Genetics: Analysis and Principles 5th Edition by Robert Brooker

Exercise 42

Restriction enzymes, described in Chapter 20, are enzymes that recognize a particular DNA sequence and cleave the DNA (along the DNA backbone) at that site. The restriction enzyme known as Not I recognizes the sequence
5 -GCGGCCGC-3
3 -CGCCGGCG-5
However, if the cytosines in this sequence have been methylated, Not I will not cleave the DNA at this site. For this reason, Not I is commonly used to investigate the methylation state of CpG islands.A researcher has studied a gene, which we will call gene T , that is found in corn. This gene encodes a transporter involved in the uptake of phosphate from the soil. A CpG island is located near the core promoter of gene T. The CpG island has a single Notl site. The arrangement of gene T is shown here.
a.
A Sal I restriction site is located upstream from the CpG island, and an Eco RI restriction site is located near the end of the coding sequence for gene T. The distance between the Sal I and Not I sites is 1500 bp, and the distance between the Not I and Eco RI sites is 3800 bp. No other sites for Sal I, Not I, or EcoRI are found in this region.Here is the question. Let's suppose a researcher has isolated DNA samples from four different tissues in a corn plant. These include the leaf, the tassel, a section of stem, and a section of root. The DNA was then digested with all three restriction enzymes, separated by gel electrophoresis, and then probed with a DNA fragment complementary to the gene T coding sequence. The results are shown here.
a.
In which type of tissue is the CpG island methylated Does this make sense based on the function of the protein encoded by gene T