Blood Type Inheritance

Basics of Blood Type Alleles

• Blood types are determined by specific alleles.
• Major blood types include A, B, AB, and O.
• Alleles include:
  • A allele (dominant) represented as I^A
  • B allele (dominant) represented as I^B
  • O allele (recessive) represented as i

Homozygous vs. Heterozygous Parents

Parent with Blood Type A (Homozygous)

• If a parent is homozygous for blood type A (I^A I^A):
  • They have two A alleles.
  • All children will inherit an A allele from this parent.
  • Conclusion: All children will be blood type A.

Parent with Blood Type O (Homozygous)

• If the other parent is homozygous for blood type O (i i):
  • They have two O alleles.
  • All children will inherit an O allele from this parent.
  • Therefore, all children will receive one A allele and one O allele, resulting in a blood type A.

Heterozygous Blood Type A Parent

• If the blood type A parent is heterozygous (I^A i):
  • They have one dominant A allele and one recessive O allele.
  • They produce two types of gametes:
  • Half will carry the dominant A allele (I^A).
  • Half will carry the recessive O allele (i).
• If paired with a blood type O partner (i i):
  • Half of their children could inherit (I^A i) and thus be blood type A.
  • Half of their children could inherit (i i) and thus be blood type O.

Blood Type B Inheritance

Parent with Blood Type B (Homozygous)

• If an individual has two alleles for blood type B (I^B I^B):
  • All children will receive a B allele.
  • Since B is dominant to O, all children will be blood type B if the other parent is type O.

Heterozygous Blood Type B Parent

• If the blood type B parent is heterozygous (I^B i):
  • They will produce:
  • Half of the gametes with the B allele (I^B).
  • Half with the recessive O allele (i).
• If the other parent is type O (i i):
  • Half of their children will be blood type B (I^B i).
  • The other half will be blood type O (i i).

Blood Type AB Inheritance

• Both A and B alleles are dominant and do not counteract each other:
  • An individual receiving one A allele (I^A) from one parent and one B allele (I^B) from the other will have blood type AB.
• Example Scenario:
  • If both parents are heterozygous (I^A i and I^B i):
  • Possible outcomes for their children:
    • Blood type A (I^A i)
    • Blood type B (I^B i)
    • Blood type AB (I^A I^B)
    • Blood type O (i i)

Summary of Blood Type Outcomes

• Parent Type A (Homozygous) + Parent Type O (Homozygous): All children will be type A.
• Parent Type A (Heterozygous) + Parent Type O (Homozygous): Children may be type A or type O.
• Parent Type B (Homozygous) + Parent Type O (Homozygous): All children will be type B.
• Parent Type B (Heterozygous) + Parent Type O (Homozygous): Children may be type B or type O.
• Parent Type A (Heterozygous) + Parent Type B (Heterozygous): Children may be type A, B, AB, or O.