Biology Today Third Edition Chapter 3 Human Genetics Copyright © 2004 by Garland Science Eli Minkoff Pam Baker

What Do Genes Do? Direct the production of a protein –Two steps: 1.transcription of DNA to RNA 2.translation of RNA to protein together, are called gene expression Just because you have a gene for a trait doesn’t mean it will be expressed (show up)

RNA: the other nucleic acid Ribonucleic Acid How is it similar to DNA? –Made of nucleotides A sugar A phosphate Nitrogenous bases

RNA: the other nucleic acid Ribonucleic Acid How is it different from DNA? –Made of nucleotides A sugar: ribose instead of deoxyribose A phosphate: the same PO 4 Nitrogenous bases: Adenine, Cytosine, Guanine, and URACIL (no Thymine) –Single stranded

RNA: the other nucleic acid Three types….three different jobs –mRNA = messenger RNA –tRNA = transfer RNA –rRNA = ribosomal RNA

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Identifying genetic causes for traits/diseases Is the trait/disease environmental or genetic? –Lifestyle-can still be influenced by family –Studies of twins Pp. 72 to 75-discuss how a particular trait/disease might be linked to a particular gene; not testworthy

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Linkages found Huntington’s-chromosome 4 Cystic fibrosis-chromosome 7 Alzheimerj’s disease-chromosome 21 One colon cancer-chromosome 2 Two forms of manic depression- chromosome 11 and X

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Only a few follow simple Mendelian genetic processes: Alkaptonuria Phenylketonuria Duchenne’s muscular dystrophy Cystic fibrosis-chromosome 7 Huntington’s disease/chorea- chromosome 4

Some genes increase risk or susceptibility Alcoholism Obesity Some traits are governed by several to many genes Height Skin color

How can this info be used? Gather/share info through genetic testing and counseling Change individual genotype (gene therapy) Change gene pool at populational level Change balance between environmental and genetic factors

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Figure 3.12 Polymerase Chain Reaction (PCR)-Nobel-worthy discovery

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