Chapter 10, Problem 24P

Summary Introduction

To analyze:

Plants of a particular species can either have the dominant wild-type phenotype, tall (T), or the recessive phenotype called dwarf (D). Consider that genetic analysis has identified the stature gene, and DNA analysis of tall plants yields a DNA fragment of $7.5$ kb corresponding to a portion of the gene. The wild-type gene map is shown, along with an autoradiograph showing DNA restriction fragments from a normal parental plant (T; lane $1$), a tall plant that carries a copy of the mutant allele (T; lane $2$), the two DNA fragment patterns observed in tall progeny plants (T; lanes $3$ and $4$), and the DNA fragment pattern seen in dwarf plants (D; lane $5$).

Using this information, answer the following:

1. Propose two mutational events that could cause the small DNA fragment that represents the mutant allele.

2. In northern blot analysis of mRNA, what mRNA differences would you anticipate for your two proposed mutational mechanisms?

Introduction:

The wild type dominant gene produces tall plants, and recessive genes are responsible for production of dwarf plants. The wild type gene gives a fragment of length around $7.5$ kb. This gene codes for the trait – tall plants. On the other hand, mutant allele gives a fragment of length around $4$ kb. It codes for dwarf trait. Organisms that are homozygous for DNA sequence, the same restriction fragments are produced. On the other hand, heterozygous organisms have different DNA sequences and produce different restriction fragments.