CSI Wildlife: Frequency Primer

Click & Learn

Student Supplement

Let’s now apply these formulas to some real data. Look at the gel shown

on the screen. It represents a four-marker genetic profile for an elephant

in a different population. The relative frequencies for the alleles shown

are summarized in the table to the right.

9. Why is there only one frequency for the alleles for the FH19 and FH71

STR markers, but two frequencies for the alleles for the FH127 and

FH67 markers?

10. The elephant profiled here is homozygous for an allele of the FH71 marker. As shown in the table, this allele

has a relative frequency of 0.09. Based on the formula in Question 6, the probability of an elephant from this

population having the profiled elephant’s genotype for the FH71 marker (in other words, for being

homozygous for the same FH71 allele) is (0.09)

2

= 0.008.

This elephant is also homozygous for an allele of the FH19 marker. What is the probability of an elephant

from this population being homozygous for the same FH19 allele? Show your work.

11. The elephant profiled here is heterozygous for the FH67 marker; it has two different alleles for this marker

with relative frequencies of 0.1 and 0.24. Based on the formula in Question 7, the probability of an elephant

from this population having the profiled elephant’s genotype for the FH67 marker is 2(0.1)(0.24) = 0.048.

What is the probability of an elephant from this population having the profiled elephant’s genotype for the

F127 marker? Show your work.

12. Using the probabilities from Questions 10 and 11, calculate the probability of an individual from this

population having this exact four-marker genetic profile. Show your work. (Note that the answer in the Click

& Learn was calculated without rounding the probabilities from Questions 10 and 11. You may get a slightly

different answer if you round these probabilities.)

of allele(s) shown