লিঙ্গ নির্ধারণ ব্যবস্থা: সংশোধিত সংস্করণের মধ্যে পার্থক্য

উইকিপিডিয়া, মুক্ত বিশ্বকোষ থেকে
ইতিহাস ব্রাউজ করুন
← পূর্বের পার্থক্যপরবর্তী পার্থক্য →
বিষয়বস্তু বিয়োগ হয়েছে বিষয়বস্তু যোগ হয়েছে
দৃশ্যমানউইকিপাঠ্য
সম্পাদনা সারাংশ নেই
ট্যাগ: মোবাইল সম্পাদনা মোবাইল ওয়েব সম্পাদনা উচ্চতর মোবাইল সম্পাদনা
সম্পাদনা সারাংশ নেই
ট্যাগ: মোবাইল সম্পাদনা মোবাইল ওয়েব সম্পাদনা উচ্চতর মোবাইল সম্পাদনা
৯ নং লাইন: ৯ নং লাইন:
কিছু প্রজাতি যেমন বিভিন্ন উদ্ভিদ এবং মাছের একটি নির্দিষ্ট লিঙ্গ থাকে না এবং পরিবর্তে জীবনচক্র হয় এবং সম্পর্কিত জীবনের পর্যায়ে তারা জিনগত সূত্রের ভিত্তিতে লিঙ্গ পরিবর্তন করে। এটি মৌসুম এবং তাপমাত্রার মতো পরিবেশগত কারণগুলির কারণে হতে পারে। ভ্রূণের যৌন-নির্ধারণীকরণ ব্যবস্থায় পরিবর্তনের কারণে মানব ভ্রূণের যৌনাঙ্গে কখনও কখনও অস্বাভাবিকতা দেখা দিতে পারে ফলস্বরূপ ভ্রূণ [[আন্তঃআকৃতি]]র হয়ে যায়।
কিছু প্রজাতি যেমন বিভিন্ন উদ্ভিদ এবং মাছের একটি নির্দিষ্ট লিঙ্গ থাকে না এবং পরিবর্তে জীবনচক্র হয় এবং সম্পর্কিত জীবনের পর্যায়ে তারা জিনগত সূত্রের ভিত্তিতে লিঙ্গ পরিবর্তন করে। এটি মৌসুম এবং তাপমাত্রার মতো পরিবেশগত কারণগুলির কারণে হতে পারে। ভ্রূণের যৌন-নির্ধারণীকরণ ব্যবস্থায় পরিবর্তনের কারণে মানব ভ্রূণের যৌনাঙ্গে কখনও কখনও অস্বাভাবিকতা দেখা দিতে পারে ফলস্বরূপ ভ্রূণ [[আন্তঃআকৃতি]]র হয়ে যায়।
== আবিষ্কার ==
== আবিষ্কার ==
১৯০৩ সালে আমেরিকান জিনতত্ত্ববিদ [[নেটটি স্টিভেনস]] দ্বারা [[খাবারের কীট]] এর লিঙ্গ নির্ধারণ আবিষ্কার হয়েছিলো।<ref>{{Cite web|url=https://www.nature.com/scitable/topicpage/nettie-stevens-a-discoverer-of-sex-chromosomes-6580266|title=Nettie Stevens: A Discoverer of Sex Chromosomes {{!}} Learn Science at Scitable|website=www.nature.com|language=en|access-date=2018-06-07}}</ref><ref>{{Cite journal|last=Ogilvie|first=Marilyn Bailey|last2=Choquette|first2=Clifford J.|date=1981|title=Nettie Maria Stevens (1861-1912): Her Life and Contributions to Cytogenetics|jstor=986332|journal=Proceedings of the American Philosophical Society|volume=125|issue=4|pages=292–311|pmid=11620765}}</ref><ref>{{Cite web|url=https://embryo.asu.edu/pages/nettie-maria-stevens-1861-1912|title=Nettie Maria Stevens (1861-1912) {{!}} The Embryo Project Encyclopedia|website=embryo.asu.edu|language=en|access-date=2018-06-07}}</ref>
১৯০৩ সালে আমেরিকান জিনতত্ত্ববিদ [[নেটটি স্টিভেনস]] দ্বারা [[খাবারের কীট]] এর লিঙ্গ নির্ধারণ ব্যবস্থা আবিষ্কার হয়েছিলো।<ref>{{Cite web|url=https://www.nature.com/scitable/topicpage/nettie-stevens-a-discoverer-of-sex-chromosomes-6580266|title=Nettie Stevens: A Discoverer of Sex Chromosomes {{!}} Learn Science at Scitable|website=www.nature.com|language=en|access-date=2018-06-07}}</ref><ref>{{Cite journal|last=Ogilvie|first=Marilyn Bailey|last2=Choquette|first2=Clifford J.|date=1981|title=Nettie Maria Stevens (1861-1912): Her Life and Contributions to Cytogenetics|jstor=986332|journal=Proceedings of the American Philosophical Society|volume=125|issue=4|pages=292–311|pmid=11620765}}</ref><ref>{{Cite web|url=https://embryo.asu.edu/pages/nettie-maria-stevens-1861-1912|title=Nettie Maria Stevens (1861-1912) {{!}} The Embryo Project Encyclopedia|website=embryo.asu.edu|language=en|access-date=2018-06-07}}</ref>
==Chromosomal systems==

=== XX/XY sex chromosomes ===
[[File:Drosophila XY sex-determination.svg|thumb|Drosophila sex-chromosomes]]
[[File:Human male karyotpe high resolution - XY chromosome cropped.JPG|thumb|Human male XY chromosomes after [[G-banding]]]]
{{main|XY sex-determination system}}

