Achange in the natural sequence of bases in dna structure is called a

A change in the natural sequence of bases in DNA structure is called a mutation.

1. Point mutation - This mutation result in the change of single nucleotide in the given DNA sequence. For e.g in a sequence AGGAATC if G changes to C the new sequence would be ACGAATC and this is called a point mutation.

2. Frameshift mutation-This mutation refers to the alteration of the open reading frame of a sequence due to insertion or deletion of several nucleotides in a sequence for e.g if you have a sequence AAATTGG and there is a deletion of AATT  you get AGG. This is an example of a frameshift mutation.

one characteristic that is shared by all is a soft body. many

of these invertebrate animals also have an outer shell to protect their

body. oysters, clams, snails, and mussels are all mollusks. so are octopuses, squids, and slugs. mollusks live on land and in freshwater.