Functions/ Dysfunctions-protiein Processing Flashcards
Central dogma of molecular biology
DNA—>RNA—>Protein
What is the purpose of the genetic code
To convert a nucleotide sequence of a gene into an amino acid sequence of a protein using mRNA as an intermediate
(Gene —> protein)
Code can be degenerate (some codons can code for more than one amino acid and some codons do not code for any aa)
Start codon
AUG
Coding for methionine
Stop codons
UAA,
UAG,
UGA
Which point mutation does not cause change in the amino acid being coded
Silent mutation
Which point mutation changes the amino acid in the protein but does not effect the protein function dramatically
Missense mutation
Which point mutation deletes or inserts one or more nucleotides into or out of frame.
Frameshift mutation
Which point mutation changes the codon into a stop codon causing premature termination. Causes the formation of the truncated version of a protein
Nonsense mutation (null mutation)
What disease arises from a missense mutation of the 6th codon in the allele for human B-glowing (subunit of hemoglobin) ?
Changes GAG -> GTG
- valine -> glutamate
- hydrophobic -> negative and hydrophilic
*OPPOSITE
SICKLE CELL ANEMIA
- Hgb starts to aggregate and form rigid rod like structures which causes sickle cell RBC’s
- poor O2 binding capacity of Hgb and Hgb tends to clog capillaries
Large frameshift deletions of the dystrophin gene which leads to defective dystrophin proteins
- causes muscle wasting and eventual wheelchair need
- 1:3,500 males
Duchenne Muscular Dystrophy
Severe form of Duchenne muscular dystrophy is caused by
Out of frame deletions that result in little/no expression of dystrophin proteins
What causes Becker muscular dystrophy
In frame deletions result in the expression of truncated forms of dystrophin. This version is more midl than DMD
*muscle becomes replaced with fat and fibroid
What is the cap on mRNA comprised of
5’ cap is made of guanosine and 3 phosphates
7-methylguanosine cap
What is the tail on mRNA called
Poly(A) tail at the 3’ end made up of adenine
. tRNA serves as an adaptor by having a binding site for both codons in mRNA and amino acids. TRNA matches amino acids to ____ in mRNA
Codons
Describe the structure of tRNA
- cloverleaf structure
- has 2 regions of unpaired nucleotides that are crucial to function
- Anticodon loop where mRNA complementary sequence binds
- 3’ CCA terminal region which binds the matching amino acid [attached is Phe]
It also has a T and D loop
What activates the amino acid that is esterfied to the CCA sequence of tRNA
aminoacyl tRNA synthetase enzyme
- serves as a second genetic code
- each amino acid has its own
- important to maintain fidelity of protein synthesis
Explain how aminoacyl tRNA synthetase functions
- Links amino acid to tRNA by high energy bond
- TRNA the binds to its mRNA codon
This enzyme also catalyze the addition of AMP to COOH end of the amino acid
Where does protein synthesis (translation) occur?
In the ribosome
T/F
Large and small ribosomal subunits assemble together into an active complex in the presence of mRNA
True
Difference between eukaryotic and prokaryotic ribosomal subunits
Eukaryotic - 60S and 40S
Prokaryotic - 50S and 30 S
Important for antibiotic function
What are the 3 sites of a ribosomal complex that are important for translation
- A site. Acceptor site is where the mRNA codon …
- P site- peptidyl site is where aminoacyl tRNA is attached
- E site- exit site is when the tRNA exits the ribosome
What direction does translation occur
5’ —> 3’
What are the 3 steps of translation
- Initiation
- Elongation
- Termination