The '''XX/XY sex-determination system''' is the most familiar, as it is found in humans. The XX/XY system is found in most other [[mammal]]s, as well as some insects. In this system, most females have two of the same kind of sex chromosome (XX), while most males have two distinct sex chromosomes (XY). The X and Y sex chromosomes are different in shape and size from each other, unlike the rest of the chromosomes ([[autosome]]s), and are sometimes called [[allosome]]s. In some species, such as humans, organisms remain sex indifferent for a time after they're created; in others, however, such as fruit flies, sexual differentiation occurs as soon as the egg is fertilized.<ref name=Hake/>

==== Y-centered sex determination ====

Some species (including humans) have a gene [[SRY]] on the Y chromosome that determines [[male]]ness. Members of SRY-reliant species can have uncommon XY chromosomal combinations such as [[Klinefelter syndrome|XXY]] and still live.<ref name=Hake>{{cite journal |last=Hake |first=Laura |title=Genetic Mechanisms of Sex Determination |journal=Nature Education |year=2008 |volume=1 |issue=1 |url=http://www.nature.com/scitable/topicpage/genetic-mechanisms-of-sex-determination-314 |accessdate=8 December 2011}}</ref>
Human sex is determined by the presence or absence of a Y chromosome with a functional SRY gene. Once the SRY gene is activated, cells create [[testosterone]] and [[anti-müllerian hormone]] which typically ensures the development of a single, male reproductive system.<ref name=Hake/> In typical XX embryos, cells secrete [[estrogen]], which drives the body toward the female pathway.

In Y-centered sex determination, the SRY gene is the main gene in determining male characteristics, but multiple genes are required to develop testes. In XY mice, lack of the gene [[DAX1]] on the X chromosome results in sterility, but in humans it causes [[adrenal hypoplasia congenita]].<ref name=Goodfellow>{{cite journal |author=Goodfellow, P. N. |title=DAX-1, an 'antitestis' gene |journal=Cellular and Molecular Life Sciences |year=1999 |pages=857–863 |volume=55 |issue=6–7 |doi=10.1007/PL00013201 |pmid=10412368 |last2=Camerino |first2=G.}}</ref> However, when an extra DAX1 gene is placed on the X chromosome, the result is a female, despite the existence of SRY.<ref name=Chandra>{{cite journal |author=Chandra, H. S. |title=Another way of looking at the enigma of sex determination in Ellobius lutescens |journal=Current Science |date=25 April 1999 |page=1072 |volume=76 |issue=8}}</ref> Even when there are normal sex chromosomes in XX females, duplication or expression of [[SOX9]] causes testes to develop.<ref name=Cox>{{cite journal |author=Cox, James J. |title=A SOX9 Duplication and Familial 46,XX Developmental Testicular Disorder |journal=New England Journal of Medicine |date=6 January 2011 |pages=91–93 |volume=364 |issue=1 |pmid=21208124 |last2=Willatt |first2=L |last3=Homfray |first3=T |last4=Woods |first4=C. G. |doi=10.1056/NEJMc1010311}}</ref><ref name=Huang>{{cite journal |author=Huang, Bing |title=Autosomal XX sex reversal caused by duplication of SOX9 |journal=American Journal of Medical Genetics |date=7 December 1999 |pages=349–353 |volume=87 |issue=4 |pmid=10588843 |last2=Wang |first2=S |last3=Ning |first3=Y |last4=Lamb |first4=A. N. |last5=Bartley |first5=J . |doi=10.1002/(SICI)1096-8628(19991203)87:4<349::AID-AJMG13>3.0.CO;2-N}}</ref> Gradual [[sex reversal]] in developed mice can also occur when the gene [[FOXL2]] is removed from females.<ref name=Uhlenhaut>{{cite journal |author=Uhlenhaut, Henriette N. |title=Somatic Sex Reprogramming of Adult Ovaries to Testes by FOXL2 Ablation |journal=Cell |date=11 December 2009 |pages=1130–1142 |volume=139 |issue=6 |doi= 10.1016/j.cell.2009.11.021 |pmid=20005806 |last2=Jakob |first2=S |last3=Anlag |first3=K |last4=Eisenberger |first4=T |last5=Sekido |first5=R |last6=Kress |first6=J |last7=Treier |first7=A. C. |last8=Klugmann |first8=C |last9=Klasen |first9=C |last10=Holter |first10=N. I. |last11=Riethmacher |first11=D |last12=Schütz |first12=G |last13=Cooney |first13=A. J. |last14=Lovell-Badge |first14=R |last15=Treier |first15=M|doi-access=free }}</ref> Even though the gene [[DMRT1]] is used by birds as their sex locus, species who have XY chromosomes also rely upon DMRT1, contained on chromosome 9, for sexual differentiation at some point in their formation.<ref name=Hake/>

==== X-centered sex determination ====

Some species, such as [[Drosophila melanogaster|fruit flies]], use the presence of two X chromosomes to determine [[female]]ness.<ref name=Penalva>{{cite journal |author=Penalva, Luiz O. F. |title=RNA Binding Protein Sex-Lethal (Sxl) and Control of Drosophila Sex Determination and Dosage Compensation |journal= Microbiology and Molecular Biology Reviews|date=September 2003 |pages=343–359 |volume=67 |issue=3 |doi=10.1128/MMBR.67.3.343-359.2003 |pmid=12966139 |pmc=193869 |last2=Sánchez }}</ref> Species that use the number of Xs to determine sex are nonviable with an extra X chromosome.

