8.1 - Genes And The Genetic Code Flashcards
What is a gene?
A gene is a particular section of DNA that contains the coded information to make polypeptides and functional RNA such as tRNA and mRNA
What is the locus?
A locus is a specific point on a DNA molecule where a gene is located
How many bases code forone amino acid?
Three bases code for 1 amino acid
Two bases = 16 amino acid possibilities
Three bases = 64 amino acid possibilities
How many different amino acids are there?
There are 20 different amino acids altogether.
What is the name given to 3 bases?
Three bases are often referred to as triplets or codons.
What is the Degenerative code?
As there are 64 possible triplets and only 20 amino acids, it follows that some amino acids are coded for by more than one triplet. This is known as a degenerative code.
What is meant by a non-overlapping code?
Each base is only read once rather than as triplets therefore the same base cannot be in the next triplet/codon
Why is the genetic code referred to as universal?
With a few minor exceptions each triplet code is for the same amino acid in all organisms
What is the ‘start’ amino acid and what bases code for it?
Methionine
AUG
Give the three stop triplets
UAG
UAA
UGA
Describe how a change in one base along DNA molecule may result in an enzyme becoming non-functional
I different base might code for a different amino acid. The sequence of amino acids in the polypeptide produced will be different. This change to the primary structure of the protein might result in a different shaped tertiary structure. The enzyme shape will be different and may not fit the substrate the enzyme substrate complex cannot be formed and so the enzyme is non-functional
