Can you help me with this genetics questions?

Question

What determines the specifity of DNA?

What are some of the effects when the base in the genetic code is altered?

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Answer 1

Specifity is from the exact sequence of the nucleotides.  For example, altering a single nucleotide in a gene can code for a different protein product, making each allele specific to the individuals.

You can alter bases in different ways.

1. Substitutions - if you simply swap one nucleotide for another (like a T for a C).  This can have a range of effects.  In some instances it has no effect (same-sense mutation) because the new codon still codes for the same amino acid.  In some situations it might mean a different amino acid is coded for (mis-sense mutation).  In some instances, you might create an early stop codon, which will greatly shorten the protein, likely making it non-functional (non-sense mutation).

2.  Additions/Deletions - these mutations occur when you add or remove nucleotides and often have larger effects.  If you add/remove not in multiples of three, then it causes a frameshift where the entire sequence is shifted and all of the amino acids following the mutation will be misread.  If nucleotides are added/removed in a multiple of three, then the effect may be less dramatic because you won't likely cause a complete frameshift.