11/13/2015 Barr Bodies and Blood Types Barr Bodies 1 11/13/2015 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? 2 11/13/2015 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? 3 11/13/2015 Ex: Tortoiseshell (Calico) cats animation Calico Cat Color Inheritance 4 11/13/2015 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 5 11/13/2015 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 6 11/13/2015 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? 7 11/13/2015 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? 8 11/13/2015 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 9 11/13/2015 ABO Blood Types 10.