Types of Mutations
Define insertion/deletion mutations. These are classified generally as __ mutations. Why are they classified this way?
Insertion - an extra base is added
Deletion - a base is lost/deleted
Frameshift
5' TAC ACC 3'
What is the complementary base pairing in DNA replication? What direction will you write it/why?
3' ATG TGG 5'
DNA is antiparallel
What is the difference between the template strand and the coding strand?
Template strand - the strand that gets copied; what you start with
Coding strand - the strand that looks just like the mRNA strand; the U's are T's in this strand
What is the main mechanism involved in post-transcriptional control? How does post-transcriptional control generate protein diversity?
Intron splicing; done by the spliceosome; alternative splicing - exons may be included or removed - introns may be included
What is meant by the common description that DNA replication is semi-conservative?
One strand will be from the original template molecule
One strand will be newly synthesized
Define a missense mutation. Give an example.
Missense - a substitution that changes the amino acid
Glu --> Val in sickle-cell anemia
Replication involves __ (molecule) into --> __ (molecule)
DNA --> DNA
3' GGC AAT TAC CTC 5'
Transcribe this into mature RNA.
Use the codon table to translate into amino acids.
5' CCG UUA AUG GAG 3'
-- -- MET GLU
What are some covalent modifications involved in post-translational modification? Based on your answer (there are many right answers), what is the function of this modification?
Acid/base - behavior of the amino/carboxyl groups in physio. pH can activate/inhibit protein function
Hydrolysis - enzymatic hydrolysis breaks peptide bonds/can shorten an immature protein and/or remove a localization tag
Acetylation - histone acetylation promotes transcription
Phosphorylation - addition of Pi by kinase allows cellular work/transfer of E
Glycosylation - covalent addition of carb chain to membrane-bound proteins
What was the main outcome of the Meselson-Stahl experiment?
To test which model of DNA replication (conservative, dispersive, or semiconservative models were accurate) - demonstrated evidence for semiconservative model
Define a nonsense mutation. Give an example.
Stop codon; changes the amino acid to a stop codon
Example: any of the 3 stop codons
Replication occurs in the __ --> __ direction. This means that nucleotides are added to an exposed __ __ __. Explain why this makes sense.
5' --> 3' direction
3' hydroxyl group
(Penelopi pull up image)
3' GGC AAT TAC CTC 5'
What is so special about GGC AAT above in terms of its positionality in the mature mRNA strand?
Transcribe into mRNA --> use codon chart --> PRO LEU --> but they are upstream of AUG start codon so they will not be incorporated into final amino acid strand
Why did the Meselson-Stahl experiment utilize N?
Nitrogen is a key component of DNA and can exist as a heavier 15N or a lighter 14N
Silent - a substitution that does not change the amino acid
Example (anything that doesn't change!) (reference codon chart)
Where does replication occur?
Nucleus
Where does transcription occur (in eukaryotes)?
Nucleus
What were the molecular results of the Meselson-Stahl experiment?
The results after two divisions supported the semi-conservative model of DNA replication
Missense, nonsense, and silent mutations are generally classified as __ __. Why?
Point/substitution mutations - because one base is substituted for another
Where does translation occur? (Be specific!)
On ribosome located in cytosol on the EPA sites