Human Genetics

1
Human Genetics

• Chapter 11

2
Blood Type

• Some genes have more than two alleles. Blood
  type is one of these.
• A blood type is determined by the presence or
  absence of certain chemicals called antigens in
  the blood.
• Type A blood has the A antigen.

3

• Type B blood has the B antigen.
• Type AB blood has both the A and B antigens.
• Type O blood has neither A not B antigens.
• Another antigen used in blood typing is Rh
  factor.
• Rh is controlled by more than one gene.

4

• A person whose blood type is Rh positive has at
  least one of the positive alleles.
• An Rh person has the Rh antigen in their blood,
  rH does not.
• An Rh negative person does not have the antigen
  in the blood because both alleles are negative.

5
Huntington Disease

• A disease that causes painful progressive loss of
  muscle control and mental function until death.
• It affects people starting in their thirties and
  forties. They show no symptoms until that age.
• The gene that causes it is dominant.

6
Sickle Cell Anemia

• Also called sickle cell disease.
• Affects mainly people of west African decent.
• This is a codominant trait.
• A person with one allele for Sickle Cell is a
  carrier and does not have the disease.

7

• A carrier for sickle cell has a better resistance
  to malaria than other people.
• A person with two copies of the Sickle Cell
  allele will have the disease.
• A person with the disease has trouble moving
  enough oxygen in their blood.
• The sickle shape of the red blood cells can also
  cause painful clots.

8
Sex-linked genetic disorders

• Sex-linked traits are most common in males and
  are usually recessive.
• Examples Colorblindness, Hemophilia, and some
  forms of Muscular Dystrophy.