Gene Expression Flashcards
Promotor region
Indicates where the gene starts on the chromosome
Transcription factor
- binds to promotor region
- Helps RNA polymerase to bind to DNA strand
RNA polymerase
Converts double-stranded DNA to single strands by breaking hydrogen bonds
Adds complementary RNA nucleotides to the 3’ end based on complementary base pairing rule
What happens in initiation
Transcription factor binds to promoter region: helps RNA polymerase to bind to DNA strand
RNA polymerase unwinds double stranded DNA by breaking hydrogen bonds
What happens in elongation
RNA polymerase at complementary nucleotides to the three prime end
What happens in termination
RNA polymerase
Reaches termination sequence
Releases the DNA (which reanneals)
Releases primary RNA transcript
What is the function of transcription
To create a primary RNA transcript
Gene expression stages
- Transcription
- mRNA processing
- Translation
Introns
Exons
Introns - NON coding regions
Exons - CODING regions (want to keep)
What happens in splicing
Introns are removed
Exons are joined together
What is the function of 5’ caps and poly-A tails
To protect the gene
Prevents gene from getting broken down in the cytoplasm
5’ methylated caps
GGGGGG…
Added to 5’ end
Poly-A tail
AAAAAAA….
Added to 3’ end
What is the function of mRNA processing?
To produce the final RNA transcript
- remove introns
- add 5’ cap and poly-A tail
What happens in translation
RNA acts as a template to make protein
mRNA is read _____
5’ to 3’
3 letters at a time (CODONS)
Each codon…
Codes for 1 amino acid
Made up of three nitrogenous bases (AUG)
What are the two types of ribosomes
Free ribosomes
- Cytoplasm
- Make proteins for use inside the cell
Bound ribosomes
- Rough ER
- Make proteins for use outside the cell
Codons are…
Redundant (many different codons can code for the same amino acid
Not ambiguous - each codon can only code for one particular amino acid
Non-overlapping
Continuous
Stages of translation
- Initiation
- Elongation
- Termination
(Same as Transcription)
Translation:
What happens in initiation
Ribosome attaches to start codon located on 5’ end
Allows tRNA to read the start codon to bring amino acid (AUG, Methionine)
What does tRNA do?
Carries an amino acid
Reads codons of mRNA using anti-codons
mRNA has ____
tRNA has ____
codons
anticodons
What do the ribosomes do
Hold everything together
Hold mRNA, tRNA and polypeptide bonds
What happens in elongation
TRNA reads codons of mRNA using anticodons and adds complementary nucleotides
Ribosomes make peptide bonds between amino acids to form polypeptides
What happens in termination
Ribosome reaches Stop codon
Released everything:
Releases mRNA, tRNA and polypeptide (protein)
Translation complete polypeptide formed
What are the 2 components that make up ribosomes
Small subunit
Large subunit
Both made of proteins and rRNA
What is the function of translation?
To read the final RNA transcript and make protein
To put the amino acids in the correct sequence and join them to form polypeptide chains
Stop codons
UAA, UAG, UGA
Found at the end of mRNA sequence
Coding strand
Strand that is NOT transcribed
tells us what the mRNA will look like
Template strand
Strand that IS transcribed
Strength that acts as a template
Why don’t we need helicase in Transcription?
RNA polymerase can break hydrogen bonds as well as add RNA nucleotides
In DNA replication…
In transcription…
Both strands act as templates
Only one strand undergoes transcription / Only one strand acts as a template
