different types of mutations

NONSENSE MUTATIONS: a nonsense mutation, the new nucleotide changes a codon that specified an amino acid to one of the stop codons (TAA, TAG, or TGA). Therefore, translation of the messenger RNA transcribed from this mutant gene will stop prematurely. The earlier in the gene that this occurs, the more truncated the protein product and the more likely that it will be unable to function.

INSERTION: occur when extra DNA is added into an existing gene


FRAMESHIFT:

mutations result from either addition or deletion of one or two nucleotide bases. When this occurs the reading frame is changed so that all the codons read after the mutation are incorrect, even though the bases themselves may be still present.

POINT MUTATIONS: are small changes often in a single nucleotide base.

TRANSLOCATIONS: are the transfer of a piece of one chromosome to a nonhomolougus chromosomes. Translocations are often reciprocal; that is, the two nonhomologues swap 

• the break may occur within a gene destroying its function
• translocated genes may come under the influence of different promoters and enhancers so that their expression is altered. 
• the breakpoint may occur within a gene creating a hybrid gene. This may be transcribed and translated into a protein with an N-terminal of one normal cell protein coupled to the C-terminal of another. The Philadelphia chromosome found so often in the leukemic cells of patients with  (CML) is the result of a translocation which produces a compound gene (bcr-abl).

SENSE MUTATIONS:A mutation that changes a termination  codon into one that codes for an amino acid. Such a mutation results in an elongated protein. 

DELETION MUTATIONS: result in missing DNA are called deletions. These can be small, such as the removal of just one "word," or longer deletions that affect a large number of genes on the chromosome. Deletions can also cause frameshift mutations. In this example, the deletion eliminated the word cat.