==== Other variants of XX/XY sex determination ====

Some fish have variants of the [[XY sex-determination system]], as well as the regular system. For example, while having an XY format, ''[[Xiphophorus nezahualcoyotl]]'' and ''X. milleri'' also have a second Y chromosome, known as Y', that creates XY' females and YY' males.<ref name=Schartl>{{cite journal | author = Schartl, Manfred | title = A comparative view on sex determination in medaka | journal = Mechanisms of Development | volume = 121 |issue=7–8 | pages = 639–645 | date = July 2004 | doi=10.1016/j.mod.2004.03.001 | pmid = 15210173}}</ref>

At least one [[monotreme]], the [[platypus#Evolution|platypus]], presents a particular sex determination scheme that in some ways resembles that of the [[ZW sex-determination system|ZW sex chromosomes]] of birds and lacks the SRY gene. The [[platypus]] has ten sex chromosomes; males have an XYXYXYXYXY pattern while females have ten X chromosomes. Although it is an XY system, the platypus' sex chromosomes share no homologues with [[eutherian]] sex chromosomes.<ref name=Warren>{{cite journal |title=Genome analysis of the platypus reveals unique signatures of evolution |journal=Nature |year=2008 |pages=175–U1 |volume=453 |doi=10.1038/nature06936 |issue=7192 |pmid=18464734 |pmc=2803040 |last2=Hillier |first2=Ladeana W. |last3=Marshall Graves |first3=Jennifer A. |last4=Birney |first4=Ewan | last5=Ponting |first5=Chris P. |last6=Grützner |first6=Frank |last7=Belov |first7=Katherine |last8=Miller |first8=Webb |last9=Clarke |first9=Laura |last10=Chinwalla |first10=Asif T. |last11=Yang |first11=Shiaw-Pyng |last12=Heger |first12=Andreas |last13=Locke |first13=Devin P. |last14=Miethke |first14=Pat |last15=Waters |first15=Paul D. |last16=Veyrunes |first16=Frédéric |last17=Fulton |first17=Lucinda |last18=Fulton |first18=Bob |last19=Graves |first19=Tina |last20=Wallis |first20=John |last21=Puente |first21=Xose S. |last22=López-Otín |first22=Carlos |last23=Ordóñez |first23=Gonzalo R. |last24=Eichler |first24=Evan E. |last25=Chen |first25=Lin |last26=Cheng |first26=Ze |last27=Deakin |first27=Janine E. |last28=Alsop |first28=Amber |last29=Thompson |first29=Katherine |last30=Kirby |first30=Patrick |display-authors=8 |last1 = Warren |first1 = W.C. |bibcode=2008Natur.453..175W}}</ref> Instead, homologues with eutherian sex chromosomes lie on the platypus chromosome 6, which means that the eutherian sex chromosomes were autosomes at the time that the monotremes diverged from the therian mammals (marsupials and eutherian mammals). However, homologues to the avian [[DMRT1]] gene on platypus sex chromosomes X3 and X5 suggest that it is possible the sex-determining gene for the platypus is the same one that is involved in bird sex-determination. More research must be conducted in order to determine the exact sex determining gene of the platypus.<ref name=Gruetzner>{{cite journal |author=Gruetzner, F. |author2=T. Ashley |author3=D. M. Rowell |author4=J. A. M. Graves |last-author-amp=yes |title=Analysis of the platypus reveals unique signatures of evolution |journal=Chromosoma |year=2006 |pages=75–88 |volume=115 |pmid=16344965 |issue=2 |doi=10.1007/s00412-005-0034-4}}</ref>

[[File:Critique of the Theory of Evolution Fig 060.jpg |thumb|Heredity of sex chromosomes in XO sex determination]]

=== XX/X0 sex chromosomes ===
{{Main |X0 sex-determination system}}

In this variant of the XY system, females have two copies of the sex chromosome (XX) but males have only one (X0). The ''0'' denotes the absence of a second sex chromosome. Generally in this method, the sex is determined by amount of genes expressed across the two chromosomes. This system is observed in a number of insects, including the grasshoppers and crickets of order [[Orthoptera]] and in cockroaches (order [[cockroach|Blattodea]]). A small number of mammals also lack a Y chromosome. These include the Amami spiny rat (''[[Tokudaia osimensis]]'') and the Tokunoshima spiny rat (''[[Tokudaia tokunoshimensis]]'') and ''Sorex araneus'', a [[shrew]] species. Transcaucasian mole voles (''[[Ellobius lutescens]]'') also have a form of XO determination, in which both sexes lack a second sex chromosome.<ref name=Chandra/> The mechanism of sex determination is not yet understood.<ref name=Kuroiwa>{{cite journal |vauthors=Kuroiwa A, Handa S, Nishiyama C, Chiba E, Yamada F, Abe S, Matsuda Y |title= Additional copies of CBX2 in the genomes of males of mammals lacking SRY, the Amami spiny rat (''Tokudaia osimensis'') and the Tokunoshima spiny rat (''Tokudaia tokunoshimensis'') |journal=Chromosome Res |date=8 June 2011 |pages=635–44 |volume=19 |issue= 5 |pmid=21656076 |doi=10.1007/s10577-011-9223-6}}</ref>

The [[nematode]] ''[[Caenorhabditis elegans|C. elegans]]'' is male with one sex chromosome (X0); with a pair of chromosomes (XX) it is a hermaphrodite.<ref name="Majerus">{{Harv |Majerus |2003 |page=60}}</ref> Its main sex gene is XOL, which encodes [[XOL-1 Switch protein N-terminal domain|XOL-1]] and also controls the expression of the genes TRA-2 and HER-1. These genes reduce male gene activation and increase it, respectively.<ref name=Kuwabara>{{cite journal |author=Patricia E. Kuwabara |author2=Peter G. Okkema |author3=Judith Kimble |title=tra-2 Encodes a Membrane Protein and May Mediate Cell Communication in the Caenorhabditis elegans Sex Determination Pathway |journal=Molecular Biology of the Cell |volume=3 |issue=4 |pages=461–73 |date=April 1992 |pmc=275596 |pmid=1498366 |doi=10.1091/mbc.3.4.461}}</ref>

