BCHM 3050 1st Edition Lecture 28 Outline of Last Lecture I Mutations a Substitution b Frameshif II Chromosome Level Mutations III Mechanisms for Point Mutations IV Transition and Transversion Mutation Outline of Current Lecture I Eugenic Movement II Historical Case III History of Skin Color IV The Yin and Tang of Radiations V Melanocytes Make Melanin VI Sub Saharan Africans adapted to have darker skin VII Adaptation permitting light skin color VIII Golden Fish versus Black Pigmented Fish Study Current Lecture I Eugenic Movement a b c d e II Eugenics movement in science 1883 coined in England by Sir Francis Galton a cousin of Charles Darwin Greek word meaning well born or of good origins or breeding Science of improving qualities of race The Triangle of life Environment education heritage Historical Case a Woman was diagnosed with feeble mindedness IQ of 56 and was sterilized so that she could not have any more kids and pass on the traits of feeble mindedness b This is a failure in the field of science III History of Skin Color a Close to the equator skin color is darker b Far away from the equator skin color is lighter c Migration of our ancestors out of Africa first establishment of civilization i Migrated out 100 000 years ago IV The Yin and Tang of Radiations These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute a Vitamin D production proportional to light penetration b Folic acid Vitamin B9 destruction proportional to light penetration i Too much radiation destroys folic acid ii Expecting mothers need folic acid to allow for development of spinal chord and maxillary features in child without folic acid child my die iii In order for the people of Africa to adapt and not lose too much folic acid they had extremely dark skin because of the harsh sunlight allows them to not absorb as much sunlight and maintain folic acid levels 1 Dark skin caused by high levels of melanin c Closer to the equator has more exposure to high amount of UV radiation d UV radiation causes cross links and damages in DNA e The darker the skin do not absorb as much UV radiation V Melanocytes Make Melanin a More melanocytes more melanin b When people with dark skin moved away from harsh sunlight they could not absorb the little bit of sunlight needed to aid them with melanin i Over time the people adapted to have lighter skin color in order to be able to obtain melanin VI Sub Saharan Africans adapted to have darker skin a Mutation in MC1R a gene responsible for melanin production allowed positive selection for dark skin in early sub Saharan Africans about 130 000 years ago b When we evolved from monkeys lost hair and had light pink skin so we needed to adapted to obtained dark skin color VII Adaptation permitting light skin color a b c d e VIII Many genes control melanin levels Vitamin D UV light makes Vitamin D Folic Acid Vitamin B9 UV light destroys vitamin B9 Lots of sunlight Africa increased melanin Cold less sunlight N Europe less melanin Golden Fish versus Black Pigmented Fish Study a How was the gene responsible for the golden phenotype identified i Positional cloning identify where a particular gene is cloning all genes until I locate the position of the gene of interest ii Slc24a5 is the gene responsible for golden color b Knock down using morpholinos i Morpholinos prevent mRNA from being expressed ii Used in reverse genetics morpholinos are synthetic oligonucleotides which can bind RNA sequences thereby blocking translation iii Synthetic RNA molecule which is designed to bind to RNA to prevent it from getting translated iv Can make a morpholino target a specific position in cell v Prevent mRNA from getting translated vi Knockdown of slc24a5 with morpholinos in wildtype larvae phenocopies the golden mutation vii Wild type fish without mutations viii Golden larvae lack melanin pigments ix Wild type larvae injected with slc24a5 morpholinos wild type larvae started looking like golden larvae x Shows that this gene is responsible for pigment in zebrafish also responsible for skin color in humans 1 By removing one gene fish lost its melanin c RNA in situ hydridization to detect RNA in zebrafish larvae i Take cell and make an RNA glow ii Send a color that attached to the RNA of interest iii Add digoxigenin labeled probe into cell and it attached to mRNA send another enzyme to make it glow able to locate where the mRNA is now because it is colored iv Wildtype fish could pick up the dye color but the golden fish couldn t because they lacked the gene needed for the color to bind to v Sent probe to seek out a gene but it was not present in the mutant showed scientists to determine that that gene was responsible for melanin production d How is this study relevant to human populations i Homology studies indicated that the human slc24a5 gene also is an ion transporter 1 Search human gene pool for a similar gene and found that humans have the same gene 2 African decent Ala 111 on slc24a5 gene 3 European Thr 111 on slc24a5 gene 4 That change of one amino acid is contributes to the difference in skin color ii Within this gene only a single SNP exists where the nucleotide G is converted to A iii Allele of slc24a5 with the nucleotide G codes for Alanine at position 111 iv Allele of slc24a5 with nucleotide A codes for Threonine at position 111 v Dark skin a G from mom and dad vi Intermediate skin color G from one parent and A from another vii Light skin A from mom and dad viii Skin color does not make you a fast runner
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