1 2 3 4 5 6 7 8 9 10 423 bp 322 bp 234 bp 198 bp 11 12 13 14 15 16 17 18 19 20 423 bp 322 bp 234 bp 198 bp 21 22 23 24 25 26 27 28 29 30 423 bp 322 bp 234 bp 198 bp 31 32 33 34 35 36 37 38 39 40 423 bp 322 bp 234 bp 198 bp A. What is the arrangement of the se two STSS in this individual? B. What is the map distance between STS-1 and STS-2?
The distance between two molecular markers that are linked along
the same chromosome can be determined by analyzing the outcomes
of crosses. This can be done in humans by analyzing a family’s
pedigree. However, the accuracy of linkage mapping in human
pedigrees is fairly limited because the number of people in most
families is relatively small. As an alternative, researchers can
analyze a population of sperm, produced from a single male, and
compute linkage distance in this manner. As an example, let’s
suppose a male is heterozygous for two polymorphic STSs. STS-1
exists in two sizes: 234 bp and 198 bp. STS-2 also exists in two
sizes: 423 bp and 322 bp. A sample of sperm was collected from
this man, and individual sperm were placed into 40 separate tubes.
In other words, there was one sperm in each tube. Believe it or not,
PCR is sensitive enough to allow analysis of DNA in a single sperm!
Into each of the 40 tubes were added the primers that amplify STS-1
and STS-2, and then the samples were subjected to PCR. The
following results were obtained
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