234 ghÐp bé bèn Di truyÒn cña c¸c alen trong thÓ tø béi tù d-ìng. Mét kiÓu gen AAAa sÏ s¶n xuÊt c¸c giao tö AA, Aa víi tû lÖ 3:1. qualitative trait A trait that shows Qq discontinuous variation - i.e. individuals can be assigned to one of a small number of discrete classes. tÝnh tr¹ng chÊt l-îng Mét tÝnh tr¹ng cho q Denotes the longer of the two thÊy biÕn dÞ kh«ng liªn tôc- nghÜa lμ c¸c c¸ chromosome arms, e.g. human 10q is the thÓ cã thÓ ®-îc g¸n cho mét sè l-îng nhá long arm of human chromosome 10. c¸c líp t¸ch biÖt. q BiÓu thÞ nh¸nh dμi cña hai nh¸nh nhiÔm quantitative genetics The area of s¾c thÓ, vÝ dô ng-êi 10q lμ nh¸nh dμi cña genetics concerned with the inheritance nhiÔm s¾c thÓ sè 10 cña ng-êi. of quantitative traits that show continuous q-beta replicase A viral RNA polymerase variation, as opposed to qualitative traits. secreted by a bacteriophage that infects Since many of the critical targets in both E. coli. It has the property of being able to plant and animal breeding are of this type, copy RNA sequences at a rapid rate. most practical improvement programs involve the application of quantitative q-beta replicaza RNA polymerase virut genetics. ®-îc ph©n tiÕt do thÓ thùc khuÈn l©y nhiÔm E. coli. Cã thuéc tÝnh diÔn ra kh¶ n¨ng sao di truyÒn häc sè l-îng LÜnh vùc di truyÒn chÐp tr×nh tù RNA víi nhÞp ®é nhanh. häc liªn quan víi di truyÒn tÝnh tr¹ng sè l-îng cho thÊy biÕn dÞ liªn tôc, ng-îc víi QSAR viÕt t¾t cña quantitative structure- tÝnh tr¹ng chÊt l-îng. V× nhiÒu môc ®Ých activity relationship phª ph¸n trong nh©n gièng sinh s¶n c¶ QTL viÕt t¾t cña quantitative trait locus. thùc vËt vμ ®éng vËt nu«i ®Òu thuéc lo¹i quadrivalent A chromosome configuration nμy, hÇu hÕt c¸c ch-¬ng tr×nh n©ng cao visible in late prophase and metaphase thùc hμnh bao gåm øng dông di truyÒn häc of the first meiotic division, where four sè l-îng. chromosomes are linked by chiasmata. quantitative inheritance Inheritance of Can occur in autotetraploids when four measurable traits that depend on the homologous chromosomes pair, or in cumulative action of many genes and/or diploids as a result of heterozygosity for involve a significant proportion of non- a reciprocal translocation between two genetic determination. non-homologous chromosomes. di truyÒn sè l-îng Di truyÒn nh÷ng tÝnh ®ång hãa trÞ CÊu h×nh nhiÔm s¾c thÓ nh×n tr¹ng ®o ®-îc mμ phô thuéc vμo ho¹t ®éng thÊy râ trong cuèi k× ®Çu vμ k× gi÷a ph©n tÝch tô cña nhiÒu gen vμ/hoÆc bao gåm mét chia gi¶m ph©n lÇn ®Çu, n¬i bèn nhiÔm s¾c tØ lÖ quan träng yÕu tè x¸c ®Þnh kh«ng di thÓ liªn kÕt do b¾t chÐo. Cã thÓ xuÊt hiÖn truyÒn. trong thÓ tø béi tù d-ìng khi bèn nhiÔm quantitative structure-activity s¾c thÓ t-¬ng ®ång cÆp ®«i, hoÆc trong relationship (Abbreviation QSAR). A l-ìng béi lμ hËu qu¶ cña tÝnh dÞ hîp tö v× computer modelling technique that ho¸n vÞ thuËn nghÞch gi÷a hai nhiÔm s¾c enables the prediction of the likely activity thÓ kh«ng t-¬ng ®ång. of a molecule before it is synthesized. quadruplex The inheritance of alleles in QSAR analysis relies on recognizing autotetraploids. A genotype AAAa will associations of molecular structures and produce gametes AA, Aa in the ratio 3:1. activity from historical data. quantitative trait 235 quan hÖ ho¹t ®éng - cÊu tróc sè l-îng quarantine Isolation for a period after (viÕt t¾t QSAR). Mét kü thuËt m« h×nh tÝnh arrival in a new location, to allow any pre- to¸n cho phÐp dù ®o¸n ho¹t ®éng cña mét existing disease symptoms to appear. ph©n tö gièng hÖt tr-íc khi nã ®-îc tæng Used in the context of regulations hîp. Sù ph©n tÝch QSAR tin cËy vμo nh÷ng restricting the sale or shipment of living mèi quan hÖ nhËn biÕt vÒ cÊu tróc ph©n tö organisms, usually to prevent disease or vμ ho¹t ®éng tõ d÷ liÖu tiÒn sö. pest invasion of an area. quantitative trait A measurable trait that c¸ch ly kiÓm dÞch C« lËp mét thêi kú sau shows continuous variation (e.g. height, khi ®Õn vÞ trÝ míi, cho phÐp bÊt kú nh÷ng weight, colour intensity, etc.) - i.e. the triÖu chøng bÖnh vèn cã tõ tr-íc xuÊt hiÖn. population cannot be classified into a few Dïng trong khung ®iÒu chØnh h¹n chÕ hμng discrete classes. b¸n hoÆc xuÊt khÈu c¸c sinh vËt sèng, tÝnh tr¹ng sè l-îng Mét tÝnh tr¹ng ®o ®-îc th-êng ®Ó ng¨n ngõa t¸c nh©n s©u hoÆc cho thÊy biÕn dÞ liªn tôc (vÝ dô chiÒu cao, bÖnh h¹i cña mét vïng. träng l-îng, ®é mμu, v.v.) - nghÜa lμ mét quaternary structure A level of protein quÇn thÓ kh«ng thÓ ph©n lo¹i thμnh mét structure where several individual sè Ýt líp riªng biÖt. molecules assemble together and form a quantitative trait locus (Abbreviation: functional cluster. A classic example is QTL). A locus where allelic variation is haemoglobin, a complex of four myoglobin- associated with variation in a quantitative like units. See: tertiary structure. trait. The presence of a QTL is inferred cÊu tróc bËc bèn Møc cÊu tróc protein from genetic mapping, where the total n¬i mét sè Ýt ph©n tö riªng lÎ tËp hîp l¹i vμ variation is partitioned into components h×nh thμnh mét khèi ho¹t ®éng. Mét vÝ dô linked to a number of discrete kinh ®iÓn lμ haemoglobin, mét phøc hÖ bèn chromosome regions. ®¬n vÞ gièng nh- myoglobin. Xem: tertiary æ gen tÝnh tr¹ng sè l-îng (viÕt t¾t: QTL). structure. Mét æ gen n¬i biÕn dÞ alen cã liªn quan víi quiescent A temporary suspension or biÕn ®æi tÝnh tr¹ng sè l-îng. Sù cã mÆt cña reduction in the rate of activity or growth, mét QTL ®ùîc dù ®o¸n tõ lËp b¶n ®å gen, while retaining the potential to resume prior n¬i tæng sè biÕn dÞ ®-îc ph©n chia thμnh activity. Applies particularly to cell division. c¸c thμnh phÇn liªn kÕt víi sè l-îng c¸c See: dormancy. vïng nhiÔm s¾c thÓ t¸ch biÖt. tiÒm Èn Mét sù ngõng hoÆc gi¶m t¹m thêi quantum speciation The rapid formation nhÞp ®é ho¹t ®éng hoÆc sinh tr-ëng, khi of new species, primarily by genetic drift. duy tr× tiÒm n¨ng thu gän tr-íc khi ho¹t møc h×nh thμnh loμi Sù h×nh thμnh nhanh ®éng. ¸p dông riªng cho ph©n chia tÕ bμo. c¸c loμi míi, chñ yÕu do tÝch tô gen. Xem: dormancy. 236 cuèng Trôc ng¾n cña mét b«ng nhá. rachis Main axis of a spike; axis of fern leaf (frond) from which pinnae arise; in compound leaves, the extension of the Rr petiole corresponding to the midrib of an entire leaf. sèng Trôc chÝnh cña b«ng; trôc l¸ c©y d-¬ng xØ (h×nh l¸) tõ ®ã l¸ chÐt xuÊt hiÖn; R genes A class of plant genes conferring trong l¸ c©y hçn hîp, phÇn më réng cuèng resistance to a specific strain (or group l¸ t-¬ng øng víi g©n gi÷a toμn bé l¸ c©y. of strains) of a particular pathogen. Their radiation hybrid cell panel (Abbreviation: primary function is to sense the presence RH). A somatic cell hybrid panel in which of the pathogen and to trigger the defence the chromosomes from the species of pathways in the plant. R genes have been interest have been fragmented by cloned from a number of plant species. irradiation prior to cell fusion. The gen R Mét líp gen thùc vËt chuyÓn tÝnh resultant small fragments of chromosomes kh¸ng cho mét chñng (hoÆc nhãm nßi) greatly increase the power of physical nhÊt ®Þnh cña vËt g©y bÖnh riªng biÖt. Chøc mapping in the species of interest. n¨ng gèc cña chóng lμ c¶m nhËn sù cã b¶n tÕ bμo lai bøc x¹ (viÕt t¾t: RH). Mét mÆt cña vËt g©y bÖnh vμ thóc ®Èy ®-êng b¶n lai tÕ bμo x«ma trong ®ã c¸c nhiÔm mßn b¶o vÖ trong thùc vËt. Gen R ®-îc s¾c thÓ tõ loμi quan t©m ®· ®-îc ph©n nh©n dßng tõ mét sè loμi thùc vËt. m¶nh do tr-êng bøc x¹ tr-íc dung hîp tÕ bμo. Nh÷ng ®o¹n nhá kÕt qu¶ cña nhiÔm R1 The first-generation offspring of a recombinant (genetically modified) s¾c thÓ n©ng cao c«ng suÊt lËp b¶n ®å vËt organism. Not standard terminology. See: chÊt cña nh÷ng loμi quan t©m. T0, T1, and T2. radicle The portion of the plant embryo which develops into the primary root. R1 Con c¸i thÕ hÖ ®Çu tiªn cña sinh vËt t¸i tæ hîp (biÕn ®æi gen).