Molecular Biology - expanding on macromolecules, DNA, RNA DNA and RNA –Macromolecules –Polymers of nucleotides –Double stranded or single stranded –Sugar-phosphate backbone …think back to Ch. 3

Nucleic Acids Polymers of 4 specific monomers = nucleotides –Via dehydration synthesis between sugars Builds chain w/sugar- phosphate backbone Single stranded RNA Double stranded DNA

RNA is similar to DNA –Except for the sugar and one base Uracil (U) in place of Thymine (T)

Structure of DNA James Watson and Francis Crick, 1953 –Rosalind Franklin Double helix

Replicating DNA Based on its structure, Watson & Crick predicted that cells copy genes by matching complimentary bases

Untwists and replicates both strands simultaneously Rapid process –Efficient –Builds in two directions Use of enzymes –DNA polymerase Links nucleotides to growing daughter strand

Link to genotype & phenotype Genotype = genetic makeup; contained in DNA Phenotype = traits; expressed from proteins –Proteins are the link…genes build proteins How? –DNA sends out instructions as RNA, which synthesizes proteins

… in other words DNA is our blueprint The boss or engineer sends a carbon copy, transcribed RNA, for construction At the construction site, the foreman (ribosomes) translates the plan to the crew, who are not trained to read the plans, but know it in terms of amino acids; the building blocks of proteins

Translating nucleic acid language to polypeptides (chains of amino acids) Nucleotides (A,T,C,G or A,U,C,G) are the alphabet Translation code –Words made of 3 letters (triplets) = codons Polypeptide language –Consists of 20 amino acids

Cracking the genetic code Rules of communicating –from RNA’s codons to amino acids in proteins

Transcribe the DNA strand: GGT-AAA-TGC ___ - ___ - ___ RNA Translate RNA into polypeptides

Transcribe the DNA strand: GGT-AAA-TGC CCA-UUU-ACG RNA Translate RNA into polypeptides Pro – Phe - Thr

Transcription –Making the RNA Occurs in steps Initiation Enzyme with start point = promoter Elongation Adds nucleotides to RNA strand Termination Enzyme reaches stop point

DNA → RNA → protein Flow of information begins in a gene –Nucleotide sequence = DNA –Serves as a template Template transcribed into –Another nucleotide sequence = RNA RNA is responsible (translation) for the next sequence –Amino acids = polypeptide Proteins formed from polypeptide determines cell appearance and capabilities

Potential to look backward From protein back to gene –E.g. Sickle cell disease caused by different amino acid in hemoglobin protein Caused by change of a single nucleotide = mutation

Mutations Types of gene mutations –Base substitution No change Positive change Harmful change (sickle cell example) –Base insertion or base deletion Alters the reading frame Very bad

Causes of mutations Errors during DNA replication Mutagens –Physical agent e.g. UV, X-rays, or gamma rays –Chemical agent e.g. ethidium bromide,