start up march 6, 2008
DESCRIPTION
Start Up March 6, 2008. Get out A-13: SA p. 322 Refer to Notes and answer the following question in your Start up. Describe and give examples of the 4 Patterns of Inheritance that you have learned. Complete dominance/recessiveness Incomplete dominance Co-dominance Sex-linked. - PowerPoint PPT PresentationTRANSCRIPT
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• Mendel’s laws of heredity also can be applied to traits that have more than two alleles.
Multiple Alleles Govern Blood Type
• The ABO blood group is a classic example of a single gene that has multiple alleles in humans.
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Alleles for ABO
Type Symbol
A IA or A Both A & B are
B IB or B dominant to O, but Co-
dominant to each other.
O i or O Recessive to both A & B
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Multiple Alleles Govern Blood Type
Human Blood Types
lA lA or lAlilB lB or lBilA lB
ii
Genotypes Surface Molecules Phenotypes
AB
A and BNone
ABABO
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• The gene for blood type, gene l, codes for a molecule that attaches to a membrane protein found on the surface of red blood cells.
The ABO Blood Group
• The lA and lB alleles each code for a different molecule.
• Your immune system recognizes the red blood cells as belonging to you. If cells with a different surface molecule enter your body, your immune system will attack them.
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• The lA allele is dominant to i, so inheriting either the lAi alleles or the lA lA alleles from both parents will give you type A blood.
Phenotype A: Blood type A
• Surface molecule A is produced.
Surface molecule A
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• The lB allele is also dominant to i.
Phenotype B: Blood type B
• To have type B blood, you must inherit the lB allele from one parent and either another lB allele or the i allele from the other.
• Surface molecule B is produced.
Surface molecule B
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• The lA and lB alleles are codominant.
Phenotype AB: Blood type AB
• This means that if you inherit the lA allele from one parent and the lB allele from the other, your red blood cells will produce both surface molecules and you will have type AB blood.
Surface molecule B
Surface molecule A
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• The i allele is recessive and produces no surface molecules.
Phenotype O: Blood type O
• Therefore, if you are homozygous ii, your blood cells have no surface molecules and you have blood type O.
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• Determining blood type is necessary before a person can receive a blood transfusion because the red blood cells of incompatible blood types could clump together, causing death.
The importance of blood typing
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Blood type A
Blood cells have
surface protein A
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Blood type B
Blood cells have
surface protein B
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Blood type AB
Blood cells have
surface proteins
A and B
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Blood type O
Blood cells have
no surface
proteins