Unformatted text preview: 118 Chapter 4 • Eukaryote Chromosome Mapping by Recombination Morgan’s testcross results were as follows (listed as the gametic classes from the dihybrid): pr 1 ? vg 1 1339 pr ? vg 1195 pr 1 ? vg 151 pr ? vg 1 2839 Obviously, these numbers deviate drastically from the Mendelian prediction of a 1:1:1:1 ratio, and they clearly indicate an association of certain alleles. The alleles associ- ated with each other are those in the two largest classes, the combinations pr 1 ? vg 1 and pr ? vg . These are the very same allele combinations introduced by the original homozygous parental flies. The testcross also reveals an- other new finding: there is approximately a 1:1 ratio not only between the two parental combinations (1339 < 1195), but also between the two nonparental combina- tions (151 < 154). Now let’s look at another cross Morgan made using the same alleles but in a different combination. In this cross, each parent is homozygous for the dominant allele of one gene and the recessive allele of the other. Again Fof one gene and the recessive allele of the other....
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.
- Spring '08