Gene mapping from two point cross
Two point testcross involves two gene loci. t is used to determine the recombinant frequency between the two linked genes. The distance between the two genes determine the chances of crossing over during cell division and hence recombinant frequency can be determined.
The two genes P and Q can be- u P and Q are present extremely close- crossing over cannot occur between them and hence the genes are inherited together so 100% parental types are formed with no recombinants P and Q are present at some distance and not very close- crossing over can occur between the gene loci and can lead to the generation of 0-50% recombinants
uP and Q are present very far from each other- crossing over definitely occur between the gene loci and lead to the generation of 50% recombinants and 50% parental types.
Q A cross is made between a white eyed-miniature winged female with a red eyed-normal winged male of Drosophila melanogaster. Further crossing of Fl female offspring from this cross with a white eyed-miniature winged male fly gave 95 white eyed-normal winged, 102 red eyed-miniature winged, 226 red eyed-normal winged and 202 white eyed-miniature winged offspring in F2 generation. What is the percent frequency of recombination between the two genes? (A) 20.11 (B) 31.52 (C) 49.10 (D) 34.12
numbe ulhite e ed -nonmal Recombinants Red eyed - miniatu o2 ingedl Red eved- nomol 2G winqedl anenta Wh le eyed-miniature 202 lNinqe
Xloo IbJu otal no 95 102 x 100 9S +102 t 226 +202 x loo 31.52 625
Que- A true breeding plant with violet flowers and round seeds(VVRR) was crossed with true breeding plants with white flowers and wrinkled seeds(vvrr). The F1l offsprings(VvRr) were then test crossed with plants with white flowers and wrinkled seeds. The offsprings resulted from this cross is as follows Calculate the percentage recombinant frequency between two genes
Phenotype Number Violet flowers, round seeds White flowers, wrinkled seeds Violet flowers, wrinkled seeds White flowers, round seeds 65 75 27 13
Que- a true breeding maize plant with golden and large kernels(YYSS) was crossed with true breeding maize plant with yellow and small kernels(yyss). The F1 offspring having YySs genotype was testcrossed to yyss. The offsprings produced wee as follows. Find the percentage of recombinants between two genes
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