Molecular Genetics gene: specific region of DNA that determines the type of proteins to be made * Therefore, DNA is a type of genetic material, passed on parent to offspring

Nucleic Acids – serve as blueprints for the construction of proteins Two Types 1) DNA (DeoxyriboNucleic Acid) 2) RNA (RiboNucleic Acid) nucleotides: monomers that combine to form nucleic acids Three Parts of a Nucleotide 1) Sugar 2) Phosphate Group 3) Nitrogen Base

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 polynucleotide = nucleic acid polymer; many nucleotides

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) Enzymes work to link nucleotides together; new DNA is made New DNA molecule (daughter DNA) identical to parent DNA

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 DNA oversees protein synthesis DNA sends instructions in form of RNA RNA programs cell to make certain protein

Two Main Stages of Protein Synthesis 1)Transcription: DNA sending instructions in the form of RNA; DNA transfers genetic information to RNA 2) Translation: RNA transfers the information into protein synthesis

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 = monomers = building blocks for proteins

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 -- RNA polymerase attaches here

Transcription: 2 nd Phase = RNA elongates RNA begins to separate from DNA template DNA strands begin to reattach

Transcription: 3 rd Phase – RNA polymerase reaches end of gene = another unique nucleotide sequence in DNA (terminator)

Transcription: For eukaryotes, newly formed RNA molecule is modified to produce messenger RNA (mRNA) mRNA = extra nucleotides on ends (caps/tails)- protection 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) RNA used as template to make DNA New DNA made now has AIDS virus genetic information & cells of infected individual now make more AIDS virus

Evolution Charles Darwin Evolution: 1)Change in gene (allele) frequencies in a population

Evolution Charles Darwin Evolution: 1)Change in gene (allele) frequencies in a population 2)Modern organisms descended from ancient organisms (shared traits)

Descent with Modification

Look at the fossil record…

Macroevolution * Major biological changes in species (found in fossil record) Speciation: origin of new species Non-branching Evolution vs. Branching Evolution

Evolution Look at the fossil record… Compare common structures in animals, e.g., forelimbs in human, cat, whale and bat (homologous structures) * Common structures because of common ancestor

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” Those able to survive & reproduce, will pass on their unique DNA to next generation

Natural Selection Thus, evolution does not occur with an individual, rather it does occur at population level

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 1)Natural Selection 2)Mutation of genes = DNA changes = new alleles formed 3)Gene Flow 4)Population is small 5)Nonrandom Mating

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: few individuals colonize a new area; small, new population subject to genetic drift