DNAGENE MUTATIONS DNAGene Mutations Protein synthesis does encounter

DNA/GENE MUTATIONS

DNA/Gene Mutations �Protein synthesis does encounter errors �Errors in final sequence of amino acids can be traced to errors in the original strand of DNA �Can effect the primary protein structure and ultimately the final shape and function of the protein �Two types: point mutations and frameshift mutations

Lets see what happens! �Look at A and locate the substitution �Transcribe that part of the gene into the codon it will code for. �What amino acid should be there normally? What amino acid is there now?

Point Mutations Involve the substitution of one nucleotide for another �Three types of substitution: 1. Silent mutation 2. Nonsense mutation 3. Missense mutation � Effects vary from going unnoticed to completely changing shape of final protein

Silent Mutation � NORMAL STRAND OF DNA: TAC TTC GAC GTG ACT • SUBSTITUTED BASE PAIR: TAC TTT GAC GTG ACT DNA ◦ ◦ Amino Acid AAG = lysine In normal strand: TTC DNA ◦ m. RNA Amino Acid AAA = lysine In substituted strand: TTT Same amino acid, so there is no change in protein structure

Nonsense Mutation � NORMAL STRAND OF DNA: TAC TTC GAC GTG ACT � SUBSTITUTED BASE PAIR: TAC ATC GAC GTG ACT DNA m. RNA Amino Acid • In normal strand: TTC AAG = lysine DNA � In m. RNA Amino Acid substituted strand: ATC UAG = stop � Substituted base codes for a stop codon which can have disasterous effects because the protein isn’t finished

Missense Mutation � NORMAL STRAND OF DNA: TAC TTC GAC GTG ACT • SUBSTITUTED BASE PAIR: TAC TCC GAC GTG ACT DNA ◦ m. RNA Amino Acid AAG = lysine In normal strand: TTC DNA m. RNA Amino Acid ◦ AGG = arginine In substituted strand: TCC ◦ Different amino acid, so there is a change in protein structure

Frameshift Mutations Caused by either the addition or removal of one or more nucleotides in the original strand of DNA �Two types: 1. Insertion 2. Deletion � Called frameshift because the addition or removal shifts the “frame” that is read for the amino acid codes

Insertion � NORMAL STRAND OF DNA: TAC TTC GAC GTG ACT C � INSERTION: TAC � By TT C C G A C G T G A C T inserting one base, the entire DNA strand is read differently and can result in a different final protein shape & function

Deletion � NORMAL STRAND OF DNA: TAC TTC GAC GTG ACT C � DELETION: T A C T T C G AG TG A C T � By deleting one base, the entire DNA strand is read differently and can result in a different final protein shape & function