Mutations
Any mistake or change in DNA sequence Mutations Any mistake or change in DNA sequence What causes them? Random or Environmental influences – X-rays, UV rays, radioactive materials, chemicals, cigarettes, medications
Chromosomal mutation: affects whole or part of a chromosome Gene mutation: Changes to the bases in the DNA of ONE gene
1. Gene Mutations Change in one or more nucleotides Affects the amino acids and protein produced 2 types
Point Mutation Substitution: Change in a single base pair in DNA Ex: The dog bit the CAT The dog bit the CAR
Sickle Cell Anemia
Some Point Mutations are Harmless What amino acid is represented by the DNA sequence GGA? What amino acid is represented by the DNA sequence GGC? This change in the 3rd base of the codon is a point mutation, yet the amino acid would remain the same. Therefore, the protein would NOT be affected.
Some Point Mutations are Harmless This type of point mutation is called a silent mutation. Silent Mutations are possible due to the redundancy in the genetic code.
Frameshift Mutation Single base pair is added or deleted from DNA Causes a shift in the “reading frame” Ex: Cystic Fibrosis EX: cystic fibrosis
Kinds of Frameshift Mutations Insertion: one or more bases are added into the mRNA strand Deletion: one or more bases are removed from the mRNA strand
Nonsense Mutations A point mutation or a shift in the reading frame can sometimes cause a premature STOP codon This type of mutation is called a nonsense mutation If the nonsense mutation occurs early in the mRNA sequence, the protein is greatly shortened and most likely non functional
Some mutations are beneficial Gain-of-function mutations produce a functional protein that results in an entirely new trait These mutations are usually beneficial and result in an advantage in an organism’s environment EX: The mutation that resulted in eyesight
Practice – Name that Mutation 1 2 Deletion ~ Frameshift Silent ~ Point 4 3 Insertion, nonsense ~ Frameshift Point 6 5 Deletion ~ Frameshift Nonsense ~ Point