Topic 2 Molecular Genetics: Regulation of Eukaryotic Gene Expression

Question 1

• Repressors and enhancers/activators that influence RNA polymerase attachment to the promoter region.
• Utilizing the presence or absence of activators allows for cell type-specific transcription (for example: a liver versus a lens cell transcribe different genes)

Answer 1

1. Regulatory Proteins

Question 2

• Involves regulation at the chromosome level, which we briefly touched on in previous sections.
  i. Methylation of histones - results in tighter packing that prevents transcription
  ii. Acetylation of histones - uncoils chromatin, encouraging transcription
  iii. Direct DNA methylation - epigenetic control of DNA that can be inherited and usually leads to lower expression

Answer 2

2. Nucleosome Packing

Question 3

• Methylation is also used in X- inactivation and on DNA bases to repress gene activity. Also, while histone methylation usually prevents transcription, it can sometime activate it as well

Answer 3

Note

Question 4

i. Noncoding RNA (ncRNA) plays a role in controlling gene expression as well! Some are even involved in chromatin modification.
ii. Micro RNA (miRNA) - single stranded RNA molecules that bind to complementary RNA sequences and either degrade the target or block its translation
iii. Short interfering RNA (siRNA) - function similarly to miRNA, aside from a subtle difference between the precursors.
i. In both cases, double stranded RNA becomes single stranded and then carries out its function.
ii. RNA interference (RNAi) is the blocking of gene expression using siRNAs

Answer 4

3. RNA Interface

Question 5

• 97% of human DNA does not code for protein product, but rather for non-coding DNA
  i. Non-coding DNA includes regulatory sequences, introns, tandem repeats, and repetitive sequences that are never transcribed
  ii. Tandem repeats are abnormally long stretches of back-to-back repetitive sequences within an affected gene (e.g., Huntington’s).

Answer 5

4. Human Genome