Furrow, C. Lee

English

OSU Journals (Oklahoma State University)

OKLAHOMA ACADEMY OF SCIENCE 49XXIII. A PRELIMINARY REPORT ON THE GENETICSOF A RED SPOTTED SEX LIMITED MUTATIONBRUCHUSClarence Lee Furrow.From the.- Zoological Laborator)' of the lJni\'(~rs:ty of Oklahoma.Coptribution No. 20, Second Series.This report is concuncd with the genetic behavior of a 'sexlimited' mutation which ocxurrcd in a stock of culture of Bruc1lus.th~ four·spotted cowpea weevil.In the wild or normal stoclc tan is the.common body color. Thefemale of the wild type carries four black spou, two on eache:ytrum. The inale is. lflsconspicuous than the female, as he is'pluch smaller in size and does not have .potted elytra; however,the f~o.rs Jor body .ftOIOr and e)ytra pattern are _. carried by the~ even though they ate DOt manifested ~icaUy. , ' ...During'tht year of 19~1, while invempting a Hock-culture of50 THE·UNJVERSITY OF OKLAHOMABmlMu 'pure fo,· tan, Dr. ]. K.' Breitenbecher observed a femalewit!(red· body color; This mutant female was 'mated with a normaltan male by him and· inbred until a ma6S culture pure for red was ob-taiiieCL In this race of insects the female has the usual four blackspots· of the wild type, and the red body co!or of the mutation, whilethe male is a tan phenotype but· a red genotype.On September 22, 1921, a female was found in a mass culturepure for red body color which had four red' spots instead of thefetUr'bJa'ck spots. This mutant female with red body color and red.potted efytra was mated with a male that was pure for red. Afterseveral matings for homologous mutants, a culture was obtainedthat was pure for both red body and red spots.It is of special interest to note that this character is sexlimited, that is, manifested only in the fema~e. The male of this. stTain is pure for the same factors, but every male appears tan in. body color and has no elytra pattern visible. This kind of sexualdimorphism is known as 'sex limited,' and is often called a secondarysex ·character. As a result of this we ha,'c two different types ofinseds produced. \The factor symbol for red spots may be represented by (55)arid' that of blade spots by (ss). Then by crossing a female purefor red spots (55) with a male pure for the same (55) the result·ing offspring will everyone be pure for red spots (S5).ExperimentsOne female pure for red spots was mated with a spotless ma~e,pure for black spots. The resulting female offspring were all redspotted. Sufficient data has been obtained to show that the normalblack spots is a Mendelian recessive to the red spotted mutation; inotller words the mutation is a complete dominant to the blade spotsof the tan wild type.A mutant female, pure for red spots was bred to a mate purefor red spots. No blac" spotted females were obtained. but ten redspotted females.and nineteen tan males carrying (S5) were obs~rved.When a red' spotted female (55) is mated with a non-spottedmale (IS) carrying black spots, their female'offspring were all I'Mspotted (Ss). but the males were all 'Den-spotted:, ,.,- 9, crouinlr the .Ft"es'and females from the .abOve esperi-ment (both of whidl··,were heterozygous ($5) fOr red and· Uaclr'POt,> tbefollowina·F. o"'ril~arwereobtained: hftnly-nine redIpOtte4 females -.whoIe .·~c;onstitutioo may be repl'e$~t~ at.:(SS, 51. "and as)llme' b1adI: ipottecI femal~ (sa) aad twe'1lb-hrO1lOIl~' tan·..... ·(SSt si. sS,aaclD).saIee' the·ftdsootteif~ is' dOmiaantto'· tIle'*k for theOKLAHO}dA ACA'DEMY OF SCIENCE -51females, one fourth will be pure for red spots, one-bali will' heheteroJygous, for red and b!ac~ but'will appear, as red .spoU, andone-fourth will be homozygous for black spots. This is confirmedby the exper;mental results of the cross. All the males frGm thi~mating were non-spotted in appearance," but each bear the ~amcgentiC factors of tlte' garnett's as manifested for the above fem~les.A hetet:ozygous female (Ss) was mated with a homoxy~o:.;sblack male (ss). This is really a back cross of a female manifc$t.ing' red spots, an~ whose gametes carry both red and black spotswith the F. male 'that was pure for black spots. The offspringfrom this cross were ten red spotted females (Ss), eleven blackspotted females (ss) and twenty tan non-spotted males (Ss and 55).This result conforms'to the theoretical expectation of such a cr05S,in that we Itave cibt~iJ1ed the 1 :I :2, sex limited ratio.The reciprocal cross demonstrates a similar inheritance. Ahomozygous black spptted female (ss) was mated with a hetero%y-gous non-spotted tan male (55). Six hlack spotted females (ss).four red spotted females (55), and eight non-spotted tan males(55 and 55) were the offspring from this crou. fJere again thesex limited results may be interpreted as a 1: I :2, ratio. Obviouslythe results of this eros!' show one-half of the females are redspotted and heterozygous, and one-half arc black spotted andhomozygous, and the offspring obtained while small in number, art"in line with the theoretical expectation.The data presented in this paper are not sufficient to permitany final conclusions, however, a fundllmental genetic behaviorwhich is in kCfping with sex limited inheritance, is demonstrated.More data are beiug accumulated, and an of it confirms so far theabove interpretation. .ConclusionThese experiments show that red spotting is due to a mutation;that is a complete dominant to the black spots in die tan wild type;and that the particular kind of sexual dimorphism exhibited hereis in accordance with the behavior of the 'sex limited' type of in-heritance. '

A Preliminary Report on the Genetics of a Red-Spotted Sex Limited Mutation in Bruchus

https://ojs.library.okstate.edu/osu/index.php/OAS/article/download/2166/1867

A Preliminary Report on the Genetics of a Red-Spotted Sex Limited Mutation in Bruchus

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