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Barr Bodies and Blood Types
Barr Bodies
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X-inactivation in female mammals
In females, one of the two X chromosomes in each somatic (body) cell becomes inactive during embryonic development
Why? ◦ Cells of females and males would have same effective dose of genes on the X chromosome
Inactive X chromosomes called Barr bodies
BARR BODY
Found in females
One X chromosome in each cell is randomly inactivated
Inactivated X chromosome seen as a darkly staining area in the nucleus of a cell
How many active chromosomes are found in the cells of a human female?
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Barr Body
Do you see the Barr body?
Barr Bodies in Cats
Calico cat ◦ Generally all females ◦ One of several genes controlling fur color found on X chromosome ◦ Gene on X chromosome codes for either orange or black color ◦ Color pattern determined by random inactivation (Barr body)
Why do you think Calico Cats are usually all female?
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Ex: Tortoiseshell (Calico) cats
animation
Calico Cat Color Inheritance
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Calico Cat
There have been instances of male Calico cats found ◦ How could this happen? ◦ HINT: Male calico cats are sterile
Example in humans Anhidrotic ectodermal dysplasia ◦ X linked mutation prevents the development of sweat glands
◦ A woman who is heterozygous will have patches of normal skin and patches of skin without sweat glands
◦ Difficulty controlling body temperature
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Blood Types
ABO BLOOD TYPES
Example of codominance Blood type depends on the presence or absence of certain carbohydrates (antigens) on surface of red blood cells 3 alleles are possible: ◦ IA :Type A Blood ◦ IB :Type B Blood ◦ i :Type O Blood
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ABO BLOOD TYPES
IA and IB are codominant to each other when they are paired.
i allele is recessive to both IA and IB
If mom is homozygous for type A blood and dad is Homozygous for Type B blood, all of the offspring will have what blood Type?
Which blood type has no antigens? Which blood type has both antigens? Which blood type accepts all the other blood types?
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ABO Blood Types
Why is it important to get the right blood type when getting a transfusion?
◦ Transfusion Reactions Immune system (antibodies) will attack cells that have an antigen that the body doesn’t recognize as “self”
ABO Blood Types
Which square shows type O blood?
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ABO Blood Types Blood typing is actually far more complicated than“A”,“B”, and“O”
ABO are the MAJOR antigens
There are also MINOR antigens ◦ Rh factor: “+” or “-”
Rhesus macaque
ABO Blood Types
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ABO Blood Types
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