=== ZW sex chromosomes ===
{{Main |ZW sex-determination system}}

The '''ZW sex-determination system''' is found in birds, some reptiles, and some insects and other organisms. The ZW sex-determination system is reversed compared to the XY system: females have two different kinds of [[chromosomes]] (ZW), and males have two of the same kind of chromosomes (ZZ). In the chicken, this was found to be dependent on the expression of DMRT1.<ref name="pmid19710650">{{cite journal | author1=Smith, C. A. | author2=Roeszler, K. N. | author3=Ohnesorg, T. | author4=Cummins, D. M. | author5=Farlie, P. G. | author6=Doran, T. J. | author7=Sinclair, A. H. | title=The avian Z-linked gene DMRT1 is required for male sex determination in the chicken | journal=Nature | volume=461 | issue=7261 | pages=267–271 | date=September 2009 | pmid=19710650 | doi=10.1038/nature08298 | bibcode=2009Natur.461..267S}}</ref> In birds, the genes FET1 and ASW are found on the W chromosome for females, similar to how the Y chromosome contains SRY.<ref name=Hake/> However, not all species depend upon the W for their sex. For example, there are moths and butterflies that are ZW, but some have been found female with ZO, as well as female with ZZW.<ref name="Majerus"/> Also, while mammals deactivate one of their extra X chromosomes when female, it appears that in the case of [[Lepidoptera]], the males produce double the normal amount of enzymes, due to having two Z's.<ref name="Majerus"/> Because the use of ZW sex determination is varied, it is still unknown how exactly most species determine their sex.<ref name="Majerus"/> However, reportedly, the silkworm ''Bombyx mori'' uses a single female-specific piRNA as the primary determiner of sex.<ref>{{cite journal |last1=Kiuchi |first1=Takashi |last2=Koga |first2=Hikaru |last3=Kawamoto |first3=Munetaka |last4=Shoji |first4=Keisuke |last5=Sakai |first5=Hiroki |last6=Arai |first6=Yuji |last7=Ishihara |first7=Genki |last8=Kawaoka |first8=Shinpei |last9=Sugano |first9=Sumio |last10=Shimada |first10=Toru |last11=Suzuki |first11=Yutaka |last12=Suzuki |first12=Masataka |last13=Katsuma |first13=Susumu |title=A single female-specific piRNA is the primary determiner of sex in the silkworm |journal=Nature |date=14 May 2014 |volume=509 |pages=633–636 |doi=10.1038/nature13315 |pmid=24828047 |issue=7502 |bibcode=2014Natur.509..633K}}</ref> Despite the similarities between the ZW and XY systems, these sex chromosomes evolved separately. In the case of the chicken, their Z chromosome is more similar to humans' autosome 9.<ref name=Stiglec>{{cite journal |author1=Stiglec, R. |author2=Ezaz, T. |author3=Graves, J. A. |title=A new look at the evolution of avian sex chromosomes |journal=Cytogenet. Genome Res. |volume=117 |issue=1–4 |pages=103–9 |year=2007 |pmid=17675850 |doi=10.1159/000103170}}</ref> The chicken's Z chromosome also seems to be related to the X chromosome of the platypus.<ref name=Grutzner>{{cite journal | last=Grützner | first=F. | author2=Rens, W. | author3=Tsend-Ayush, E. | author4=El-Mogharbel, N. | author5=O'Brien, P. C. M. | author6=Jones, R. C. | author7=Ferguson-Smith, M. A. | author8=Marshall, J. A. | last-author-amp=yes | year=2004 | title=In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes | journal=[[Nature (journal)|Nature]] | volume=432 | pages=913–917 | doi=10.1038/nature03021 | pmid=15502814 | issue=7019 | bibcode=2004Natur.432..913G }}</ref> When a ZW species, such as the [[Komodo dragon]], reproduces parthenogenetically, usually only males are produced. This is due to the fact that the haploid eggs double their chromosomes, resulting in ZZ or WW. The ZZ become males, but the WW are not viable and are not brought to term.<ref name="BBC">{{cite news |work=BBC News |url=http://news.bbc.co.uk/2/hi/science/nature/6196225.stm |title=Virgin births for giant lizards |accessdate=13 March 2008 | date=20 December 2006}}</ref>

===UV sex chromosomes===
In some [[Bryophyte]] and some [[algae]] species, the [[gametophyte]] stage of the life cycle, rather than being hermaphrodite, occurs as separate male or female individuals that produce male and female gametes respectively. When meiosis occurs in the [[sporophyte]] generation of the life cycle, the sex chromosomes known as U and V assort in spores that carry either the U chromosome and give rise to female gametophytes, or the V chromosome and give rise to male gametophytes.<ref name="pmid21962970">{{cite journal | vauthors = Bachtrog D, Kirkpatrick M, Mank JE, McDaniel SF, Pires JC, Rice W, Valenzuela N | title = Are all sex chromosomes created equal? | journal = Trends Genet. | volume = 27 | issue = 9 | pages = 350–7 | date = September 2011 | pmid = 21962970 | doi = 10.1016/j.tig.2011.05.005 }}</ref><ref>{{cite journal |author1=Renner, S. S. |author2=Heinrichs, J. |author3=Sousa, A. |year=2017 |title= The sex chromosomes of bryophytes: Recent insights, open questions, and reinvestigations of Frullania dilatata and Plagiochila asplenioides. |journal=Journal of Systematics and Evolution |volume=55 |issue=4 |pages=333–339 |doi=10.1111/jse.12266|doi-access=free }}</ref>

