Genetics
Genetics shine nazarin kwayoyin halitta, bambancin kwayoyin halitta, da kuma gado a cikin kwayoyin halitta.    Wani reshe ne mai mahimmanci a ilmin halitta saboda gado yana da mahimmanci ga juyin halitta. 

Gregor Mendel, dan kabilar Moravian Augustinian mai aiki a karni na 19 a Brno, shi ne na farko da ya fara nazarin kwayoyin halitta a kimiyance. Mendel ya yi nazarin "gadon dabi'a", alamu a cikin yadda ake ba da halaye daga iyaye zuwa zuriya na tsawon lokaci. Ya lura cewa kwayoyin halitta (tsiran fis) suna gadar halaye ta hanyar “raka’a na gado” masu hankali. Wannan kalma, da har yanzu ake amfani da ita a yau, ita ce ma'aamara rikitarwa r da akkira a da s n kwayar halitta.

Halin gado da tsarin gado na kwayoyin halitta da kwayoyin halitta har yanzu sune ka'idojin farko na kwayoyin halitta a karni na 21, amma kwayoyin halitta na zamani sun fadada don nazarin aiki da halayen kwayoyin halitta. Tsarin Halittu da aiki, bambance-bambance, da rarraba ana nazarin su a cikin mahallin kwayar halitta, kwayoyin halitta (misali rinjaye ), da kuma cikin mahallin yawan jama'a. Genetics ya haifar da wasu ƙananan filayen, ciki har da kwayoyin halitta kwayoyin halitta, epigenetics da yawan kwayoyin halitta . Kwayoyin da aka yi nazari a cikin faffadan fage sun mamaye sassan rayuwa ( archaea, bakteriya, da eukarya ).

Tsarin kwayoyin halitta suna aiki tare da yanayin kwayoyin halitta da gogewa don yin tasiri ga haɓakawa da ɗabi'a, galibi ana magana da ita azaman yanayi tare da haɓakawa. Wurin hantsi ko waje na tantanin halitta mai rai ko kwayoyin halitta na iya canza rubutun kwayoyin halitta a kunne ko kashe. Misali na yau da kullun shine nau'in masara iri ɗaya iri biyu, wanda aka sanya shi a cikin yanayi mai zafi ɗaya kuma cikin yanayi mara kyau (rashin isassun ruwa ko ruwan sama). Yayin da za a iya tantance matsakaicin tsayin dawakai guda biyu na masara don zama daidai, wanda ke cikin yanayi mai bushewa kawai yakan girma zuwa rabin tsayin da yake a cikin yanayin yanayi saboda rashin ruwa da abinci mai gina jiki a muhallinsa.

Muna buƙatar ƙarin sani game da ilimin halitta na ƙwayoyin cuta saboda nazarin kwayoyin halitta. Kwayar halittar kwayar cutar, wacce ta kunshi sassan RNA masu madauri biyu 11, tana aiki a matsayin ma’anarta. Siffa ta farko na kwayoyin halittar hoto ko bidiyo mai zagaya yanar gizo da sauri ita ce ikon tsarin halittar kwayoyin halitta don sake sanya sassan kwayoyin halitta yayin kamuwa da cuta mai gauraye. 

Bayan sake gano aikin Mendel, masana kimiyya sun yi ƙoƙari su tantance waɗanne kwayoyin halitta a cikin tantanin halitta ke da alhakin gado. A cikin 1900, Nettie Stevens ya fara nazarin cin abinci.  A cikin shekaru 11 masu zuwa, ta gano cewa mata kawai suna da X chromosome kuma maza suna da duka X da Y chromosomes.  Ta iya yanke shawarar cewa jima'i wani abu ne na chromosomal kuma namiji ne ya ƙaddara.  A cikin 1911, Thomas Hunt Morgan yayi jayayya cewa kwayoyin halitta suna kan chromosomes, bisa la'akari da maye gurbin farin ido mai dangantaka da jima'i a cikin kwari 'ya'yan itace . A cikin 1913, ɗalibinsa Alfred Sturtevant ya yi amfani da yanayin haɗin gwiwar kwayoyin halitta don nuna cewa an tsara kwayoyin halitta a kan chromosome.

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