Transcript Transcription factors - Raleigh Charter High School

Topic 1: Control of Gene
Expression
Jamila Al-Shishani
Mehran Hazheer
John Ligtenberg
Shobana Subramanian
Youtube Video
Gene Expression Video
• http://www.youtube.com/watch?v=OEWOZS_JTgk&feature=
related
Basic Concepts
• Promoter- a DNA sequence where RNA polymerase binds
(with the help of transcription factors) and starts
transcription.
• Transcription factors - a protein which binds to DNA at
specific sites so it can regulate transcription. involved in
initiation stage of RNA transcription.key to determining
where the DNA becomes unzipped.
o general transcription factors
o upstream transcription factors
o inducible transcription factors
Basic Concepts cont.
• Enhancer - specific DNA sequences which bind with
activators to enhance transcription.
• Activator - transcription factor which binds to an enhancer
and stimulates transcription of gene. help position of the
initiation complex on the promoter.
• TATA Box - the DNA sequence which indicates where the
DNA can be read and decoded.
• RNA Polymerase - enzyme which catalyzes the synthesis
of RNA from DNA template
• Distal Control Elements- control elements far from the
promoter
• Proximal Control Elements -control elements which are
close to the promoter
Basic Concepts cont.
• Differentiation- the divergence in form and function as cells become
specialized during an organism's development.
• Cellular differentiation in eukaryoteso Highly specialized cells (ex. those in muscle or nerve tissue) only express a
small fraction of their genes.
o A typical human cell only expresses 3-5% of its genes at any given time.
The transcription enzymes must find the right genes at the right time.
o Most control of gene expression happens at transcription, where the
enzymes copy only the genes needed at the time.
Basic Concepts cont.
• The 3' end is determined by the RNA sequence encoded by the terminator at
the end of the last exon.
• RNA processing enzymes add a 5' cap and a 3' Poly A tail to the primary
transcript.
• Exons are nucleotides which are coded for a protein.
• Introns are nucleotides in between the exons which do NOT code for
proteins.
Basic Concepts cont.
•
•
•
•
•
•
•
•
•
Activators (a transcription factor that binds to a enhancer) binds to an enhancer (distal control element) to
start Transcription
The DNA then bends to bring the enhancers closer to the promoters. Other transcription factors and RNA
Polymerase are nearby
Protein-binding domains on activators attach to certain transcription factors and help them form an initiation
complex on the promoter
DNA is unzipped by helicase separating the two nucleotide chains
RNA Polymerase reads the DNA from the 3 prime end to the 5 prime end and synthesizes RNA in the 5
prime end to the 3 prime end
Alternative splicing is an example of regulation in which different mRNA molecules are produced
depending on which RNA segments are treated as introns and which are treated as exons
The ribonucleotides are then read in a series of nucleotide triplets called codons. Each codon codes
for a separate amino acid
tRNA then brings an amino acid for each codon by using a anti-codon to distinguish
After translation, posttranslation modification adds functional groups on the protein to increase it
usefulness
Five Words
• Transcription
• Translation
• Gene Expression
• RNA synthesis
• Codon
Review Questions
1. What binds to the activator to start transcription? –enhancer
2. What is differentiation? –the divergence of cells to become
specialized
3. What happens to the polypeptide after translation? –
functional groups get added and it folds to become a functional
protein
4. What are removed from the mRNA? –introns
Review Questions cont. (Mehran)