Mutation

[amish1]

A mutation that deletes one or two DNA nucleotides changes gene function more drastically than a substitution of one nucleotide for another. Why?

[Robb Phoenix]

A Knife which deletes one or both of your hands changes your functions more drastically than a substitution of one hand with another.Why?

[amish1]

It unables us to be able to function to our full potential. But with at least one hand we can still do some things and can teach ourselves to adapt to just one hand or an attachment as well. Without either we're almost helpless.

[Robb Phoenix]

Ya got it!
;-)

[gen2]

The answer is not quite so anthropomorphic as Robb suggests. Each nucleotide does not work in isolation when coding for an amino acid, they are read in groups of threes called codons. A substitution of one nucleotide for another will just change a single amino acid in a long protein chain and may not fall in a critical region of that protein and so may not impair its function.

If a single nucleotide is removed, then then all subsequent codons (groups of three) will be read out of sequence and the whole remaning length of the protein will have totally different amino acids and so its original function will be totally destroyed.

eg. Consider this list of 3-letter words:

CAT / DOG / RAT / PIG / RAM / EWE / BAT

[gen2]

now what if the first D is substituted with an H? We get:

CAT / HOG / RAT / PIG / RAM / EWE / BAT

But if that D is deleted altogether: We get

CAT / OGR / ATP / IGR / AME / WEB / AT?