Gene MutationsLS: Molecular

Gene Mutations✦ A mutation is a permanent change in

the DNA sequence that affects genetic information.

✦ Most gene mutations involve a change in a single nucleotide, a point mutation.

✦ A change in a single base changes the amino acid, which changes the structure of the protein.

Mutations

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Spontaneous Mutations✦ Single Nucleotide

Polymorphisms (SNPs) make up the genetic differences among individuals.

✦ SNPs are most common in non-coding regions of DNA.

Missense Mutations✦ Missense mutations exchange one amino acid

for another.

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Nonsense Mutations✦ A nonsense mutation is a single base mutation

that codes for a stop factor prematurely. THE FAT.

Synonymous Mutations A synonymous mutation or silent mutation

happens when changes in the DNA sequence do not result in changes in the protein produced.

EXAMPLE:A change from CCU to CCC results in no change in the protein because both codons code for the same amino acid (Proline).

✦ A protein’s shape is determined by the order of amino acids in the protein.

✦ The order of the amino acids in a protein is determined by instructions coded in the DNA.

Protein Synthesis

Frameshift Mutations✦ Frameshift mutations cause a shift in

each three-base segment following the point where the mutation occurred.

➡ Insertion is when an extra base is inserted into a section of mRNA.

➡ Deletion is when one of the bases are lost from a section of mRNA.

Frameshift Mutations: Deletion

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Deletion

Every amino acid (word) is changed from the point of deletion and on. Thus the entire protein (sentence) is changed

Frameshift Mutations: Deletion

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Insertion

Every amino acid (word) is changed from the point of insertion and on. Thus the entire protein (sentence) is changed

Mutagens✦ A mutagen is a physical or chemical agent that

changes the genetic information of an organism increasing the frequency of mutations.

➡ Chemicals ➡ Free Radicals ➡ Radiation ➡ Smoking ➡ UV Light ➡ Viruses

Chemical Mutagenesis✦ Chemical Mutagenesis is

when chemical compounds alter the chemical structure of the nucleotides.

Radiationn Radiation modifies bases by breaking the

sugar-phosphate backbone of DNA.

Viral Transformation✦ Transformation occurs when viral DNA is

inserted into one of the host cell’s chromosomes.

✦ Insertion of viral DNA may disrupt a normal gene.

HPV

Original Gene

Disrupted Gene