Protein Synthesis Flashcards
Gene
length of DNA containing a sequence of bases that code for a specific protein
Sequence of nucleotides
code for the order of amino acids in the protein
determing the folding of the poly peptide chain
sequence of bases
responsible for proteins role
Where are the genes found?
specific locus on the chromosomes
Triplet Code
3 DNA bases in order code for one amino acid
How many different triplets are there?
64
Degenerate
some amino acids are coded for by more than one triplet
How many amino acids exist?
20
How many strands code for a protein?
Only the 1 template strand
Allelles
different forms of the same gene
mRNA
messenger RNA
mRNA Sugar
Ribose
mRNA Bases
G to C and A to U
Base U
Uracil
mRNA Shape
single stranded
3 bases in mRNA
codon
tRNA
transfer RNA
tRNA Sugar
Ribose
tRNA Bases
G to C and A to U
tRNA Shape
single stranded
clover leaf shape due to base pairing
3 bases in tRNA
anticodon
Transcription
gene in DNA is copied into mRNA
mRNA is small enough to leave the nucleus
attaches to a ribosome
DNA —–> mRNA
DNA helicase unwins double helix breaking hydrogen bonds
free RNA nucleotides bind to exposed complemetary bases
forming hydrogen bonds
RNA polymerase forms phosphodiester bonds between adjacent nucleotides
forming a sugar-phosphate backbone
mRNA strand now detaches from the template/sense strand
the 2 DNA starnds join back together by complementary base pairing
wind back up into a double helix
Intron
interupting sequence
do not code for anything
Exon
coding genetics of the sequence
Post-Transcriptional Modification
RNA polymerase makes a complementary copy of a run of continuous bases
introns are removed by enzymes bfore the mRNA levaes the nucleus
just leaving exons
Many exons
can be arranged in multiple ways to make different polypeptides
Translation
conversion of mRNA sequence into amino acids
ribosome attaches to the start codon
tRNA with complementary anti codon attaches to the start codon
bringing its specific amino acid
this also happens for the second codon
Ribosome + ATP causes the formation of a peptide bond between the 2 amino acids
ribsome moves along the mRNA by one codon and the first tRNA molecule is released
goes back to the pool in the cytoplasm to pick up another amino acid
this continues down the mRNA until reaching a stop codon
many ribosomes can attach to create many polypeptides
Translation reults in
the polypeptide chain is then folded into the secondary, tertiary and quaternary proteins
Overview of Protein Synthesis
DNA
-Transcription
Pre-mRNA
-Splicing
Mature -mRNA
-Translation
Polypeptide Chain
-Folding
ProteinMutation
change in the base sequence of DNA
What causes mutation?
exposure to UV light
X-Rays
High energy radiation
Carcinogens
Frame Shift
Caused by addition or deletion mutation
by adding or removing a base the gene is read in the wrong 3 base groups
resulting in entirely different polypeptides
Point mutation
Substitutions
only affect one particular point on the polypeptide chain
NonSense Mutation
substitution of a base leads to a premature stop codon
successful synthesis is very unlikely
Stop Codons
UAA
UAG
UGA
MisSense Mutation
change in base leads to a different amino acid
as there is only one amino acid different
you can get away with it sometimes but can also have consequential affects
Silent Mutation
since some amino acids are degenerate substitution can lead to the same amino acid being coded for so there is no change
