The Genetic Code Flashcards
What is the genetic code?
the sequence of base triplets (codons) in mRNA which codes for a specific amino acid in protiens
What is a start codon?
start of every gene
What is a stop codon?
end of every gene - 3 bases that don’t code for an amino acid and mark the end of a polypeptide chain and causes ribosomes to detach which stops translation
What are the features of the genetic code?
- degenerate
- universal
- non overlapping
What does it mean that the genetic code is degenerate?
- most amino acids have more than one codon
- there are more possible triplets (64) than amino acids (20) so some amino acids are coded for by mire than one triplet
Why is it good that the triplet code is degenerate?
if a mutation occurs, even though the triplet of bases will be different, it may still code for the same amino acid so have no effect
What does it mean that the genetic code is universal?
- same codon (triplet of bases) codes for same amino acid in all organisms (few minor exceptions)
Why is it good that the genetic code is universal?
genetic engineering is possible
What does it mean that the genetic code is non-overlapping?
each nucleotide is read only once - base triplets don’t share their bases
- each base in a gene is only part of one triplet of bases that codes for one amino acid therefore each codon is read as a discrete unit
Why is it good that the genetic code is non-overlapping?
if a mutation occurs it will only affect one codon which means it will only efect one amino acid
What are introns?
sections of DNA that don’t code for amino acids
What are exons?
sections of DNA that do code code for amino acids
How can DNA sequences be found out from mRNA codons?
mRNA is a complementary copy of the DNA template so DNA sequences is made up of baes that would pair with mRNA e.g. mRNA = UCU, DNA=AGA
How can tRNA anticodons be found out from mRNA codons?
tRNA anticodons are complementary copies to mRNA codons e.g. mRNA = UCU, tRNA = AGA
