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MUTATIONS
Mutant
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An organism expressing a mutated gene
Types of mutations
Point mutations (gene mutations) change
in a single DNA base pair.
 Frameshift mutation single base added
and deleted from DNA
 Chromosomal mutations changes in
chromosomes. Insertion, deletion,
inversion and translocation.
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Mutation
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A sudden genetic change
Gene mutations
Point mutations
Most common
 Most mutations are recessive and do not
show.
 Some result in abnormalities that show eg
Albino (shows in animals but lethal in
plants
 Some are lethal mutations and result in
death.
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Chromosome mutations
Chromosome mutations
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Usually more drastic because more genes are
involved.
Occur during mitosis and meiosis, chromosomes
break and rejoin incorrectly.
Usually lethal, therefore, not passed on to future
generations.
Common in plants (polyploidism) 3n, 4n, 6n, not
harmful and results in bigger, better fruits.
Nondisjunction


a.
b.
c.
Occurs when homologous chromosomes fail to
separate correctly during meiosis.
Examples:
Trisomy – extra chromosome, Down’s
syndrome extra 21st chromosome
Triploidy – extra set of chromosomes 3n
Monosomy – missing one chromosome,
Turner’s syndrome one missing X
chromosome
Somatic mutations
Mutations in the body cells
 Not passed on to the children because
they only occur in body cells.

Germ mutations
Mutations in the germ cells (reproductive
cells – gametes – eggs and sperm.
 Passed on to the offspring.
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Causes of mutations
Mutagenic agents are called mutagens.
 Mutagens disrupt normal cellular activity.
 Mutagens: radiation
x-rays
UV light
Smog, smoke, industrial
chemicals, air pollutants.
Viruses
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