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Mutations
http://www.chemistryexplained.com/images/chfa_03_img0589.jpg
• Mutation= A change in an organism’s DNA.
• Types of mutations:
– Point mutation substitutes one nucleotide for
another.
mutated
base
• Point mutation example:
– Sickle Cell Anemia
5
a.
6
7
5
…. CCU G A A GAA …
….. pro glu
glu ….
-globin
7
…. CCU G U A GAA …
…. pro val
glu ….
Hb A
b.
6
Hb S
c.
Fig. 5.1 (a) Point mutation in codon number six of the beta -globin gene results in the
substitution of the amino acid number glutamine with valine and the formation of
haemoglobin S (HbS); (b) Red blood cells in a smear of normal blood containing HbA; (c)
crenated and sickle-shaped red blood cells in sickle cell anaemia.
http://staff.um.edu.mt/acus1/5Mutations.htm
http://www.nhlbi.nih.gov/health/dci/images/sickle_cell_01.jpg
– Frameshift mutation inserts or deletes a
nucleotide in the DNA sequence.
Example:
The Cat Ate The Rat (Remove “e” on 1st “The”)
 = Thc Ata Tet Her At
• Frameshift mutation example:
– Cystic fibrosis
https://health.google.com/health/ref/Cystic+fibrosis
• Mutations can be caused by several factors:
– Replication errors
– Mitosis and meiosis errors
– Mutagens (such as UV ray and chemicals)
– Some cancer drugs
 Mutations in body cells do not affect offspring.
 Some gene mutations do not affect phenotype
(A mutation may be silent)
 Mutations in sex cells can be harmful or
beneficial to offspring.