LCT Gene and Lactose Intolerance Study Notes

LCT Gene Regulation

Activation of Lactase Production

• When DNA segments physically attach to each other, the molecule that transcribes the LCT gene is activated, resulting in lactase production.
• This process signals the ribosome to produce the lactase enzyme.
• If the base sequences of the two DNA segments do not fully interact, transcription does not occur, and lactase is not produced.

Model of LCT Gene Regulation

The model includes:

• Control region one (thousands of base pairs)
• Control region two
• The LCT gene (LCTG)
• Lactase production occurs when all components fit together correctly.

Mutations and Lactose Intolerance

• Question 10 involves understanding how changes in the structure of the LCT gene or its control regions can alter the ability of cells to produce lactase.
• These changes can affect the cells' ability to carry out essential functions in humans who consume milk.
• Mutations in the bases are a key factor.

Base Pairing Example

• Normal base pairing:
  • C binds to G
  • A binds to T
• In lactose intolerance, an incorrect base pairing occurs (e.g., A bonding with C).
• This prevents the LCT gene from being active.

Transcription and Translation

• Question 11 involves:
  • Transcribing DNA into mRNA.
  • Translating mRNA into amino acids.
  • Using the codon chart provided in the student's directions.

Ancestral vs. New Version of the Gene

• Ancestral Version (No Mutation):
  • Bases do not match up correctly.
  • Example: A and C trying to bond.
  • Not all bases are complementary, or a base pair is missing.
  • Transcription is not activated.
  • Lactase is not produced.
• New Version (With Mutation):
  • A mutation occurs where C changes to T.
  • The mutated T can bond with A.
  • All bases are now complementary.
  • Transcription can occur.
  • Lactase is produced.

Transcription Defined

• Transcription is the process of making RNA.