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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?