Lecture 3 Flashcards
Define amino acid.
the building blocks of polypeptides
How many animo acids are there?
20
Define peptide bond.
between the carboxyl group of one animo acid and amino group the next
What are the three parts of an animo acid?
-carboxyl group
-R-group
-amino group
(usually an additional hydrogen)
Define polypeptide.
a string of amino acids joined by peptide bonds
What is the START codon?
AUG–> Met–> M (read on mRNA 5’–>3’)
What are the STOP codons?
1) UUA
2) UUG
3) UGA
In which direction is an mRNA translated?
from the 5’–> 3’
In which direction is a polypeptide synthesized?
from the amino (N-terminus) to the carboxyl (C-terminus)
Define UTR.
UnTranslated Region; often two on each end that help initiate and terminate translation
What are the 3 phases of translation?
1) Initiation (finds start codon, assembles ribosome complex)
2) Elongation (A–> P–> E)
3) Termination (@ stop codon- blank tRNA, release factors–> disassemble)
Where does translation happen in a bacteria vs a eukaryote?
cytoplasm vs inside nucleus–> coupling of transcription and translation in prokaryotes
Define polycistronic mRNA.
in bacteria, an mRNA that codes for multiple genes
Define synonymous codons.
codons that specify for the same animo acid–> redundancy
Define third-base wobble.
How the third codon is often “flexible” and if changed will still result in the same amino acid
How do aminoacyl-tRNA synthesases “translate” the genetic code?
they provide tRNA with a charge in order to pair the correct amino acids (so the tRNA can read the mRNA aka “google translate”)
What side of the tRNA attaches to an amino acid?
the CCA terminus at the 3’ end
Define point mutation.
a change in one or more DNA base pairs
Define silent mutation.
does not alter the phenotype (protein produced)
Define missense mutation.
a change in a base that may or may not affect the protein (redundancy)
Define nonsense mutation.
usually and early stop–> probably nonfunctional
Define frameshift mutation.
insertion or deletion of a single base pair that changes the reading frame
*a +/- 3x codon can change the protein but it will not change the frame
Define regulatory mutation.
a mutation that occurs in a noncoding region of the mRNA
–>can change #/production of mRNAs
Define forward mutation.
coverts w+ to a mutant
Define reverse mutation.
converts mutant to w+ or near w+
What is the effect of redundancy in the genetic code?
emphasizes variability w/o selective pressure from evolution
