Week 7 - The Regulation of gene transcription Flashcards
What does genome mean
Entire complement of an organism’s DNA ( all of the chromosomes)
What are chromosome
A thread like structure that helps package the DNA molecule inside the nucleus
What is gene
functional length of DNA that provides the genetic information necessary to build a protein
What is transcription
Producing an mRNA molecule that is complementary to the DNA of a gene
What is transcription regulation
controls the amount of mRNA synthesized from DNA
What are the ways in which transcription can be controlled
- regulatory gDNA sequences
- Chromatin Packaging
- Epigenetic Modification
What does regulatory gDNA sequences use
promoter
enhancers
silencers
What are promoters
a region of genomic DNA where proteins bind and initiate transcription (TATA box)
What are enhancers
A region of genomic DNA where activator bind to increase transcription
What are silencers
A region of genomic DNA where repressors bind to decrease transcription
What are transcription factors
Proteins that can bind to promoters, enhancers or silencers to control the rate of transcription initiation
How are chromatin formed
- Histones which are proteins bind tightly to DNA because more than 1/5 of their amino acids are positively charges (lysine or arginine) and DNA is negatively charged.
- This forms nucleosomes which consist of a DNA strand wrapped twice around 8 histone proteins. Under an electron microscope nucleosomes look like beads on a string.
3 Nucleosomes and the DNA are linked to adjacent nucleosomes forming a chromatin fibre
4 Chromatids coil in loops to become a chromosome. The structural organization of chromatin not only packs a cell’s DNA into a compact form that fits inside the nucleus, but also helps regulate gene expression: (expansion vs condensation)
What is the structure of a nucleosome
DNA strand wrapped twice around 8 histone proteins. Under an electron microscope nucleosomes look like beads on a string.
What are the 2 ways which the structure of chromatin is regulated
- acetylation of histone tails
- DNA methylation
How does the acetylation of Histone tail regulation chromatin
the acetylation of histone tails (adding acetyl groups) by histone acetyltransferases (HATs) promotes the loose chromatin structure - permitting DNA transcription
The de acetylation of histone tails by histone deacetylase (HDACs) remove an acetyl group promoting a compact chromatin structure which decreases DNA transcription
How does DNA methylation regulate the structure chromatin
No methylation allows transcription factors to bind to the gene “turning it on” and activating the chromatin - increasing gene expression
Methylated DNA reduces the binding of transcription factors to the DNA “switching it off” promoting chromatin compaction leading to decreases gene expression
