Question

The following is a diagram of the LCT (lactase gene) gene regulation system in humans. When the LCT gene is transcriptionally active, the cell produces the enzyme lactase, which is needed to digest the lactose in many dairy products. Based on what you know about enhancers and promoters from your reading, predict how the following scenarios might influence LCT gene expression and thus lactase production in cells:

The enhancer sequence is inverted, but remains intact so that Oct1 still binds to it.

The promoter sequence normally includes a CAAT box about 80 bases pairs prior to the start site, but this promoter element is mutated.

In the case of LCT (lactase), one of the many factors involved in transcription regulation is the activator Oct1 that contributes to increased LCT expression. Oct1 TA TFRNA LCT gene -13910 enhancer promoter Start of transcription Oct1 binds to an enhancer region located 13910 bp upstream of the lactase gene (LCT), general transcription Octl Coactivators ofactors (TF) bind to the promoter region Pol LCT gene at about 80 bp upstream of LCT Figure 6. Regulation of the LCT gene by Oct1. Image modified from: Schultheis, PJ. and B.V. Bowlling, 2011, Analysis of a SNP Linked to Lactase Persistence, BAMBED 39(2): 133-140.

The enhancer sequence is mutated to increase its binding to Oct1.

Answer 1

Congenital Lactase deficiency or Congenital alactasia can be caused by Nine LC Gene mutation. In this disorder infants are unable tbreak down the Lactose, Generally called Lactose intolerence. The same is found in adulthood due to gradual decrease in activity or expression of the LCT gene.

Lactose intolerance in adulthood is caused by gradually decreasing activity (expression) of the LCT gene after infancy, which occurs in most humans.

Activators are helpful in initiating transcription by binding to RNA Polymerase and other enzymes used in transcription. This type of TF therefore increases the expression of a gene.

A Mutation at the enhancer site located 13190 bp upstream of the gene increases the binding of Oct1, which attracts more general transcription gactors to the Lactase gene through out the indicidual adult life. This prevents the decrease transcription of the gene and results in a steady and proper level of Lactae and a retained ability to digest lactose in milk.