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Lecture 4


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Health Studies
R Song

Variations in Human Growth and Development (Height and Physiological Growth) Humans - 99.9 % identical DNA sequence level difference amongst them Chimps: 2 – 3x difference Orangutans: 8 – 10x  Genotype: o DNA sequence level comparison o Adenine-cytosine-guanine-thymine pairs and their order and such  Phenotype: o Physical manifestation of genotype o Appearance = expression of genes, but also of environment o In humans, a lot of phenotypic difference based on very little genotypic difference  Therefore, environment has a pretty big effect  Ex. place with less sunlight = lighter skin to absorb more nutrients from sun  Rules: o Warmer climates = thinner, taller proportions because better adapted to sweat (more surface area) and less fat to keep you hot o Colder climates = stockier, shorter because body fat to keep warm  Comparative Growth: o Skeletal measures (height, proportions)  Easiest to see  Graph can be stretched horizontally/vertically = the plasticity of height  Bogin: easy to attribute to genetics, but clearly more factors affect it than that  total height – sitting height = leg length  grow fastest during childhood  better childhood = longer legs  shorter sitting height  weight/height – poor nutritional status = reduced height, also reduced weight for height (changing today for obesity, will be talked about more in depth later lecture)  late-maturing kids = reduced peak height velocity vs. early-maturing kids  children w/ slow growth prior to puberty will have longer-lasting growth spurt during adolescence than children with greater prepubertal % of adult height  areas of endemic chronic undernutrition, disease, child labour: height of every age is reduced compared with less stressed pops; but total span of growth period is prolonged (i.e. up to 25/26 vs. at 18/21) o Dental development (eruption)  Can count bands of enamel in tooth to infer ages of children (growth rings)  A. American kids have advanced development of teeth vs. E. American kids  Could be mostly genetic, but could also be some kind of populational difference o Body composition (fat, muscle)  Subcutaneous fat layer = how much the body stores  Upper arm length  Triceps skin fole (TSF) o Extremity fat o Fat is more stored in trunk, so kid with trunk fat better than kid with no trunk fat o Trunk fat: subscapular skin fold thickness  (mid-)upper arm circumference (M)UAC)  High SES vs. Low SES = Higher fat in HSES thatn LSES o Girls have more body fat than boys o Sexual maturation (menarche)  Boys: growth of sex organs; pubic/body/facial hair, voice change, seminal emissions  Girls: growth of breasts, pubic/body hair, menarche, development of internal/external sex organs  Tanner Classification System
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