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Molecular Genetics gene: specific region of DNA that determines the type of proteins to be made Nucleic Acids – serve as blueprints for the construction of proteins Two Types 1) DNA (DeoxyriboNucleic Acid) 2) RNA (RiboNucleic Acid) Nucleic Acids nucleotides: monomers that combine to form nucleic acids Three Parts of a Nucleotide 1) • DNA has 4 nitrogen bases: • Adenine A • Thymine T • Cytosine C • Guanine G • DNA has deoxyribose as its sugar • RNA also has 4 nitrogen bases: • Adenine A • Uracil U • Cytosine C • Guanine G • RNA has ribose as its sugar What does DNA & RNA look like? • Rosalind Franklin - worked with X-ray photos of DNA • James Watson & Francis Crick - Nobel prize for deciphering structure of DNA RNA = single polynucleotide strand DNA = double helix; 2 polynucleotides wrap around each other (“spiral stairs”) What does DNA & RNA look like? In DNA, the 2 polynucleotides pair up & bond (H-bond) at nitrogen bases: Complementary Base Pairing in DNA Adenine --- Thymine (A – T) Cytosine --- Guanine (C – G) • Long strands of DNA with A-T & C-G base pairing is at the core of genetics, • Therefore, in Interphase when chromosomes are replicated, DNA is also replicated How is DNA replicated? Template Hypothesis • Two strands of parent molecule of DNA separate • Separated strands now serve as a “template” for free nucleotides to attach; remember nucleotides must match up (A-T or C-G) Template Hypothesis DNA polymerase: primary enzyme involved in assembling DNA molecules; also checks for errors (wrong base pairing) DNA Replication What is a ‘genotype’ or ‘phenotype’ in molecular language? • Genotype is gene (DNA) makeup of organism Two Main Stages of Protein Synthesis 1) Transcription: 2) Translation: • Phenotype is a physical trait of an organism • determined by specific proteins with specific functions e.g., some structural proteins comprise hair, therefore, different ‘hair proteins’ determine different hair traits (color, curly, straight, coarse, fine, etc…) • codon: 3-base code that are used to produce amino acids • amino acids = Transcription: DNA to RNA * Base pairing of RNA nucleotides using DNA template (note pairings) – RNA polymerase Transcription: • Nucleotide sequence in DNA starts transcription process promoter -- Transcription: • 2nd Phase = RNA elongates • RNA begins to separate from DNA template • DNA strands begin to reattach Transcription: • 3rd Phase – RNA polymerase reaches end of gene Transcription: • For eukaryotes, newly formed RNA molecule is modified to produce messenger RNA (mRNA) mRNA Transcription: • Also remove introns (noncoding region) • Resplice exons (coding region = genetic information that is ultimately expressed as trait • mRNA now leaves nucleus mRNA Transfer RNA (tRNA) • Serves as translator between mRNA and ribosomes • In other words, tRNA translates nucleic acid language (codons) into protein language (amino acids) • anticodon: complement to mRNA codon tRNA ribosomes Translation Summary of transcription & translation - 1 Summary of transcription & translation - 2 HIV AIDS • HIV has 2 strands of RNA • Reverses normal transcription process (retrovirus) Evolution • Charles Darwin • Evolution: Evolution • Charles Darwin • Evolution: Descent with Modification •Look at the fossil record… Macroevolution * Major biological changes in species (found in fossil record) Speciation: origin of new species Evolution • Look at the fossil record… • Compare common structures in animals, e.g., forelimbs in human, cat, whale and bat • (homologous structures) • * Principles of Darwin’s Thinking 1) All organisms vary from one another & some variations are heritable 2) All organisms have potential to produce many young. 3) Limited resources influence number of young that survive to reproduce Natural Selection • Primary theoretical mechanism of evolution • Deals with differential (unequal) survival & reproduction • “Survival of the Fittest” Natural Selection Population Genetics Microevoltion gene pool: all of the genes in a population at one time; includes all alleles • At population level, look for change in allele frequencies over time. • If allele frequencies change, gene pool is changing & microevolution is occurring. Population Genetics Hardy-Weinberg Equilibrium * Hypothetical, non-evolving population * No change in allele frequencies Assumptions: 1) No Natural Selection 2) No Mutation of genes 3) No Migration/No Gene Flow 4) LARGE Population 5) Random Mating Population Genetics How does Microevolution Occur in a Population? Five Possible Mechanisms Small Populations genetic drift: certain alleles lost due to chance events Genetic Drift Small Populations bottleneck effect: some event unselectively removes large part of population; remaining individuals may be genetically similar & subject to genetic drift Bottleneck Effect Small Populations founder effect: