Nucleic Acid & Amino Acid Sequence Comparison Flashcards
A triplet is a
sequence of three DNA bases that codes for a specific amino acid
A codon is a
sequence of three mRNA bases that codes for a specific amino acid
a codon is transcribed from
the triplet and is complementary to it
An anticodon is a
sequence of three tRNA bases that are complementary to a codon
When comparing the genetic code to amino acid sequences, mRNA codons are often used
The four bases found in RNA molecules (adenine, uracil, cytosine and guanine) have the ability to form
64 codons
The genetic code is degenerate
Multiple mRNA codons can encode the same amino acid
which means that a change in the genetic code doesn’t necessarily result in a
amino acid sequence
Some send important signals to the translation machinery
The START codon marks
STOP codons cause
the start of the protein and therefore initiates the process of translation from the right location (this is always the amino acid methionine in eukaryotic cells, coded for by the codon AUG)
translation to terminate at the end of the protein and do not code for any amino acids
The genetic code is non-overlapping
Each base is
only read once in the codon it is part of
The number of amino acids in a protein can be calculated using the number of coding nucleotides in the mRNA molecule and vice versa:
When given the number of coding mRNA nucleotides, divide by 3 and minus one (for the stop codon – it is best to state this in your answer too)
When given the number of amino acids, multiply by 3 and add 3 (for the stop codon)
In the exam, you may be asked to predict the effect of specific mutations in the genetic code. Remember that the genetic code is degenerate and non-overlapping! Also if stop and start codons are inserted into a coding sequence they can have major effects.You will not be required to memorise specific codons and the amino acids for which they code.
