Mutations

What are mutations?

-They are mistakes made in our genetic code, which may or maynot result in the wrong protein being made.

Mutagens:Are any chemical or radiation that causes a change in our genetic code.

Examples:

X-rays, UV sunrays, asbestos and coal dust.

Carcinogens:-Are mutagens that cause a mistake in the genetic code that leads to uncontrollable cell division.- This results in CANCER.

-Examples include: Mercury, UV rays and cigarettes

Two categories of mutations:Germ mutation:

-mutations which occur in the sperm or the egg. If fertilized this mistake would be passed on to the child.

Example: Sickle cell anemia

Somatic mutations:-mutations which occur in a body cell. These cells are not passed on to the offspring.

-Example: Skin cancer

Types of mutations (either germ or somatic):

1. Chromosomal mutations:-entire chromosomes is affected

therefore many genes are involved resulting in the most severe forms of mutations.

-Example: Down SyndromeEdwards Syndrome

Trisomy 21~Down Syndrome

Trisomy 18~ Edwards Syndrome

-One single change in a DNA nucleotide is made therefore only affecting one single gene.

2. Gene mutation:

Example:Albinism:

Types of gene mutations:

1. Silent or Neutral Mutation-a change in one base does

not alter the amino acid sequence.

2. Missense Mutation:-one DNA nucleotide is changed

causing it to code for a different amino acid. This mistake still codes for an amino acid BUT just the wrong amino acid.

3. Nonsense Mutations:-one DNA nucleotide is changed

forming a stop codon in the middle of a gene resulting in a shortened amino acid sequence that codes for NO protein.

4. Frameshift mutation:-one or two nucleotides gets

added to a gene resulting in the entire sequence to get shifted down and throwing off the entire amino acid sequence.