For forensic inspection, you only obtained red blood cells from an individual and amplified for the D1S80 locus in chromosome 1. Twenty nine different alleles of D1S80 have been identified, and 435 allelic combinations are theoretically possible. Approximately 86% of the population is heterozygous at this locus. You set up a PCR reaction for this locus and ran a DNA gel electrophoresis. What would your expected results be based on the described protocol?

A) You would most likely see no bands

B) You would see more than two bands

C) You would see two bands for the heterozygous while one band for the homozygous

D) You would see two bands for the homozygous while two bands for the heterozygous

I thought the answer was C given that heterozygous people would have two bands, one for each allele, and homozygous people would have one band for their one allele. The answer points to choice A for some reason...

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    $\begingroup$ Good luck retrieving DNA from erythrocytes... $\endgroup$ – LinuxBlanket Jan 10 '18 at 1:05

It is a trick question. Red Blood Cells (RBC) are anucleated in mammals. You are not going to be able to extract anything about chromosome 1 from RBC.

By the way, if you want to know how they got from 29 alleles to 435 possible combinations (in a diploid), you just have to do 29 + 28 + 27 + ... + 1 = 435.

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  • $\begingroup$ Interesting, I thought the same. But given my miniscule knowledge on RFLP, I was guessing that the answer hid somewhere else in the question. Thanks! $\endgroup$ – Felix Hu Jan 10 '18 at 6:54

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