Chapter 7, Problem 27P

A family consisting of a mother ( $\text{I-1}$), a father ( $\text{I-2}$), and three children ( $\text{II-1, II-2, and II-3}$) are genotyped by PCR for a region of an autosome containing repeats of a $10$-bp sequence. The mother carries $16$ repeats on one chromo-some and $21$ on the homologous chromosome. The father carries repeat numbers of $18$ and $26$.

a. Following the illustration style of Figure $7.27c$, which aligns members of a pedigree with their DNA fragments in a gel, draw a DNA gel containing the PCR fragments generated by amplification of DNA from the parents ( $\text{I-1}$ and $\text{I-2}$). Label the size of each fragment

b. Identify all the possible genotypes of children of this couple by specifying PCR fragment lengths in each genotype.

c. What genetic term best describes the pattern of inheritance of this DNA marker? Explain your choice.