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Lecture 4

ARCL-1006EL Lecture Notes - Lecture 4: Human Genetic Variation, Ultraviolet, Calcium Metabolism

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Alice Hawkins

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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
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