Notes on Nucleic Acids 2 types of nucleic acids: DNA – deoxyribonucleic acid RNA – ribonucleic...

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Notes on Nucleic Acids 2 types of nucleic acids: DNA – deoxyribonucleic acid RNA – ribonucleic acid Chapter 8

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  • Notes on Nucleic Acids2 types of nucleic acids:DNA deoxyribonucleic acidRNA ribonucleic acidChapter 8

  • organic compoundslarge, made of subunits called nucleotides Click image for interactive journey into human DNA

  • Each DNA nucleotide is made up of 3 parts:1. Phosphate group2. Deoxyribose 5 carbon sugar3. Nitrogen base either adenine, thymine, cytosine, or guanine

  • Nitrogen basesPurines adenine (A) and guanine (G)

  • Pyrimidines thymine (T) and cytosine (C)

  • The bases are held together by weak hydrogen bondsBase pairings in DNA:A T C G

  • A model of DNA was constructed in 1953 at Cambridge University in England

  • Scientist James Watson, (1951-1953)Field of study biologyCountry - America

  • Scientist Francis Crick (1951-1953)Field of study biophysics Country - England

  • Their model is described as a double twisted helix (looks like a twisted ladder)Watson and Crick published their proposed DNA double helical structure in a paper in the journal Nature in April 1953. In this paper Watson and Crick acknowledged that they had been "stimulated by.... the unpublished results and ideas" of Wilkins and Franklin.

  • Scientist Maurice Wilkins, (1950-1953)Field of study biophysics Country - England

  • Scientist Rosalind Franklin, (1951-1953)Field of study Molecular Biology (x-ray diffraction)Country - England Click image for interpret-ation of the X-ray

  • The process by which DNA builds an exact copy of itself - replicationfirst the double helix must be unwound this is done by enzymes called helicasesthen DNA polymerases (enzymes which move along each DNA strand) add nucleotides to the exposed bases

  • Replication occurs every time a cell divides, therefore passing the DNA code on into every cell

  • Genes are the DNA-encoded information that specifies particular proteins;Each gene is made of a specific sequence of nucleotides

  • The working structures of genes are made of RNA RNA structure:1. Consists of a single strand of nucleotides

  • 2. Ribose a 5 carbon sugar3. Uracil (U) instead of thymine (T) uracil is paired with adenine

  • RNA base pairings:A U C G

  • Three types of RNA mRNA messenger RNA2. tRNA transfer RNA 3. rRNA ribosomal RNA All are needed for processing the information from DNA into proteins (gene expression)

  • Differences in DNA and RNA:DNARNA1. double stranded single stranded2. thymine uracil3. nucleus only cytoplasm4. deoxyribose sugar ribose sugar

  • Gene expression occurs in two stages:1. Transcription information in DNA is transferred to mRNA2. Translation the information in mRNA is used to make a protein

  • Roles of DNA & RNA in transmitting genetic informationStory time: the analogyComp Book Draw the Flow Map: DNA expression in the cellYou need your pencil plus three colors:Pencil will draw cell membrane/ cell parts/ labelsRED: DNA moleculesBLUE: any RNA moleculesPURPLE: protein


  • RNA protein

  • 1. Transcription (DNA RNA) occurs in nucleusbegins with the enzyme RNA polymerase which binds to the promoter

  • Promoter a specific sequence of DNA that acts as a start signal for transcriptionTerminator a sequence of bases that tells the RNA polymerase to stop adding nucleotides

  • Transcription Video

  • mRNA is an RNA copy of a gene used as a blueprint for a proteincarries hereditary information from DNA and delivers it to the site of translationacts as a template for the assembly of amino acids

  • tRNA acts as an interpreter moleculetranslating mRNA sequences into amino acid sequences

  • rRNA plays a structural role in ribosomes

  • 2. Translation (RNA proteins) occurs in cytoplasm @ a ribosomeboth free ribosomes & ribosomes attached to ERuses nucleic acids to synthesize proteins

  • involves all three RNA types:rRNA in the ribosome

  • mRNA containing the genetic message

    message is made of codons


  • Codon a series of three-nucleotide sequenceseach codon corresponds to an amino acid or signifies a start or stop signal

  • tRNA carrying specific amino acids to be joined

  • AUG-AAA-UAC-CCU-CCA-GCG-GGAmRNAtRNAUACtRNAtRNAtRNAGGAAUGGGUProtRNAUUUribosomeMetLysTyrSerTranslation (Example)Growing polypeptide

  • Translation: mRNA, tRNA & rRNA in cooperative actionto make proteins!!!

  • AUG-AAA-UAC-CCU-CCA-GCG-GGAmRNAtRNAUACtRNAtRNAtRNAGGAAUGGGUProtRNAUUUribosomeMetLysTyrSerTranslation (Repeated)Growing polypeptide

  • Translation Video

  • A PolysomeCan you ID the 3 RNAs?

  • Awesome summary video from Click here to view