Download 11a - Genetic Mutation Notes

Genetic Mutations
Mutation:
An unpredictable change in the genetic
material of an organism
Gene Mutation:
A change in the structure of a DNA
molecule, producing a different allele of a
gene
Chromosome Mutation:
A change in the entire structure or number
of whole chromosomes
Causes of Mutations
Mutations occur randomly with no obvious cause.
Mutagens: Substances that increase the chances
of mutation occurring
Ex: Ionizing Radiation, Ultraviolet Radiation,
Smoking, UV light
Types of Mutations
• Base Substitution – One nucleotide base
takes the place of another
• One amino acid is changed in the sequence
Types of Mutations
• Base Addition – One or more extra
nucleotide bases added to a sequence
• Base Deletion – One or more nucleotide
bases are lost from the sequence
• Incorrect sequence of amino acids
• Incorrect sequence of amino acids
• Frame Shift Mutations
Which types of mutations have the
greatest impacts?
Silent mutations – Mutation that has no
apparent effect on an organism
Sickle Cell Anemia
Sickle Cell Anemia
• Base substitution with a significant side effect on
phenotype
• The affected gene codes for the oxygen carrying
pigment HAEMOGLOBIN.
Normal Amino Acid Sequence:
Val-His-Leu-Thr-Pro-Glu-Glu-LysSickle Cell Anemia Sequence:
Val-His-Leu-Thr-Pro-Val-Glu-Lys-
• When haemoglobin is not combined with
oxygen, the β chains are less soluble causing
them to stick to each other.
• This pulls RBC’s out of shape into a sickle
shape.
Phenylketonuria (PKU)
• Base substitution
• The affected gene codes for an enzyme
(phenylalanine hydroxylase), which is not
present in people with the mutation
• This enzyme helps catalyse the
conversion of phenylalanine to triosine,
which is then converted to melanine
Effects of PKU
• Lighter skin colour
• Accumulation of
phenylalanine in blood and
tissue fluid, causing severe
brain damage
• Babies are tested for PKU
at birth for prevention