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This 3 page Class Notes was uploaded by Kiara Reyes on Sunday August 28, 2016. The Class Notes belongs to Bio 308 at Northern Illinois University taught by M. Johns in Summer 2016. Since its upload, it has received 12 views. For similar materials see Genetics in Biology at Northern Illinois University.
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Date Created: 08/28/16
Bio 308 Lecture 1: History of Genetics History of Genetics People have known about inheritance for a long time Ex: -Children resemble their parents Ex: -Domestication of animals and plants, selective breeding for good characteristics ~Old Ideas~ Despite knowing about inheritance, a number of incorrect ideas had to be generated and over come before modern genetics could arise 1. All life comes from other life. Living organisms are not spontaneously generated from non-living material. Big exception: origin of life 2. Species concept: offspring arise only when two members of the same species mate. Hybrids don’t exist 3. Organisms develop by expressing information carried in their hereditary material. As opposed to preformation: idea that each sperm (or egg) is a tiny fully-formed human that merely grows in size 4. The environment can’t alter hereditary material in a directed fashion. No inheritance of acquired characteristics; a.k.a “Mutations are random events” 5. Male and female parents contribute equally to the offsrpings Molecular Reality (Current View) Almost all inheritance is based on DNA: the sequence of ACGT nucleotides encodes all instructions needed to build and maintain an organism Chromosome- single DNA molecule together with other molecules (proteins and RNA) needed to support and read DNA Gene- specific region of a chromosome that codes for a single polypeptide (linear chain of amino acids) Proteins- composed of one or more polypeptide, plus in some cases other small helper molecules (co-factor) Gene Expression Genes are expressed in a 2 step process: 1. Transcription- an RNA copy a single gene in made 2. The nucleotide sequence of the RNA copy (messenger RNA) is Translated into the amino acid sequence of the polypeptide 3. Genetic Code is a list of which 3 base DNA or RNA sequence (codon) encodes which amino acid. All cells in the body have the same DNA, but different genes are expressed in different cells and under different conditions Gene Difference Genes often have several alleles: the same gene in the same chromosomal location, but the minor nucleotide changes that yield slightly differently proteins For a given gene, many different alleles can exist in a population (members of the same species) but an individual diploid organism can have 2 alleles at most- one from each parent Chromosomal DNA contains other things beside genes: -Centromere (mitotie spindle attaches) -Telomeres (special structures on end of chromosomes) -Origins of replication (copying of DNA starts) -Pseudogenes (non-functional, mutated copies of genes) -Transposable elements a.k.a transposons (intranuclear parasites) -Genes that make small RNAs and not proteins -“Junk” or “extra parts” Mutation Mutations (which are any change in the DNA base sequence) occur constantly in all cells and organisms. Offspring rarely get a perfect copy of the DNA from its partners Some mutational changes are much longer: chromosome rearrangement that includes genes torn in half and moved to new locations, sometimes combined with other genes Prokaryotes vs Eukaryotes Prokaryotes -Bacteria and Archaea -No internal membrane-bound compartments: DNA floats free in cytoplasm -1 circular chromosome -Reproduction usually asexual -Sexual processes (mixing DNA from 2 individuals) occur, but with unequal contributions from the 2 parents -Transcription and Translation simultaneous Eukaryotes -Plants, animals, fungi, protists. Often multicellular -DNA contained within a membrane-bound nucleus -Linear chromosomes -Careful division of chromosome in cell division: mitosis and meiosis -Transcription separated from translation -Sexual reproduction: 2 parents contribute equally to offspring -Life Cycle: alternation of haploid and diploid phases Evolution Fitness- ability to survive and reproduce. An individual’s fitness is affected by its genes Natural Selection- more fit individuals tend to increase their numbers each generation, at the expense of tend to take over in the population, causing a loss of less fit genes
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