Chapter 15 Human Genetic Diversity

Chapter 15 Human Genetic Diversity - Chapter 15 Human...

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Chapter 15: Human Genetic Diversity Explaining Human Variation - Scientists distinguish two sources of human variation: genetic and environmental o Genetic variation refers to differences between individuals that are caused by the genes they inherited from their parents o Environmental variation refers to differences between individuals caused by environmental factors Ex: culture o One example of variation is body weight Environmental factors: cultural perception of beauty and the availability of food Genetic component as well - It is difficult to determine the relative importance of genetic and environmental influences for particular phenotypic traits o The problem is that both genetic transmission and shared environments cause parents and offspring to be similar o Quite different process create and maintain genetic and environmental variation among groups Identifying the source of human differences will help us understand why people are the way they are Genetic variation is governed by processes or organic evolution: mutation, drift, recombination, and selection - It is important to distinguish variation within hu m an groups from variation a mong hu m an gr o Variation within groups refers to differences between individuals within a given group of o Variation a mong groups refers to differences between entire groups of people o The causes of variation within groups can be very different from the causes of variation groups Variation in Traits Influenced by Single Genes - By establishing the connection between particular DNA sequences and specific traits, scient shown that variation in som e traits is gen etic o Ex: sickle cell an e mia is caused by one variant of he moglobin, the protein that transport m olecules in red blood cells Hemoglobin S, which causes sickle-cell ane mia replaces the a mino acid, gluta mic acid another, valine in the sixth position of the protein chain - We can prove that traits are controlled by genes at a single genetic locus by showing that th inheritance conform to Mendel’s principles o If the pattern of inheritance shows a close fit to the pattern provided by Mendel’s princip can be confident that their trait is affected by a single genetic locus Ex: Specific language impairment (SLI) causes people to have trouble learning to spe This is linked to a gen etic m arker on chromosom e 7 known as FOXP2 o FOXP2 has undergone strong directional selection since the divergence of hu m chimpanzees But, the fact that SLI is caused by a single gene doesn’t m e an that the gene is res all of the psychological m achinery in the hu m an brain that gives rise to language o The FOXP2 gene codes for a transcription factor belonging to a family of genes an important role in regulating gene expression during developm ent o It is strongly expressed in the brains of developing fetuses o SLI in other families m ay be caused by other gen es whose expression is necess norm al brain developm ent Causes of Genetic Variation within Groups
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Chapter 15 Human Genetic Diversity - Chapter 15 Human...

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