Overview
What do genes code for?
polypeptides (proteins) or RNA molecules
What are the three types of RNA involved in protein synthesis and what do they do?
mRNA binds to a ribosome
tRNA recognizes the start codon of the mRNA
rRNA forms the ribosome structure
What are the three steps of transcription?
1) Initiation
2) Elongation
3) Termination
What happens during translation(general)?
mRNA is translated into a polypeptide
True or False: RNA processing only happens in eukaryotes
True
What is gene expression? What are the two major steps?
Gene expression is a two-step process where a DNA nucleotide sequence is converted into an amino acid sequence. The two steps are transcription and translation.
What is a codon?
three consecutive bases (triplets) that specifies one amino acid
also have start (AUG) and stop (UAA,UAG,UGA) codons
the codons on the mRNA determines the primary structure of the protein
Where does RNA polymerase bind to DNA during initiation?
the promoter site
this is where it unwinds the helix and begins transcription
What is a ribososme composed of?
rRNA and protein; has large and small subunits
What type of mutation is a change in one pair of DNA nucleotides?
a base-pair substitution or point mutation
What is being formed in transcription? what about translation?
Transcription is going from DNA to RNA and translation is going from RNA to protein.
What is one important fact about tRNA?
The anticodon region is complementary to the mRNA codon and specifies which amino acid it will carry.
Summarize elongation
RNA nucleotides are added by RNA polymerase to the 3' end of the growing mRNA strand
How are polypeptides formed?
Peptide bonds form between amino acids
What is the function of the cap?
üprevents mRNA degradation and helps the transcript bind to a ribosome later on
What is the Central Dogma of Biology?
DNA->RNA->Polypeptide(Proteins)
The ribosome has a large subunit and a small subunit. Which end of the mRNA strand does the ribosome attach to and which direction does it move? Also. what are the three sites?
it attaches to the 5' end and moves in the 5'-3' direction
E, P, A
What causes transcription to end?
Transcription ends when the polymerase reaches the termination sequence aka the stop codon.
then RNA polymerase separates from the DNA template strand
What happens when the polypeptide is released?
It is modified and folded into a functional protein
What are the important features of the genetic code?
Degenerate – an amino acid can be coded for by more than one codon.
Has one start codon and three stop codons to ensure the correct reading frame.
Universal – the code applies across all living organisms, with a few small exceptions, from bacteria to humans
Contrast DNA replication with Protein Synthesis.
I don't have an exact answer in mind, just discuss it.
What is the job of RNA polymerase?
It adds the RNA nucleotides to form the mRNA strand.
What all occurs RNA processing?
A 5’ cap is added to the 5’ end
A poly-A tail is added to the 3’ end
Splicing: introns are cut out and exons are spliced together.
True or False: Translation can stop and end anywhere on the mRNA sequence
False: It can only start when it sees the start codon(AUG). It can only end at one of the three stop codons(UAG, UGA, UAA)
Go from template strand to the Amino Acid sequence
3' TCGACCTACGTTTTTATT 5'
mRNA: 5' AGCUGGAUGCAAAAAUAA 3'
5' AGC-UGG-AUG-CAA-AAA-UAA 3'
AUG=Start
UAA, UAG, UGA=Stop
AA: Met-Gin-Lys-Stop