Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Notes on Nucleic Acids Chapter 8 2 types of nucleic acids: DNA – deoxyribonucleic acid RNA – ribonucleic acid • organic compounds • large, made of subunits called nucleotides Click image for interactive journey into human DNA Each DNA nucleotide is made up of 3 parts: 1. Phosphate group 2. Deoxyribose – 5 carbon sugar 3. Nitrogen base – either adenine, thymine, cytosine, or guanine Nitrogen bases Purines – adenine (A) and guanine (G) Pyrimidines – thymine (T) and cytosine (C) The bases are held together by weak hydrogen bonds Base 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 – biology Country - America Scientist – Francis Crick (1951-1953) Field of study – biophysics Country - England Their model is described as a double twisted helix 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 the unpublished results and ideas" of Wilkins and Franklin. (looks like a twisted ladder) 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 interpretation of the X-ray The process by which DNA builds an exact copy of itself - replication • first the double helix must be unwound – this is done by enzymes called helicases • then 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 sugar 3. Uracil (U) instead of thymine (T) uracil is paired with adenine RNA base pairings: A – U C–G Three types of RNA 1. mRNA – messenger RNA 2. 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: DNA RNA 1. double stranded single stranded 2. thymine uracil 3. nucleus only cytoplasm 4. deoxyribose sugar ribose sugar Gene expression occurs in two stages: 1. Transcription – information in DNA is transferred to mRNA 2. Translation – the information in mRNA is used to make a protein Roles of DNA & RNA in transmitting genetic information • Story time: the analogy… • Comp Book– Draw the Flow Map: DNA expression in the cell • You need your pencil plus three colors: – – – – Pencil will draw cell membrane/ cell parts/ labels RED: DNA molecules BLUE: any RNA molecules PURPLE: protein DNA RNA RNA protein 1. Transcription (DNA RNA) • occurs in nucleus • begins with the enzyme RNA polymerase which binds to the promoter Promoter – a specific sequence of DNA that acts as a “start” signal for transcription Terminator – 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 protein • carries hereditary information from DNA and delivers it to the site of translation • acts as a template for the assembly of amino acids tRNA – acts as an interpreter molecule • translating mRNA sequences into amino acid sequences rRNA – plays a structural role in ribosomes 2. Translation (RNA proteins) • occurs in cytoplasm @ a ribosome —both free ribosomes & ribosomes attached to ER • uses nucleic acids to synthesize proteins • involves all three RNA types: —rRNA in the ribosome —mRNA containing the genetic message AUG-AAA-UAC-CCU-CCA-GCG-GGA —message is made of codons Codon – a series of three-nucleotide sequences • each codon corresponds to an amino acid or signifies a start or stop signal Write this down! —tRNA carrying specific amino acids to be joined a.a. Translation ribosome mRNA (Example) AUG-AAA-UAC-CCU-CCA-GCG-GGA UAC GGU tRNA UUU AUG tRNA Growing polypeptideGGA Met tRNA Lys tRNA tRNA Tyr Pro Ser Translation: mRNA, tRNA & rRNA in cooperative action …to make proteins!!! Translation ribosome mRNA (Repeated) AUG-AAA-UAC-CCU-CCA-GCG-GGA UAC GGU tRNA UUU AUG tRNA Growing polypeptideGGA Met tRNA Lys tRNA tRNA Tyr Pro Ser Translation Video A “Polysome” Can you ID the 3 RNAs? Awesome summary video from www.youtube.com Click here to view