PS 263 Chapter 4 - Chapter 4 Genetics Evolution Development...

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Chapter 4: Genetics, Evolution, Development and PlasticityModule 4.1: Genetics and Evolution of BehaviourMendelian GeneticsMendel demonstrated that inheritance occurs through genes, units o heredity that maintain their structuralidentity form one generation to anotheroGenes come in pairs because they are aligned along chromosomesthat also come in pairsoGene has been defined as part of a chromosome composed of the double-stranded molecule deoxyribonucleic acid (DNA)A strand of DNA serves as a template for the synthesis of ribonucleic acid (RNA)molecules, a single strandchemicaloOne type of RNA molecule – messenger RNA – serves as a template for the synthesis of protein moleculesoDNA contains four “bases”AdrenalinGuanineCytosineThymineoThe orderof those bases determines the order of corresponding bases along an RNA moleculesAdenineGuanineCytosineUraciloThe order of bases along an RNA molecule in turn determines the order of amino acids that compose a proteinHomozygous - anyone with an identical pair of genes on the two chromosomesHeterozygous – an individual with an unmatched pair of genesDominant gene shows a strong effect in either the homozygous or heterozygous conditionRecessive gene shows its effects only in the homozygous conditionSex-Linked and Sex-Limited GenesSex-linked genes - the genes on the sex chromosomes; X or Y chromosomeAutosomal genes – all other chromosomes When biologists speak of sex-linked genes, they usually mean X-linked genes because Y chromosome is small, with genes for far fewer proteins than other chromosomesSex-limited genes– is on autosomal chromosome, but activated in one sex more than in the otherGenetic ChangesMutation– heritable change in a DNA moleculeoChanging just one base in DNA to any of the other three types means that the mutant gene will code for a protein with a different amino acid at one location in the moleculeoMutation is rarely advantageousAnother kind of mutation is a duplication or deletionoDuring the process of reproduction, part of a chromosome that ordinarily appears once might instead appear twice or not at alloWhen this process happens to just a tiny portion of chromosome, we call it a microduplicationor microdeletionoAlthough it is possible for a duplication to be helpful, microduplications and microdeletions of certain brain-relevant genes are a possible explanation for schizophrenia
EpigeneticsEpigenetics – this field deals with changes in gene expressionoEpigenetic changeis an increase or decrease in the activity of a gene or group of genesoThe activity of a gene can vary:The genes active in our brain are not the same as those active in your lungs or kidneys At puberty, certain genes that had been almost silent become much more activeVarious (environmental) experiences can turn a gene on/offo

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