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Pleiotropy
Definition
• The ability of a gene to affect more than
one characteristic.
A
B
C
Several characteristics are affected
by the single gene
Sickle cell disease
• The gene Hb codes for production of
haemoglobin.
• Hbs is a mutation.
• Mutant haemoglobin results in:
– Brain damage
– Heart and blood vessel damage
– Spleen enlargement then atrophy
– Kidney damage leading to blood in urine
PKU (phenylketonuria)
• The PKU gene codes for the enzyme
phenylalanine hydroxylase.
• This enzyme converts the phenylalanine to
tyrosine. Both are amino acids.
• Mutations to the gene result in:
– Mental retardation
– Reduced hair and skin pigmentation
– Damage to body parts from toxic levels of
phenylalanine
• PKU is totally benign if a diet free from
phenylalanine is maintained.
Fruit fly and vestigial wing
• The vestigial gene plays a critical role in
wing development.
• vv will develop short wings
• The affects are:
– Cannot fly
– Number of egg strings in a fly's ovaries
changes
– Position of bristles on a fly's scutellum alters,
– Length of a fly's life decreases
Pigmentation and deafness in cats
• About 40% of cats with white fur and blue
eyes are deaf
• The gene affects pigmentation as well as
ability to hear
• Pigmentation may play a role in
maintaining fluid in ear canals