2026-03-28 20:12

Status: #new

Tags: #biology #genetics

Blood Type

Sickle-cell Anemia

• Sickle-cell anemia is a condition where the shape of a red blood cell is sickled rather than biconcave.
  • ie.
• This causes blood to clot, as the blood does not flow well in the blood vessels. Sickle Cells also break down faster than regular blood cell and can cause anemia (Reduced ability for blood to carry oxygen)

Genetic Patterns of Sickle-cells

• The sickle cell allele is co-dominant to the normal allele of blood cells. Sickle-cell anemia however is only exhibited in homozygous individuals.
  • A homozygous sickle-cell individual typically has a shortened lifespan
• Genetic Cross Example:
• ie.

Genetic Reasonings

• Sickle-cell alleles are most commonly found in African individuals, where malaria is a more common parasite infection
  • Individuals who are homozygous wild-type can succumb to malaria, which could be fatal.
  • Heterozygous individuals are a lot more resistant to malaria as it slows down the growth of parasites in sickled-individuals

Human Blood Type

• There are two types of blood type:
  • ABO blood type
  • Rhesus Factor
• Blood type is important to understand, as our immune system is built to destroy any cells which do not match those found in our own bodies
  • This means a mismatch can be fatal
• Antigens are proteins on the cell surface which antibodies recognize.
  • When a antibody recognizes a non-self antigen, the immune system is signalled to attack the cell of that antigen.

ABO blood types

• There are three different alleles that determine ABO blood type
  • 1. A Type ($I^A$ )
  • 2. B Type ($I^B$)
  • 3. O Type ($\mathrm{i}$)
• A and B blood type alleles are co-dominant to a recessive O type all
• Genetic Cross Example:

Agglutination

• Incompatible blood types often result in agglutination
• This type of blood cell cluster is undesirable

Rhesus Factor

• Two alleles determine the Rhesus Factor

  • Positive Allele $[+]$
  • Negative Allele $[-]$

• The positive allele is dominant to the negative allele

• Genetic Cross Example:

• People usually do not have antigens to rhesus factor. However, pregnant woman can develop $[+]$ antigens. This is why $[-]$ Rhesus factor is considered ideal

  • This process is known as Maternal Alloimmunization

References

2.0x Genetics