Genes and Environment 0.0 / 5 ? BiologyGenes and the EnvironmentASEdexcel Created by: MimaCreated on: 23-02-14 19:58 Nature and Nurture Genotype = genetic makeup Phenotype = physical characteristics Can be altered by genotype and environmental factors Some phenotypes can be altered by environment e.g. blood group when controlled at a SINGLE LOCUS they show discontinuous variation fall into discrete groups with no overlap Some affected by genotype and environmental factors e.g. human height normal distribution curve (bell) controlled at SEVERAL LOCI - polygenic inheritance environment directly influences expression of the genes 1 of 4 Polygenic Inheritance Involves interaction of alleles at several loci pattern of inheritance polygenic Environmental factors often multifactoral e.g. eye colour Greater number of loci = greater number of possibilities If homozygous, alleles are the same e.g. BB BB BB or bb bb bb A punnet square shows possible outcomes of maternal and paternal gametes 2 of 4 Genes and environment interactions p1 e.g. hair colour; height; MAOA; cancer HEIGHT people are getting taller more able to reach potential height better diet less disease better heating shown that taller people have more children MAKING MELANIN dark pigment in skin/hair form in melanocutes in root follicle and skin cells activated by MSH - melanocyte stimulating hormone receptors on curface of melanocyte cells places melanin into melanosomes collect around nucleus to protect from UV light Some animals produce mutant tyrosinase - results in unstable form 3 of 4 Genes and environment interactions p2 MAOA Monoamine oxidase A - is an enzyme that catalyses breakdown of a neurotransmitter in the brain (responsible for behaviour to stress) Rare mutation produces no enzyme, results in more aggressive behaviour Kings College (london) study shows childhood maltreatment also responsible, not just MAOA production CANCER When cell production rate is faster than the rate of destruction caused by damage to DNA easily damaged by physical factors and carcinogens -carcinogens found in environment and by cell metabolism mutations can occur when cells divide cells go through G1, S, D2, M -- controlled progressions proteins stimulate the next stage --cancer cells do not respond Oncogenes code for next transition - can cause excessive cell division Tumour Suppressor Genes stop the cycle - loss causes excessive cell division 4 of 4
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