[[File:Haplodiploid-sex-determination-system3.png |thumb|Haplodiploid sex chromosomes]]

=== Haplodiploidy ===
{{main|Haplodiploidy}}

[[Haplodiploidy]] is found in insects belonging to [[Hymenoptera]], such as [[ant]]s and [[bee]]s. Unfertilized eggs develop into [[haploid]] individuals, which are the males. [[Diploid]] individuals are generally female but may be sterile males. Males cannot have sons or fathers. If a queen bee mates with one drone, her daughters share ¾ of their genes with each other, not ½ as in the XY and ZW systems. This may be significant for the development of [[eusociality]], as it increases the significance of [[kin selection]], but it is debated.<ref name=eowilson>{{cite journal | author = Edward O. Wilson | authorlink = Edward O. Wilson | title = Kin selection as the key to altruism: its rise and fall. | journal = Social Research | volume = 72 | pages = 1–8 | date = 12 September 2005 | url = http://www.thefreelibrary.com/Kin+selection+as+the+key+to+altruism%3A+its+rise+and+fall.-a0132354420 | format = PDF | accessdate =25 March 2011}}</ref> Most females in the Hymenoptera order can decide the sex of their offspring by holding received sperm in their [[spermatheca]] and either releasing it into their oviduct or not. This allows them to create more workers, depending on the status of the colony.<ref name=Wilgenburg>{{cite journal | author = Ellen van Wilgenburg | title = Single locus complementary sex determination in Hymenoptera: an "unintelligent" design? | journal = Frontiers in Zoology | volume = 3 | issue=1 | pages = 1 | date = 5 January 2006 |doi=10.1186/1742-9994-3-1 | pmid = 16393347 | pmc = 1360072 | last2 = Driessen | first2 = Gerard | last3 = Beukeboom | first3 = Leow}}</ref>

১০:১০, ১৯ মে ২০২০ তারিখে সংশোধিত সংস্করণ

প্রাণীতে কিছু ক্রোমোজোম লিঙ্গ নির্ধারণ পদ্ধতি

লিঙ্গ নির্ধারণ ব্যবস্থা একটি জৈবিক পদ্ধতি যা একটি জীব এর মধ্যে যৌন বৈশিষ্ট্যের বিকাশ নির্ধারণ করে। বেশিরভাগ জীব যারা যৌন প্রজনন ব্যবহার করে বংশবৃদ্ধি করে তাদের দুটি লিঙ্গ থাকে। মাঝে মধ্যে একটি বা উভয় লিঙ্গের জায়গায় হার্মাফ্রোডাইট থাকে। এছাড়াও কিছু প্রজাতি রয়েছে যা পার্থেনোজেনেসিস এর কারণে কেবল একটি লিঙ্গ, নিষেককরণ ছাড়াই স্ত্রী প্রজনন করার কাজ করে।

অনেক প্রজাতিতে লিঙ্গ নির্ধারণ জিনগত: পুরুষ ও স্ত্রীদের অ্যালিল গুলি বা এমনকি আলাদা জিন গুলি থাকে যা তাদের যৌন মরফোলজি নির্দিষ্ট করে। সাধারণত এক্সওয়াই, জেডডাব্লু, এক্সও, জেডও ক্রোমোজোম বা হ্যাপলডিপ্লয়েডির সংমিশ্রণের মাধ্যমে প্রাণীদের মধ্যে প্রায়শই ক্রোমোসোমাল পার্থক্য তৈরি হয়। যৌন ভিন্নতা সাধারণত একটি প্রধান জিন ("সেক্স লোকস") দ্বারা চালিত হয়, এবং অন্যান্য জিনগুলি একটি ডোমিনো প্রভাব অনুসরণ করে।

অন্যান্য ক্ষেত্রে, একটি ভ্রূণের লিঙ্গ নির্ধারণ করা হয় পরিবেশগত ভেরিয়েবলগুলি (যেমন তাপমাত্রা)) দ্বারা। কিছু যৌন-নির্ধারণ ব্যবস্থার বিবরণ এখনও পুরোপুরি বোঝা যায় নি। ভবিষ্যতের ভ্রূণের জৈবিক সিস্টেম বিশ্লেষণের আশাগুলির মধ্যে সম্পূর্ণ প্রজনন-সিস্টেম সূচনা সংকেত অন্তর্ভুক্ত যা গর্ভধারণের সময় ভ্রূণের একটি নির্ধারিত লিঙ্গ পুরুষ, বা মহিলা কিনা তা আরও নিখুঁতভাবে নির্ধারণের জন্য পরিমাপ করা যেতে পারে। জৈবিক ব্যবস্থার এই জাতীয় বিশ্লেষণটি ভ্রূণ হার্মফ্রোডাইট কিনা তাও ইঙ্গিত দিতে পারে, যার মধ্যে পুরুষ এবং মহিলা উভয় প্রজনন অঙ্গের মোট বা আংশিক অন্তর্ভুক্ত রয়েছে।

কিছু প্রজাতি যেমন বিভিন্ন উদ্ভিদ এবং মাছের একটি নির্দিষ্ট লিঙ্গ থাকে না এবং পরিবর্তে জীবনচক্র হয় এবং সম্পর্কিত জীবনের পর্যায়ে তারা জিনগত সূত্রের ভিত্তিতে লিঙ্গ পরিবর্তন করে। এটি মৌসুম এবং তাপমাত্রার মতো পরিবেশগত কারণগুলির কারণে হতে পারে। ভ্রূণের যৌন-নির্ধারণীকরণ ব্যবস্থায় পরিবর্তনের কারণে মানব ভ্রূণের যৌনাঙ্গে কখনও কখনও অস্বাভাবিকতা দেখা দিতে পারে ফলস্বরূপ ভ্রূণ আন্তঃআকৃতির হয়ে যায়।

