Sickle Cell Trait

Definition

Sickle cell trait refers to the condition in which an individual carries one copy of the sickle cell gene (HbAS) but does not exhibit the symptoms of sickle cell disease. This trait can provide a protective advantage against malaria, making it beneficial in regions where malaria is prevalent, while also being a carrier of the genetic mutation that can lead to sickle cell disease if two copies are inherited.

5 Must Know Facts For Your Next Test

1. Individuals with sickle cell trait typically do not experience health problems related to sickle cell disease but can pass the gene on to their offspring.
2. The presence of sickle cell trait is most commonly found in individuals of African, Mediterranean, Middle Eastern, and Indian ancestry due to the historical prevalence of malaria in these regions.
3. People with sickle cell trait can experience complications under extreme physical exertion or high altitudes, although these cases are rare.
4. Sickle cell trait is inherited in an autosomal recessive pattern, meaning a person needs to inherit one copy of the sickle cell gene from each parent to develop sickle cell disease.
5. The protective effect of sickle cell trait against malaria is thought to be due to the altered shape and function of red blood cells that disrupts the lifecycle of the malaria parasite.

Review Questions

• How does sickle cell trait provide a selective advantage in populations where malaria is prevalent?
  • Sickle cell trait provides a selective advantage because individuals with this trait (HbAS) have some protection against malaria. The presence of the sickle-shaped cells makes it harder for the malaria parasite to thrive within their blood, reducing the likelihood of severe illness. This advantage increases the survival rate in areas where malaria is common, leading to a higher frequency of the sickle cell gene in those populations.
• Discuss the implications of inheriting sickle cell trait for family planning and genetic counseling.
  • Inheriting sickle cell trait has significant implications for family planning and genetic counseling. Couples where both partners have sickle cell trait face a 25% chance with each pregnancy of having a child with sickle cell disease (HbSS). Genetic counseling can help these couples understand their risks and explore options such as prenatal testing and informed reproductive choices to manage potential outcomes associated with sickle cell disease.
• Evaluate how positive selection for sickle cell trait influences genetic diversity and population dynamics in affected regions.
  • Positive selection for sickle cell trait enhances genetic diversity in affected regions by maintaining a balance between carriers and those with full-blown sickle cell disease. This dynamic allows for greater resilience in populations facing malaria, as carriers have increased survival rates. The presence of both normal and sickled hemoglobin alleles within these populations contributes to a diverse gene pool, which can be beneficial for adapting to various environmental pressures over time.

Related terms

Sickle Cell Disease: A genetic disorder characterized by the production of abnormal hemoglobin (HbS), leading to distorted red blood cells that can cause various health complications.

Malaria: A mosquito-borne infectious disease caused by parasites that infect red blood cells, often leading to severe health issues and even death.

Homozygous: An individual with two identical alleles for a specific gene, which in the case of sickle cell disease refers to having two copies of the sickle cell gene (HbSS).