Transcript Slide 1
Nucleic Acids Big Idea 3: Living systems store, retrieve, transmit, and respond to info essential to life processes. Essential Knowledge • 3A1: DNA, and in some cases RNA, is the primary source of heritable information. Nucleic Acids • Store and transmit hereditary information • Amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene • Genes are found on chromosomes. Nucleic Acids •Large, complex molecules composed of C, O, H, N, and P. •2 types are RNA, ribonucleic acid and DNA, deoxyribonucleic acid. DNA RNA Prokaryotes • Earliest cells • Smaller than Eukaryotes! • No nucleus (home for DNA) Prokaryotic DNA • Is housed in a region called the nucleoid Prok. DNA • Is usually small and circular • Has plasmids: small, extrachromosomal, double stranded, and circular DNA Viruses and Eukaryotes can have plasmids too… Herstory • Rosalind Franklin: British scientist (working in Maurice Wilkins lab) who took an X ray diffraction image of DNA, 1952 • Led to double helix shape discovery by Watson and Crick Photo 51 HIStory • Watson and Crick used Franklin’s image to create the double helix DNA model in 1953. • Won Nobel Prize in 1962,w/ Wilkins. Double Helix Structure Nucleic Acid Structure • Made of nucleotides; both RNA and DNA. Each nucleotide contains: • 1 Phosphate Group • 1 Sugar • 1 Nitrogen Base Phosphate • PO4 • Makes up a part of the DNA/RNA backbone Sugar • In DNA, sugar is deoxyribose • In RNA, sugar is ribose • Binds to Nitrogen Base • Is in backbone of DNA/RNA Fig. 5-27c-2 Sugars Deoxyribose (in DNA) (c) Nucleoside components: sugars Ribose (in RNA) DNA Nitrogen Bases • • • • Adenine Thymine Guanine Cytosine Conserved Through Evolution! DNA Base Pairing Rules (Chargaff’s Rules) • A only binds with T • C only binds with G • H bonds hold Nitrogen bases together RNA Nitrogen Bases • • • • • Adenine Cytosine Guanine Uracil NO Thymine! Fig. 5-27c-1 Nitrogenous bases Pyrimidines Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Pyrimidines: Single Ring Structure: CTU Purines Adenine (A) Guanine (G) (c) Nucleoside components: bases Purines: Doublenitrogenous Ring Structure, GA DNA: Double Stranded, RNA Single Stranded DNA is AntiParallel Fig. 5-27ab 5' end 5'C 3’ carbon and 5’ carbon bind to PO4 phosphodiester linkage 3'C Nucleoside Nitrogenous base 5'C Phosphate group 5'C 3'C (b) Nucleotide 3' end (a) Polynucleotide, or nucleic acid 3'C Sugar (pentose) DNA Replication • DNA provides directions for its own replication ensure continuous inheritance of DNA DNA Replication • Before a cell divides must duplicate its DNA. • Each strand of DNA will serve as a template/model for a new strand of DNA (semiconservative). DNA Replication st 1 Step DNA Helicase • Enzyme called DNA helicase unzips and unwinds a portion of DNA. • Enzyme helps breaks apart H connect N bases. (A,T,C,G) DNA Replication: 2nd Step • 2nd enzyme called DNA polymerase III comes along and begins to add complementary base pairs to nitrogen bases. • Works in 5’ to 3’ fashion… • Video Clip! DNA Replication Other Enzymes Involved: Ligase: Glues back sugar-phosphate backbone Topoisomerase: Regulates overwinding/ underwinding of DNA by cutting backbone http://highered.mcgrawhill.com/sites/9834092339/stu dent_view0/chapter14/dna_re plication.html Practice! • If one side of DNA reads CTCT, what would the complement side of DNA read? Write down on paper! GAGA! Then, The Cell Divides… • Mitosis: Makes 2 identical diploid (2 copies of chromosomes) cells from 1 parent cell: IPMAT