Molecular Microbiology 8-11 Flashcards
What is tRNA?
- tRNA is specific to recognizing each amino acid
- Binds with ATP to an amino acid-producing AMP
- its anticodon loop binds to the complementary codon on mRNA
- the 3’ acceptor arm ester bonds with the carboxylic acid of an amino acid and carries it to the ribosome site
What is mRNA?
-During transcription an RNA Polymerase reads DNA and creates a complementary single RNA strand called mRNA.
-mature mRNA after splicing of exons determines the sequence of amino acids to be formed as a protein
What is rRNA?
-non-coding RNA that forms the large and small subunits of the Ribosome
-In the larger subunit, it forms the peptidyl transferase, an ENZYME, that catalyzes the peptide bond formation between amino acids in protein biosynthesis (23S rNA). It also allows tRNA hydrolysis to release the protein from the tRNA and Ribosome. (can be targeted by antibiotics so bonds can’t form)
23 sRNA
RNA that acts as an ENZYME, not a protein, to catalyze peptide bond formation
Initiation
-at AUG start codon major and minor rRNA subunits combine into a ribosome
-Binding site upstream from start codon at GTP cap
-The initiator tRNA, carrying the first amino acid (METhionine), binds to the P-site (peptidyl site) on the Ribosome forming Initiation Complex
Anticodon
-Arm of tRNA clover structure that binds to 3 complementary bases of mRNA
-Wobble Hypothesis: binds more loosely to 3rd codon allowing one tRNA to bind to more than one codon and code for the same amino acid
Anticodon
-Arm of tRNA clover structure that binds to 3 complementary bases of mRNA
-Wobble Hypothesis: binds more loosely to 3rd codon allowing one tRNA to bind to more than one codon and code for the same amino acid
Elongation
-the incoming tRNA anticodon binds to the A-site of the codon next to the P-site
-The ribosome moves along the mRNA in the 5’ to 3’ direction allowing the amino acids to be linked by peptide bonds in the proper direction
-mRNA sifts down a codon and the empty tRNA moves out of the P-site to exit via the E-site
Termination
-Once the stop codon reaches the ribosome A-site, Release Factors (RF) cleave polypeptide from tRNA by adding a water
-Ribosome dissociates
GTP
Used in translation to form peptide amino acid chains in elongation and other steps
What is a Suppressor?
-A mutant tRNA that recognizes when a mRNA is wrong and if there is a stop codon brings an amino acid anyway.
-Compensates for original mutation
What are the Parts of the Amino Acid and what give it it’s properties?
(Amino Group, Carboxylic Acid = all have it) and R-Group (changes based on amino acid and can be polar, np ect.)
Gram Positive
Stain Purple, 1 membrane with thick membrane
Stain gets stuck in the thick cross-linked peptidoglycan cell wall
Gram Negative
Stain Pink, 2 membranes with thin peptidoglycan. Ethanol decolorizer breaks down thin membrane so violet-iodine crystal can escape
Reversion
A mutation in the DNA portion that corrects for a mutation
-DNA changing (phenotype might not change back bc epigenetics)
Revertant
strain for mutation that restores original phenotype
Same-site: mutation at same site as original
Second-site: mutation at different site
Truncated Protein
An amino acid chain that has been shortened because of a mutation - usually nonsense
Silence Mutation
A point mutation in the DNA that doesn’t change the amino acid chain produced -nucleotide different, but codon codes for same amino acid
Nonsense Mutation
A mutation that changes an amino acid to a stop codon so the protein chain ends early - point
Missense Mutation
A mutation that causes one of the amino acids to be changed in a change - point
Frameshift Mutation
An insertion or deletion of a nucleotide will shift the entire codon reading down or up and subsequently change the whole protein.
- often results in loss of protein function
Selectable Mutation
- a mutation that has an advantage over a parent
Something easy to isolate. Phenotypic level- you can see it
Non Selectable Mutation
- mutation that doesn’t have an advantage
- DNA level- can’t see mutation easily