আবিষ্কার

১৯০৩ সালে আমেরিকান জিনতত্ত্ববিদ নেটটি স্টিভেনস দ্বারা খাবারের কীট এর লিঙ্গ নির্ধারণ ব্যবস্থা আবিষ্কার হয়েছিলো।[১][২][৩]

Chromosomal systems

XX/XY sex chromosomes

Drosophila sex-chromosomes
Human male XY chromosomes after G-banding
মূল নিবন্ধ: XY sex-determination system

The XX/XY sex-determination system is the most familiar, as it is found in humans. The XX/XY system is found in most other mammals, as well as some insects. In this system, most females have two of the same kind of sex chromosome (XX), while most males have two distinct sex chromosomes (XY). The X and Y sex chromosomes are different in shape and size from each other, unlike the rest of the chromosomes (autosomes), and are sometimes called allosomes. In some species, such as humans, organisms remain sex indifferent for a time after they're created; in others, however, such as fruit flies, sexual differentiation occurs as soon as the egg is fertilized.[৪]

Y-centered sex determination

Some species (including humans) have a gene SRY on the Y chromosome that determines maleness. Members of SRY-reliant species can have uncommon XY chromosomal combinations such as XXY and still live.[৪] Human sex is determined by the presence or absence of a Y chromosome with a functional SRY gene. Once the SRY gene is activated, cells create testosterone and anti-müllerian hormone which typically ensures the development of a single, male reproductive system.[৪] In typical XX embryos, cells secrete estrogen, which drives the body toward the female pathway.

In Y-centered sex determination, the SRY gene is the main gene in determining male characteristics, but multiple genes are required to develop testes. In XY mice, lack of the gene DAX1 on the X chromosome results in sterility, but in humans it causes adrenal hypoplasia congenita.[৫] However, when an extra DAX1 gene is placed on the X chromosome, the result is a female, despite the existence of SRY.[৬] Even when there are normal sex chromosomes in XX females, duplication or expression of SOX9 causes testes to develop.[৭][৮] Gradual sex reversal in developed mice can also occur when the gene FOXL2 is removed from females.[৯] Even though the gene DMRT1 is used by birds as their sex locus, species who have XY chromosomes also rely upon DMRT1, contained on chromosome 9, for sexual differentiation at some point in their formation.[৪]

X-centered sex determination

Some species, such as fruit flies, use the presence of two X chromosomes to determine femaleness.[১০] Species that use the number of Xs to determine sex are nonviable with an extra X chromosome.

Other variants of XX/XY sex determination

Some fish have variants of the XY sex-determination system, as well as the regular system. For example, while having an XY format, Xiphophorus nezahualcoyotl and X. milleri also have a second Y chromosome, known as Y', that creates XY' females and YY' males.[১১]

At least one monotreme, the platypus, presents a particular sex determination scheme that in some ways resembles that of the ZW sex chromosomes of birds and lacks the SRY gene. The platypus has ten sex chromosomes; males have an XYXYXYXYXY pattern while females have ten X chromosomes. Although it is an XY system, the platypus' sex chromosomes share no homologues with eutherian sex chromosomes.[১২] Instead, homologues with eutherian sex chromosomes lie on the platypus chromosome 6, which means that the eutherian sex chromosomes were autosomes at the time that the monotremes diverged from the therian mammals (marsupials and eutherian mammals). However, homologues to the avian DMRT1 gene on platypus sex chromosomes X3 and X5 suggest that it is possible the sex-determining gene for the platypus is the same one that is involved in bird sex-determination. More research must be conducted in order to determine the exact sex determining gene of the platypus.[১৩]

Heredity of sex chromosomes in XO sex determination

XX/X0 sex chromosomes

মূল নিবন্ধ: X0 sex-determination system

In this variant of the XY system, females have two copies of the sex chromosome (XX) but males have only one (X0). The 0 denotes the absence of a second sex chromosome. Generally in this method, the sex is determined by amount of genes expressed across the two chromosomes. This system is observed in a number of insects, including the grasshoppers and crickets of order Orthoptera and in cockroaches (order Blattodea). A small number of mammals also lack a Y chromosome. These include the Amami spiny rat (Tokudaia osimensis) and the Tokunoshima spiny rat (Tokudaia tokunoshimensis) and Sorex araneus, a shrew species. Transcaucasian mole voles (Ellobius lutescens) also have a form of XO determination, in which both sexes lack a second sex chromosome.[৬] The mechanism of sex determination is not yet understood.[১৪]

The nematode C. elegans is male with one sex chromosome (X0); with a pair of chromosomes (XX) it is a hermaphrodite.[১৫] Its main sex gene is XOL, which encodes XOL-1 and also controls the expression of the genes TRA-2 and HER-1. These genes reduce male gene activation and increase it, respectively.[১৬]

ZW sex chromosomes

মূল নিবন্ধ: ZW sex-determination system

The ZW sex-determination system is found in birds, some reptiles, and some insects and other organisms. The ZW sex-determination system is reversed compared to the XY system: females have two different kinds of chromosomes (ZW), and males have two of the same kind of chromosomes (ZZ). In the chicken, this was found to be dependent on the expression of DMRT1.[১৭] In birds, the genes FET1 and ASW are found on the W chromosome for females, similar to how the Y chromosome contains SRY.[৪] However, not all species depend upon the W for their sex. For example, there are moths and butterflies that are ZW, but some have been found female with ZO, as well as female with ZZW.[১৫] Also, while mammals deactivate one of their extra X chromosomes when female, it appears that in the case of Lepidoptera, the males produce double the normal amount of enzymes, due to having two Z's.[১৫] Because the use of ZW sex determination is varied, it is still unknown how exactly most species determine their sex.[১৫] However, reportedly, the silkworm Bombyx mori uses a single female-specific piRNA as the primary determiner of sex.[১৮] Despite the similarities between the ZW and XY systems, these sex chromosomes evolved separately. In the case of the chicken, their Z chromosome is more similar to humans' autosome 9.[১৯] The chicken's Z chromosome also seems to be related to the X chromosome of the platypus.[২০] When a ZW species, such as the Komodo dragon, reproduces parthenogenetically, usually only males are produced. This is due to the fact that the haploid eggs double their chromosomes, resulting in ZZ or WW. The ZZ become males, but the WW are not viable and are not brought to term.[২১]

