A permanent change in a cell’s DNA.

MUTATION

• Cells have checkpoints to repair damage missed earlier in DNA replication.

• Sometimes the cell doesn’t repair the damage.

• If the damage goes unrepaired it can result in mutation.

•Radiation (X rays) •UV light •Mutagens

• A mutagen is a substance, such as a chemical, that causes mutations

CAUSES OF MUTATIONS

MAIN CATEGORIES OF MUTATIONS• Substitution: Involves a chemical change in one base

pair. • Missense• Nonsense

• Frameshift: The addition or loss of a nucleotide that results in a change of the “frame” of the amino acid sequence• Insertion• Deletion

• Duplication: The copying of a nucleotide or amino acid sequence

A single base is changed to cause substitution of an amino acid.

DNA = TAC GAG AGC CCA ATT

RNA = AUG CUC UCG GGU UAA

A.A. = Start leucine serine glycine stop

DNA = TAC GAG CGC CCA ATT

RNA = AUG CUC GCG GGU UAA

A.A. = Start leucine alanine glycine stop

MISSENSE MUTATION

• Characterized by the improper development of the cartilage in legs and bones resulting in dwarfism

ACHONDROPLASIA

A point mutation that results in a premature stop codon.

DNA = TAC GAG AGC CCA ATT

RNA = AUG CUC UCG GGU UAA

A.A. = Start leucine serine glycine stop

DNA = TAC GAG ATC CCA ATT

RNA = AUG CUC UAG GGU UAA

A.A. = Start leucine stop

NONSENSE MUTATION

Characterized by the progressive weakening of many muscles in the body

MUSCULAR DYSTROPHY

A mutation in which bases are added to the DNA sequence

DNA = TAC GAG AGC CCA ATT

RNA = AUG CUC UCG GGU UAA

A.A. = Start leucine serine glycine stop

DNA = TAC TGA GAG CCC AAT

RNA = AUG ACU CUC GGG UUA

A.A. = Start threonine leucine glycine leucine

INSERTION MUTATIONS

Characterized by chronic inflammation of the intestinal tract causing diarrhea, abdominal pain, nausea, fever

CROHNS DISEASE

A mutation in which part of the DNA is missing.

DNA = TAC GAG AGC CCA ATT

RNA = AUG CUC UCG GGU UAA

A.A. = Start leucine serine glycine stop

DNA = TAC AGA GCC CAA TTT

RNA = AUG UCU CGG GUU AAA

A.A. = Start serine arginine valine lysine

DELETION MUTATIONS

• Characterized by a high pitched cry, similar to a cat, during infancy

• Symptoms are lowered intellectual disability, delayed development, small head and weak muscle tone

CRI DU CHAT

A type of mutation in which a portion of a genetic material or a chromosome is duplicated or replicated, resulting in multiple copies of that region.

DNA = TAC GAG AGC ATT

RNA = AUG CUC UCG UAA

A.A. = Start leucine serine stop

DNA = TAC GAG GAG AGC ATT

RNA = AUG CUC CUC UCG UAA

A.A. = Start leucine leucine serine stop

DUPLICATION

Characterized by damage to nerves leading to atrophy of muscles in hands and lower legs

CHARCOT-MARIE TOOTH DISEASE

• The movement of a gene fragment from one chromosomal location to another, which can alter or abolish expression

GENE TRANSLOCATION

• Mutation is passed on to offspring and will be present in every cell of the offspring

• Alters mutated cell and future daughter cells

• May cause no result in a cell if the particular sequence is not needed.

• Cell death may occur

• May lead to cancer

SOMATIC VS. GERM CELL MUTATION

Somatic Germ

• It’s estimated that mutations occur at the rate of 1 in every 50 million nucleotides.

• This means that each new cell contains some 120 new mutations. Should we be worried?

• NO – As much as 97% of our DNA does not encode anything. “junk DNA”

• Can mutations be beneficial to us?

• Evolution – The changes seen in the inherited traits of a population from one generation to the next.

MUTATION…GOOD?