lecture 18 november

Today is 18 November , we have lecture on the mutation. Mutation is a sudden random change in genetic material of a cell that potentially can cause differ in appearance or behavior from abnormal type. We have two type of mutation which are base substitution and frameshift . in base substitution we have silent, missense, and nonsense. In frameshift mutation we have insertion or deletion and shift in reading frame.

Silent mutation is an alteration in a DNA sequence that does not result in an amino acid change in a polypeptide.

Missense mutation is a change in the first or second base and lead to significant changes in protein.

Nonsense mutation is change from codon for an amino acids to stop codon.

Frameshift mutation is a type of gene mutation where in the addition or deletion of nucleotide causes a shift in the reading frame of the codons in the mRNA.in base insertion, the addition of one or a few bases to triplet sequence in DNA. Base deletion is loss of one or a few bases that can cause frameshift mutation.

Mutagen is an agent that cause an increase in number of mutants in the population. There are four type of mutagens which are base analogues, chemical mutagen, radiation and intercalating agents.

Base analogues substituted a standard base during replication which appear in daughter cells in a later geeration.

Chemical mutagens is a substance that can alter a base that is already incorporated in DNA and change its hydrogen bonding specificity

Radiation have two type which are ionizing and nonionizing. Ionizing is more powerful form short wavelength rays while nonionizing is UV radiation at 260 nm is the most effective as a lethal agent.

Intercalating agents is planar with 3 ringed molecules whose dimensions are equivalent to purine

There are two kind of identifying mutants which is nonselectable and selectable. Positive selection is deselection is done by rejecting unwanted parents while negative selection is selection cells that are unable to carry out certain function and it use replica technique.

    Lasty, we learn on Ames test to identify carcinogens . many mutagen are carcinogens . assume that a mutant can revert to wild type in the presence of a mutagen.