UV sex chromosomes

In some Bryophyte and some algae species, the gametophyte stage of the life cycle, rather than being hermaphrodite, occurs as separate male or female individuals that produce male and female gametes respectively. When meiosis occurs in the sporophyte generation of the life cycle, the sex chromosomes known as U and V assort in spores that carry either the U chromosome and give rise to female gametophytes, or the V chromosome and give rise to male gametophytes.[২২][২৩]

Haplodiploid sex chromosomes

Haplodiploidy

মূল নিবন্ধ: Haplodiploidy

Haplodiploidy is found in insects belonging to Hymenoptera, such as ants and bees. Unfertilized eggs develop into haploid individuals, which are the males. Diploid individuals are generally female but may be sterile males. Males cannot have sons or fathers. If a queen bee mates with one drone, her daughters share ¾ of their genes with each other, not ½ as in the XY and ZW systems. This may be significant for the development of eusociality, as it increases the significance of kin selection, but it is debated.[২৪] Most females in the Hymenoptera order can decide the sex of their offspring by holding received sperm in their spermatheca and either releasing it into their oviduct or not. This allows them to create more workers, depending on the status of the colony.[২৫]

  1. ↑ "Nettie Stevens: A Discoverer of Sex Chromosomes | Learn Science at Scitable"। www.nature.com (ইংরেজি ভাষায়)। সংগ্রহের তারিখ ২০১৮-০৬-০৭। 
  2. ↑ Ogilvie, Marilyn Bailey; Choquette, Clifford J. (১৯৮১)। "Nettie Maria Stevens (1861-1912): Her Life and Contributions to Cytogenetics"। Proceedings of the American Philosophical Society। 125 (4): 292–311। জেস্টোর 986332। পিএমআইডি 11620765। 
  3. ↑ "Nettie Maria Stevens (1861-1912) | The Embryo Project Encyclopedia"। embryo.asu.edu (ইংরেজি ভাষায়)। সংগ্রহের তারিখ ২০১৮-০৬-০৭। 
  4. ↑ ক খ গ ঘ ঙ Hake, Laura (২০০৮)। "Genetic Mechanisms of Sex Determination"। Nature Education। 1 (1)। সংগ্রহের তারিখ ৮ ডিসেম্বর ২০১১। 
  5. ↑ Goodfellow, P. N.; Camerino, G. (১৯৯৯)। "DAX-1, an 'antitestis' gene"। Cellular and Molecular Life Sciences। 55 (6–7): 857–863। ডিওআই:10.1007/PL00013201। পিএমআইডি 10412368। 
  6. ↑ ক খ Chandra, H. S. (২৫ এপ্রিল ১৯৯৯)। "Another way of looking at the enigma of sex determination in Ellobius lutescens"। Current Science। 76 (8): 1072। 
  7. ↑ Cox, James J.; Willatt, L; Homfray, T; Woods, C. G. (৬ জানুয়ারি ২০১১)। "A SOX9 Duplication and Familial 46,XX Developmental Testicular Disorder"। New England Journal of Medicine। 364 (1): 91–93। ডিওআই:10.1056/NEJMc1010311। পিএমআইডি 21208124। 
  8. ↑ Huang, Bing; Wang, S; Ning, Y; Lamb, A. N.; Bartley, J . (৭ ডিসেম্বর ১৯৯৯)। "Autosomal XX sex reversal caused by duplication of SOX9"। American Journal of Medical Genetics। 87 (4): 349–353। ডিওআই:10.1002/(SICI)1096-8628(19991203)87:4<349::AID-AJMG13>3.0.CO;2-N। পিএমআইডি 10588843। 
  9. ↑ Uhlenhaut, Henriette N.; Jakob, S; Anlag, K; Eisenberger, T; Sekido, R; Kress, J; Treier, A. C.; Klugmann, C; Klasen, C; Holter, N. I.; Riethmacher, D; Schütz, G; Cooney, A. J.; Lovell-Badge, R; Treier, M (১১ ডিসেম্বর ২০০৯)। "Somatic Sex Reprogramming of Adult Ovaries to Testes by FOXL2 Ablation"। Cell। 139 (6): 1130–1142। ডিওআই:10.1016/j.cell.2009.11.021 অবাধে প্রবেশযোগ্য। পিএমআইডি 20005806। 
  10. ↑ Penalva, Luiz O. F.; Sánchez (সেপ্টেম্বর ২০০৩)। "RNA Binding Protein Sex-Lethal (Sxl) and Control of Drosophila Sex Determination and Dosage Compensation"। Microbiology and Molecular Biology Reviews। 67 (3): 343–359। ডিওআই:10.1128/MMBR.67.3.343-359.2003। পিএমআইডি 12966139। পিএমসি 193869 অবাধে প্রবেশযোগ্য। 
  11. ↑ Schartl, Manfred (জুলাই ২০০৪)। "A comparative view on sex determination in medaka"। Mechanisms of Development। 121 (7–8): 639–645। ডিওআই:10.1016/j.mod.2004.03.001। পিএমআইডি 15210173। 
