Download lab 10 SCA HO

What is anemia?
Red blood cells are ‘bags’ of
hemoglobin, an oxygen-carrying protein
What is hemoglobin?
What is sickle cell anemia?
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Hemoglobin is a protein in
red blood cells
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Carries oxygen
It binds oxygen in the lungs,
carries the oxygen throughout
the body, and release it to the
body’s cells and tissues.
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The heme group is the site
of oxygen (O2 ) binding
The Hb molecule has a
globular shape
Sickle cell anemia
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The normal RBC is flexible and gets
through the smallest blood vessels.
The sickle cells are rigid and sticky;
they block the vessels and restrict the
normal flow of blood and oxygen to
organs.
The sickle cells are more
fragile–they’re destroyed rapidly,
leading to anemia.
An inherited blood disorder
that is caused by a mutation
in the gene that codes for
the protein hemoglobin
This mutation changes the
hemoglobin protein to
become ‘sticky’
Hemoglobin molecules stick
together and form long
fibers that distort the shape
of the red blood cells into
sickles
Hemoglobin S –
a mutant form of Hb
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HbS is found in people with
sickle cell disease.
Only 1 amino acid in the ß
subunit is changed
About 8% of African Americans
carry the HbS mutation in one of
the two ß subunits
People with sickle cell anemia
carry the HbS mutation in both
of the ß subunits
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0.15% of African Americans
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How do genes code for
proteins?
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The genetic code–the
rules for translating the
order of bases in DNA
into the order of amino
acids in a protein
Codon: 3 bases that code
for an amino acid
A one nucleotide change
in the gene for the
hemoglobin β chain
changes amino acid #6
Two ß subunits: HbA and HbS
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HbS
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A change in a single amino acid
A change in the shape of the cell and causes
DISEASE
Inheriting Sickle Cell Anemia
– a genetic disease
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Only 20%-40% of the ß subunit is HbS
They produce HbS and no normal HbA, and suffer
from sickle cell anemia.
The HbS gene is recessive.
This means that a person
must have two copies of the
mutant gene, one from each
parent, to have sickle cell
disease.
If a person inherits one
normal gene (HbA) and one
abnormal gene (HbS), the
person is a carrier.
The abnormal gene can be
passed on to offspring, but it
does not cause the disease.
Sickle cell trait and malaria
This is called sickle cell trait, and can be passed
on to a person’s children.
If a person has two copies of the mutated
gene?
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A change in a single nucleotide in the gene for the
β subunit of hemoglobin (CTC to CAC)
They produce enough normal hemoglobin (HbA)
that they do not experience health problems.
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And causes a disease – sickle
cell anemia
What happens if a person has one normal
gene and one mutated copy?
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Mutant (HbS)
the shape of the hemoglobin
molecule
the shape of the RBC
makes the cells more fragile
Sickle cell trait
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Normal (HbA)
There is only 1 amino acid
difference between HbA and
HbS, but it causes the Hb
molecules to stick together
when oxygen levels are low
This changes
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HbA
A small change makes a BIG
difference
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People (and particularly
children) infected with the
malaria parasite are more
likely to survive the acute
illness if they have sickle cell
trait.
The sickling of the cells
interferes with the growth of
the parasite
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