Chapter 10, Problem 31P

The map below illustrates three alleles in a genome segment. The alleles differ in the number and location of restriction sequences. Restriction digestion and Southern blotting with the molecular probe whose hybridization location is indicated results in detection of a single DNA

band for each allele.

List the size (in kilobases) of DNA bands detected by Southern blotting of restriction digested DNA from organisms with the genotypes ${\text{D}}^{\text{2}}{\text{D}}^{\text{2}}$, ${\text{D}}^{\text{2}}{\text{D}}^{\text{3}}$, and ${\text{D}}^{\text{3}}{\text{D}}^{\text{3}}$.

Restriction $\text{-}$ digested DNA from two organisms is analyzed by Southern blotting. Restriction fragments of $\text{2}\text{.0}$ and $\text{3}\text{.5}$ kb are observed on the Southern blot of one organism, and bands of $\text{2}\text{.0}$ and $\text{3}\text{.0}$ kb are observed for the other. What are the genotypes of these organisms?

Organisms with the genotype ${\text{D}}^{\text{1}}{\text{D}}^{\text{1}}$ are identified by the detection of a $\text{2}\text{.0-}$ kb DNA band on a Southern blot.

Why does this genotype produce a single detectable band, and why are the $\text{1}\text{.0-}$ and $\text{1}\text{.5-}$ kb restriction fragments not detected in Southern blotting?