  12. ↑ Warren, W.C.; Hillier, Ladeana W.; Marshall Graves, Jennifer A.; Birney, Ewan; Ponting, Chris P.; Grützner, Frank; Belov, Katherine; Miller, Webb; ও অন্যান্য (২০০৮)। "Genome analysis of the platypus reveals unique signatures of evolution"। Nature। 453 (7192): 175–U1। ডিওআই:10.1038/nature06936। পিএমআইডি 18464734। পিএমসি 2803040 অবাধে প্রবেশযোগ্য। বিবকোড:2008Natur.453..175W। 
  13. ↑ Gruetzner, F.; T. Ashley; D. M. Rowell & J. A. M. Graves (২০০৬)। "Analysis of the platypus reveals unique signatures of evolution"। Chromosoma। 115 (2): 75–88। ডিওআই:10.1007/s00412-005-0034-4। পিএমআইডি 16344965। 
  14. ↑ Kuroiwa A, Handa S, Nishiyama C, Chiba E, Yamada F, Abe S, Matsuda Y (৮ জুন ২০১১)। "Additional copies of CBX2 in the genomes of males of mammals lacking SRY, the Amami spiny rat (Tokudaia osimensis) and the Tokunoshima spiny rat (Tokudaia tokunoshimensis)"। Chromosome Res। 19 (5): 635–44। ডিওআই:10.1007/s10577-011-9223-6। পিএমআইডি 21656076। 
  15. ↑ ক খ গ ঘ (Majerus 2003, পৃ. 60)
  16. ↑ Patricia E. Kuwabara; Peter G. Okkema; Judith Kimble (এপ্রিল ১৯৯২)। "tra-2 Encodes a Membrane Protein and May Mediate Cell Communication in the Caenorhabditis elegans Sex Determination Pathway"। Molecular Biology of the Cell। 3 (4): 461–73। ডিওআই:10.1091/mbc.3.4.461। পিএমআইডি 1498366। পিএমসি 275596 অবাধে প্রবেশযোগ্য। 
  17. ↑ Smith, C. A.; Roeszler, K. N.; Ohnesorg, T.; Cummins, D. M.; Farlie, P. G.; Doran, T. J.; Sinclair, A. H. (সেপ্টেম্বর ২০০৯)। "The avian Z-linked gene DMRT1 is required for male sex determination in the chicken"। Nature। 461 (7261): 267–271। ডিওআই:10.1038/nature08298। পিএমআইডি 19710650। বিবকোড:2009Natur.461..267S। 
  18. ↑ Kiuchi, Takashi; Koga, Hikaru; Kawamoto, Munetaka; Shoji, Keisuke; Sakai, Hiroki; Arai, Yuji; Ishihara, Genki; Kawaoka, Shinpei; Sugano, Sumio; Shimada, Toru; Suzuki, Yutaka; Suzuki, Masataka; Katsuma, Susumu (১৪ মে ২০১৪)। "A single female-specific piRNA is the primary determiner of sex in the silkworm"। Nature। 509 (7502): 633–636। ডিওআই:10.1038/nature13315। পিএমআইডি 24828047। বিবকোড:2014Natur.509..633K। 
  19. ↑ Stiglec, R.; Ezaz, T.; Graves, J. A. (২০০৭)। "A new look at the evolution of avian sex chromosomes"। Cytogenet. Genome Res.। 117 (1–4): 103–9। ডিওআই:10.1159/000103170। পিএমআইডি 17675850। 
  20. ↑ Grützner, F.; Rens, W.; Tsend-Ayush, E.; El-Mogharbel, N.; O'Brien, P. C. M.; Jones, R. C.; Ferguson-Smith, M. A. & Marshall, J. A. (২০০৪)। "In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes"। Nature। 432 (7019): 913–917। ডিওআই:10.1038/nature03021। পিএমআইডি 15502814। বিবকোড:2004Natur.432..913G। 
  21. ↑ "Virgin births for giant lizards"। BBC News। ২০ ডিসেম্বর ২০০৬। সংগ্রহের তারিখ ১৩ মার্চ ২০০৮। 
  22. ↑ Bachtrog D, Kirkpatrick M, Mank JE, McDaniel SF, Pires JC, Rice W, Valenzuela N (সেপ্টেম্বর ২০১১)। "Are all sex chromosomes created equal?"। Trends Genet.। 27 (9): 350–7। ডিওআই:10.1016/j.tig.2011.05.005। পিএমআইডি 21962970। 
  23. ↑ Renner, S. S.; Heinrichs, J.; Sousa, A. (২০১৭)। "The sex chromosomes of bryophytes: Recent insights, open questions, and reinvestigations of Frullania dilatata and Plagiochila asplenioides."। Journal of Systematics and Evolution। 55 (4): 333–339। ডিওআই:10.1111/jse.12266 অবাধে প্রবেশযোগ্য। 
  24. ↑ Edward O. Wilson (১২ সেপ্টেম্বর ২০০৫)। "Kin selection as the key to altruism: its rise and fall." (PDF)। Social Research। 72: 1–8। সংগ্রহের তারিখ ২৫ মার্চ ২০১১। 
  25. ↑ Ellen van Wilgenburg; Driessen, Gerard; Beukeboom, Leow (৫ জানুয়ারি ২০০৬)। "Single locus complementary sex determination in Hymenoptera: an "unintelligent" design?"। Frontiers in Zoology। 3 (1): 1। ডিওআই:10.1186/1742-9994-3-1। পিএমআইডি 16393347। পিএমসি 1360072 অবাধে প্রবেশযোগ্য। 
'https://bn.wikipedia.org/w/index.php?title=লিঙ্গ_নির্ধারণ_ব্যবস্থা&oldid=4252785' থেকে আনীত