Topic 2B The genetic code

What makes a genetic code ?

3 neucleotides ( their 3 bases, a triplet code, a codon )

Definition of a gene ?

A sequence of bases on a DNA molecule which codes for a sequence on a polypeptide chain.

what is mRNA ?

Messenger RNA is a complimentary strand to the original DNA sequence.

What are non-coding DNA sequences used for ?

These are DNA sequences that are involved in effectively regulating the protein coding sequences, turning genes on or off.

What is a non-overlapping code ?

Three bases are code for one amino acid, for example in UUUAGC, UUU is one amino acid, UUA will not be read as an amino acid, it does not overlap.

What are the drawbacks of overlapping code ?

1.It may be economical, but it is limiting as amino acids that can be coded side by side are limited.

2. Changing one base in an overlapping code leads the 3 other amino acids to also be affected, other amino acids may be affected by one change on one base.

3. If the codon is partly overlapping then two amino acids would be affected.

What is the benefits of a non-overlapping genetic code ?

A mutation on one codon will not affect other amino acids as well.

What is a degenerate code ?

A genetic code has more information than it needs, the amino acid is determined by the first 2 nucleotides.

What are the benefits of a degenerate code ?

A degenerate code prevents a mutation from affecting the amino acid formed.