Nucleic Acids and Protein Synthesis

Chapter 10

I.         Nucleotides

            A.        Monomer of nucleic acid

            B.        Phosphate bound to pentose

            C.        Pentose bound to N containing base

                        1.         Purines: 2 rings, hexagon and pentagon

                        2.         Pyrimidine: single hexagon

II.        Nucleic Acid

            A.        Polymers of nucleotides

            B.        Phosphate connected to C in side chain

            C.        Phosphate binds to nr. 1 C in pentose

III.       DNA Structure

            A.        Polymer of deoxyribose nucleotides

            B.        Sugar and phosphate components identical

            C.        Bases differ

                        1.         Purines: adenine, guanine

                        2.         Pyrimidine: cytosine, thymine

            D.        H bonds between bases join chains and produce twist

            E.        Form complementary chains

                        1.         A to T

                        2.         C to G

            F.        Only one side transcribed, complement used for repair

IV.      DNA Replication

            A.        DNA helicase splits molecule at replication fork

            B.        DNA polymerase finds to split chains

            C.        Uses free nucleotide to make complement to chain

            D.        Produces molecule with old and new half

V.        Proofreading

            A.        Enzymes check new molecule for accuracy

            B.        Repair enzymes fix errors (1 in 10⁹)

            C.        Repair enzymes also fix damage

VI.      RNA Structure

            A.        Polymer of ribose nucleotides

            B.        Single strand vice double

            C.        Uracil replaces thymine

VII.     Messenger RNA (mRNA)

            A.        Single uncoiled strand

            B.        Produced by RNA polymerase from DNA code

            C.        Complement to DNA

            D.        Template for protein syntheses

VIII.    Transfer RNA (tRNA)

            A.        Single strand bent into loop

            B.        Each coded for single amino acid

            C.        Moves free amino acids to ribosome

IX.      Ribosomal RNA (rRNA)

            A.        Globular form in ribosome

            B.        Assembles protein using mRNA and tRNA

X.        Genetic Code

            A.        Correlates nucleotide sequence to amino acid sequence

            B.        Codon: sequence of 3 nucleotide

            C.        Each codon represents 1 amino acid

            D.        Same codes used by all organisms

            E.        Table 8-1 on page 121

XI.      Transcription

            A.        Process of reading code in DNA and making mRNA

            B.        RNA polymerase binds to promoter site

                        1.         Start code for gene (AUG)

                        2.         Splits helix to read code

            C.        Polymerase reads code and assembles mRNA from free nucleotides

            D.        Stops synthesis at stop code (UAG, UAA, UGA)

            E.        mRNA released and DNA helix closed

XII.     Amino Acids

            A.        Monomer of proteins

            B.        Amine group and carboxyl group bound to hydrocarbon

            C.        20 naturally occurring amino acids

            D.        Same amino acids in all organisms

XIII.    Proteins

            A.        Polymer of amino acids

            B.        Peptide bond joins

            C.        Function of protein depends on ability to bind with chemicals

            D.        Structure determines ability to bind

            E.        Sequence of amino acids determine twisting and folding

XIV.   Translation

            A.        Occurs at ribosome

                        1.         Large subunit: two binding sites for tRNA

                        2.         Small subunit: one binding site for mRNA

            B.        Ribosome small subunit binds with mRNA

                        1.         tRNA with anti codon UAC binds with start code on mRNA

                        2.         Ribosome moves one codon

            C.        Ribosome large subunit reads codon

                        1.         tRNA with coded amino acid binds large subunit

                        2.         Ribosome moves one codon

                        3.         Ribosome reads codon

                        4.         tRNA with coded amino acid binds to large subunit

                        5.         Amino acids on two tRNA molecules join (peptide bond)

            D.        Process continues until stop code reached

            E.        Ribosome releases mRNA which is recycled

            F.        Ribosome releases protein (primary structure at this point)

            G.        Secondary and tertiary structures form in ER and Golgi apparatus

XV.     Hidden Genes (Scientific American, Nov 2003)

XVI.   Old Dogma

            A.        DNA stores information and makes RNA

            B.        RNA makes protein

            C.        Proteins do the work of biology

            D.        Introns are junk

XVII.  Transcriptional Unit

            A.        Any segment of DNA that is transcribed into RNA

XVIII. New Role for RNA

            A.        Interact with:

                        1.         Proteins

                        2.         RNA

                        3.         Small molecules

            B.        RNA digital sequence

            C.        No standard start/stop code for RNA gene

XIX.   Antisense RNA

            A.        Copied from complementary strand

            B.        Bind with normal mRNA

            C.        Stop protein sysnthesis

            D.        May be used for virus protection

XX.     Micro RNA

            A.        Short non-coding RNA

            B.        Fold back unto self, hairpin shape

            C.        Treated as virus by RNA interference machinery

            D.        Results in destruction of normal mRNA

            E.        Suppresses normal genes

XXI.   RNA Enzymes

            A.        RNA-only gene produces RNA sequence

            B.        RNA binds with protein to make enzyme

            C.        Control function of mitochondria

XXII.  Riboswitches

            A.        Code for RNA in DNA between genes

            B.        Folded non-coding part

            C.        Shape of fold determines the target molecule

            D.        Coding end is blueprint for protein

            E.        Protein produced in presence of target molecule