Question

2. Short tandem repeat polymorphisms (STRPs) are genetic markers that have multiple alleles per locus in the population. Since there are more than 2 alleles for a STRP, we have to use numbers rather than A/a or +/- to indicate their identities. The following pedigree corresponds to the genotype table below. The order of alleles listed for each genotype does not indicate anything about haplotype (e.g. "1,2" could mean 1 is on the maternal chromosome and 2 is on the paternal chromosome, or vice versa) STRP-A 1,2 1,3 2,3 1,2 3,3 1,3 1,3 Individual 1-1 1-2 STRP-B 2,2 1,2 2,2 1,2 3,3 1,3 2,3 2,3 STRP-C 2,3 1,3 2,3 1,2 3,4 STRP-D 2,3 2,2 1I-3 2,4 2,4 lI-3 Just looking at the first 2 generations, what are the haplotypes of I-1, 1-2, Il-1 and II-2? HINT Use different colored highlighters or different shapes to mark which alleles came from each parent. a. b. Given your answer to part 1, deduce the haplotypes of the third generation. c. Where did a recombination event occur in this family? (i.e., crossing over between which markers, in a meiosis in which parent that resulted in which haplotype in a particular child?)

Answer 1

The haplotypes are given besides the respective individuals in the pedigree. The haplotypes are deduced from the inheritance of the markers together from one parent which shows that they should be present together in one of the homologous chromosomes in the parent. As suggested different colors are used to show this.

33세세 33세세 3 3 1112 3233 33센세 1222 1112 2 2 2 1 1112 1 3233 1231

A recombination event must have occurred in II2 of this family between STRP A and STRP B. This resulted in new combination. The recombined haplotype is inherited by III2. As can be seen in the figure, the recombined chromosome contain markers with two different colors.