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Human Biology
Stephen Wright

Chapter 1 Genetics – the study of all aspects of genes - Molecular genetics – deals with one or a few genes at once - Genomics – the study of complete gene sets (genomes) Diploid organisms – contain 2 identical sets of chromosomes - Haploid number (n) – amt of chromosomes in the basic genomic set - Humans – n = 23, 2n = 46 Electrophoresis will show that there are as many DNA bands as the haploid chromosome #, so each chromosome must only contain 1 DNA molecule - DNA is packaged very efficiently – double helix coiled around nucleosomes (molecular spools composed of 8 histone proteins) - Scaffold helps organize 3D structure of a chromosome – DNA/nucleosome coil called chromatin o Centromere – attachment point which moves the chromosome during cell division o Telomere – tips of chromosomes Prokaryotes have no nuclei; their genomes are a single noncoiled chromosome, usually circular Structural proteins – contribute to outward physical structure, e.g. hair, muscle Enzymatic proteins – catalyze rxs w/in cells that make all types of molecules Regulatory proteins – turn gene activity on/off at appropriate times/places DNA is the information storage system for almost all organisms, but the genetic coding language is pretty much the same as well - All organisms shared a common ancestor, resulting in these similarities Transcription – process of copying the DNA of a gene to make RNA (where U replaces T) - Introns are usually excised to form mRNA (messenger RNA) to convey information to the protein-generating machinery Translation – each mRNA is translated into one specific protein; DNA  RNA  protein - Polypeptide – a long chain of amino acids (20 main ones), combinations of which give each protein a unique shape/function - AA sequences formed when codons (groups of 3 nucleotides) which represent the AAs are “read” from end to end by the ribosome - Linear sequence of nucleotides  linear sequence of amino acids  specific protein Functional RNAs are never translated into proteins, but have their own important roles - rRNA (ribosomal RNA) – part of ribosomes - tRNAs (transfer RNAs) – carries amino acids to translational system Different sets of genes must be active in cells of different types in order to achieve the differentiation seen in all the body’s cells Mutations may cause differences in people’s DNA; can occur naturally or due to environmental agents like high radiation - Most mutations are bad, but some have neutral or even beneficial effects Epigenetic changes – nongenetic changes in DNA that can be passed down to future generations - Environmental exposure can affect gene function, often in a negative way Natural selection – the process by which individuals with a particular characteristic (e.g. better vision) will reproduce better than others in a given environment - Since these individuals will have more offspring, the frequency of that trait will increase Homology – similarity due to shared ancestry from a common ancestor Genetics have significantly contributed to our understanding of evolution, so knowledge of evolutionary homology allows us to extrapolate from one species’ genetic system to another - The chimpanzee is the human’s closest living relatives (supports Darwin’s hypothesis that humans evolved from apes) - DNA from bones has shown that the Neanderthal genome sequence is even closer to ours, e.g. both humans and Neanderthals have the same form of a gene for speech Forward genetics – mutation  gene discovery  DNA sequence/function - Treat cells of normal wild type form with anything that causes mutations, e.g. X-rays - Descendants of these cells are screened for abnormal manifestation of function in question - Are these properties inherited as a single mutated gene? Each presumptive mutant organism
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