ARCL-1006EL Lecture Notes - Lecture 4: Human Genetic Variation, Ultraviolet, Calcium Metabolism
16 Jun 2018
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ARCL 1006
Jan 24, 2018
Human Biological Variation Race
•Cline: gradual change in frequency or occurrence of something over space
•Contributors to variation in skin colour
•Oxidized hemoglobin (red, from red blood cells)
•melanin produced by melanocytes in epidermis
•MC1R- coded gene
•skin colour is polygenic- not a mendelian trait. There are several genes that contribute to
skin colour
•Advantages of dark coloured skin in low latitudes (close to equator // higher amounts of UVR)
•ultraviolet radiation - sunburn, skin cancer
•Meaning blocks UVR
•Ex) skin cancer
•males in Britain 28:100,000
•males in australia 265: 100,000
•Folate (B Vitamin) needed for DNA synthesis ad cell replication
•exposure to UVR - breakdown of folate
•Melanin helps filter out UVR preventing breakdown of folate
•lack of folate cause birth defects
•Advantages of light coloured skin in high latitudes
•Vitamin D needed for calcium metabolism for normal development of bones and teeth
•UVR causes a reaction in the skin that leads to production of vitamin D
•Lack of vitamin D - RICKETS
•rate of rickets in the 1920s for African American children 2-3x higher than for European
American children
•Ability to produce lactase in adulthood
•Lactase- necessary to break up lactose into glucose and galactose
•lactose- sugar made up of two smaller sugars
•Another example of a cline-
•Frequency of the alleles A, B, O for blood groups in humans.
•Neutral human genetic variation
•Arises largely from genetic drift
