IMED2004 Study Guide - Final Guide: Selective Sweep, Melanin, Dermis
Document Summary
Individuals in a population show variation in many characters. Adaptations provide protection to certain diseases, diet etc. Adaptations risen due to altered environment in different populations. Altered environment -> adaptations -> genetic variation. Reduced uv exposure, so some populations decrease pigmentation and decrease melanin in skin to allow easier transmission of depleted uv into deep layer of dermis. Protect from hypoxia by lowering hb levels. These genetic variance increase -> become fixed. Positive selection can leave distinctive signatures of genetic variation. Expect to find hundreds of thousands of different genetic variants. Advantageous variant arises on one copy of chr 22. If subjected to strong selection, people have higher survival. Descendants carrying variant more and more common. Natural selection/positive selection can leave signatures of genetic variation. Strong selective sweep acting on an advantageous dna variant. Subjected to positive selection to maximise genetic variation. Strong selection pressure: emergence of mutant pathogens that seek to evade mhc-mediated detection.
