]] [[Category:Gametogenesis]]</div>Z5060486