The Genetic Code And Mutations Flashcards
3 features of the genetic code
Non overlapping
Degenerate
Universal
The genetic code
The sequence of base triplets (codons) in DNA which code for specific amino acids
Non overlapping
Each codon is read in sequence separate from the codon before and after it: aka, no nitrogenous base is shared between multiple codons
So each codon has its own 3 bases
Degenerate
Some amino acids are encoded for by more than one triplet and thus codon
Why is the genetic code degenerate?
There are 20 amino acids but 64 possible codons (eg combos of A U C G)
So for every amino acid, there is more than 1 codon which can encode for it
Universal
In all organisms, the same specific base triplets encode for same amino acids
How is the fact that the genetic code is universal provide evidence for evolution?
Because it shows how in all organisms, the code has been preserved from a common ancestor (eg LUCA)
What is a mutation?
When there is a change in the base sequence of DNA in terms of base
When do mutations usually occur?
During DNA replications due to to a copying error
2 types of mutation
Substitution
Deletion
Substitution
When one base is substituted for another
Does substitution mutation mean the protein synthesised will be faulty?
Not necessarily because the substituted base which leads to a different codon could still encode for same amino acid (genetic code is degenerate) possibility it changes still exists though
And has no effect on rest of amino acids encoded for
Deletion
One base is completely removed from the DNA sequence
Does a deletion mutation mean the protein synthesised will be different?
Yes:
Chromosome mutations
When errors in meiosis mean gamete(s) produced contain extra copies of certain chromosomes and the other gamete containing none of these chromosomes
