As modern humans migrated out of Africa, they encountered many new environmental

Question

As modern humans migrated out of Africa, they encountered many new environmental conditions, including greater temperature extremes, different pathogens and higher altitudes. These diverse environments are likely to have acted as agents of natural selection and to have led to local adaptations. One of the most celebrated examples in humans is the adaptation of Tibetans to the hypoxic environment of the high altitude Tibetan plateau. A hypoxia pathway gene, EPAS1, was previously identified as having the most extreme signature of positive selection in Tibetans and was shown to be associated with differences in hemoglobin concentration at high altitude.

Using the two papers that are attached (with titles given below) summarize (in detail) the authors’ findings.

What is the normal function of the EPAS1 protein?

Find its protein sequence variations---can you determine any structural reason that could account for its unique activity?

Could there be gene differences?

From where did this gene originate and what are the physiological reasons as to why it would be maintained in a sub-population of modern humans?

Are there any negative aspects when hemoglobin levels are elevated in the blood?

If so, does the sub-population that possess this trait have an increased proportion of this negative response over normal populations?

Explanation / Answer

Actually is the part of the larger protein complex HIF which plays critical role in adapting the changes of oxygen levels

HIF have functions like cell division and production of RBCs and production of new blood vessels it also helps in maintaining the catecholamine balance in the heart

2.this activity is due to single nucleotide polymorphism rs56721780 G>C and insertion deletion polymorphism in the promotor region showed diverge between the tibitians and non Tibitians

3.Living at high altitudes as they have low oxygen body is forced to produce more hemoglobin hence the hemoglobin synthesis is increased

Elevated hemoglobin causes increased blood viscosity and causes peripheral cyanosis and impaired mental function as cerebral blood flow is decreased and risk of thromboembolism increases

4. Subpopulation gets adapted to these genetic changes they have increased mean hemoglobin values due to adaptive evolutionary changes

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