Answer: D - transcription
In individuals with lactose intolerance, the gene coding for the production of lactase is shut off, leading to a reduced or absent production of lactase. This is due to a phenomenon known as gene regulation, where the expression of a gene can be turned on or off in response to various signals.
In the case of lactase production, the gene is regulated at the level of transcription, which is the first step in gene expression. Transcription is the process by which the genetic information stored in DNA is copied into RNA. The RNA molecule produced during transcription is called messenger RNA (mRNA), which carries the genetic information from the nucleus to the cytoplasm where it is translated into a protein.
In individuals with lactose intolerance, the lactase gene is shut off, meaning that transcription of the lactase gene is suppressed. This occurs due to the binding of regulatory proteins to specific regions of the lactase gene, called enhancers or silencers, which can either activate or repress gene transcription. In lactose intolerance, the binding of repressors to the lactase gene silences its transcription, leading to a reduced or absent production of lactase.
