Restriction enzymes, described in Chapter 20, are enzymes that recognize a particular DNA sequence and cleave the

Question:

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 Notl recognizes the sequence
5'_GCGGCCGC-3'
3'-CGCCGGCG-5'
However, if the cytosines in this sequence have been methylated, Notl will not cleave the DNA at this site. For this reason, Notl 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 NotI site.
The arrangement of gene T is shown here.

A salI restriction site is located upstream from the CpG island, and an EcoRI restriction site is located near the end of the coding sequence for gene T. The distance between the NotI and EcoRI sites is 3800 bp. No other sites for SalI, 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.