The genetic code Flashcards
What does an amino acid look like?
. R
I
H2+N–C—COO-
I
H
What is a peptide bond?
A peptide bond is formed from a condensation reaction between the carboxyl group of one amino acid and the amino group of the adjacent amino acid.
What does a peptide bond look like?
What is the difference in genetic code from protein to RNA?
RNA consists of four nucleotides - A U G C
Protein consists of 20 amino acids, each made from 3 nucleotides.
What is the genetic code?
A triplet code in which three nucleotides in RNA specify one amino acid in protein.
What is a triplet?
Each triplet of nucleotides (A,U,G,C) is a codon.
What is the start codon?
AUG = (Met)hionine
What are the stop codons?
UAA
UAG
UGA
How are the amino acids grouped?
How do mutations affect amino acids?
Mutations can affect biochemical property and therefore function.
It can lead to loss of the function of a protein in a mechanism that may be essential and has no back up.
What are hydrophobic amino acids?
Repels water
Val, Leu, Ile, Met, Pro
What are nucleophilic amino acids?
Donates electron pairs to form chemical bonds
Ser, Thr, Cys
What are basic amino acids?
The R group at pH 7 is basic.
It contains N2.
Binds protons, positive, and nucleophilic.
His, Lys, Arg
What are acidic amino acids?
R group at pH 7 is acidic
Contains carboxylic acid, loses protons, negative.
Asp, Glu
What are aromatic amino acids?
Cyclic - very important as they absorb at 280
Phe, Tyr, Trp
What are amide amino acids?
The amides are cyclic based on the R group.
Gln, Asn
What are small amino acids?
Small in size - Gly, Ala
What are essential amino acids?
Need to be provided through diet.
Thr
Phe, Trp
Val, Leu, Ile, Met
His, Lys
What are non-essential amino acids?
Made within the body
Cys, Ser
Tyr
Gly, Ala
Gln, Asn
Arg
Asp, Glu
What is the structure of Glutamic acid?
CH2 CH2 COOH
What is the structure of Glycine?
H
What is the structure of Lysine?
(CH2)4 NH2
What is the structure of Glutamine?
CH2 CH2 C=O NH2
What is the structure of Methionine?
CH2 CH2 S CH3
What is the structure of Phenylalanine?
CH2 - aromatic ring
What is the structure of Serine?
CH2 OH
What is the structure of Tyrosine?
CH2 - phenol ring
What is the structure of Valine?
CH (CH3)2
What are reading frames?
Once a gene has been sequenced we need to identify the Open Reading Frame.
Every region of DNA has 6 possible reading frames - 3 in each direction.
What is an Open Reading Frame?
ORF is a run of codons that starts with ATG and ends with a termination codon - TGA, TAA or TAG.
It is the frame that produces the longest polypeptide.
What does an ORF look like?
How should you write an open reading frame?
N-Met
amino acid -C
What is the triplet code feature of the genetic code?
Each triplet on the DNA codes for a specific amino acid in the RNA when it is translated.
What is the degenerate feature of the genetic code?
Most amino acids are coded for by more than one codon.
What is partial degeneracy?
The 1st two bases in the codon are the same and the 3rd is one of 3 bases.
What is complete degeneracy?
The 1st two bases in the codon are the same and the 3rd is any of the 4 bases.
What is the non-overlapping feature of the genetic code?
Adjacent codons do not overlap so no single base can take part in the formation of more than one codon.
What is the non-ambiguity feature of the genetic code?
While the same amino acid can be coded by more than one codon (degenerate), the same codon shall not code for two or more different amino acids.
What is the universal feature of the genetic code?
The same sequence of 3 bases encode the same amino acids in all life forms.
What is the polarity feature of the genetic code?
Reads in a 5’-3’ direction
