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Lesson 2.1 DNA, RNA, and Proteins ​ The Discovery of DNA Friedrich Miescher (1844–1895) isolated the material “nuclein” when studying pus cells from surgical bandages. -​ Deoxyribonucleic acid (DNA) -​ Ribonucleic acid (RNA) -​ ​ Role of DNA molecule -​ capaci...

Lesson 2.1 DNA, RNA, and Proteins ​ The Discovery of DNA Friedrich Miescher (1844–1895) isolated the material “nuclein” when studying pus cells from surgical bandages. -​ Deoxyribonucleic acid (DNA) -​ Ribonucleic acid (RNA) -​ ​ Role of DNA molecule -​ capacity to be replicated and inherited during reproduction of cell -​ provide avenues for mutation to enhance genetic diversity -​ primary genetic material in almost all living organisms -​ storage of genetic information A nucleoside is the complex of a sugar and ​ Structure of DNA a base. Four types are present in DNA. The subunits of nucleic acids are called nucleotides. Monomers of DNA The sugar in DNA is a deoxyribose. The nucleotides in DNA are named after the nitrogenous base they have. Thymine, Cytosine ,Adenine & Guanine ​ The Polynucleotide Chain The uniqueness of a polynucleotide chain of DNA is found on the sequence of the nitrogenous bases. By convention, it is The components of nucleotides are bound written in the 5’ to 3’ direction. by two types of chemical bonds. For example, 5'-ATGCTTGACTG-3’ or -​ glycosidic bond simply, ATGGCCTTAATGAG -​ phosphoester bond ​ Tautomers of Nitrogenous Bases The cyclic bases are classified to purines Remember; and pyrimidines. Cytosine: both RNA & DNA Thymine: DNA only -​ pyrimidines: single ringed bases Uracil: RNA only (cytosine,thymine and uracil) -​ Purines: double ringed bases (adenine and guanine)  ​ Tautomers of Nitrogenous Bases -​ The DNA structure is helical, similar The bases exist in alternative forms called to a twisted ladder tautomeric states. -​ Pyrimidines: amino and imino ​ DNA helix -​ Purines: keto and enol (Amino and keto tautomers are the physiologically important forms.) ​ The DNA Helix Two strands of DNA polynucleotide chains are bound together vía complementary base pairing. The two strands of DNA are said to be antiparallel. -​ One strand runs in 5′→3′ direction, while the other runs in 3′→5′ direction. -​ DNA is a double-stranded nucleic acid. The H bonds/ Hydrogen bonds of DNA molecule connect them Remember: PuAG stands for Purine, Adenine, and Guanine, while PyCT stands for Pyrimidine, Cytosine, and Thymine. Eukaryotic DNA Eukaryotic DNA is known to be: 1. linear or with distinct ends called telomeres 2. organized as chromatin (DNA + ​ The DNA Helix proteins) Rosalind Franklin (1920–1958) and her 3. packed through proteins called histones colleague Maurice Wilkins (1916–2004) into the following levels: performed x-ray crystallography techniques a. nucleosomes (beads-on-a-string model) to analyze the structure of DNA. b. 30-nm fibers of folded nucleosomes c. metaphase chromosomes (max ​ Chargaff’s Rules condensation) 1.​ The purine content is roughly equal to the pyrimidine content. 2.​ Adenine and thymine have equal quantities in DNA. 3.​ Guanine and cytosine have equal quantities in DNA. ​ Watson and Crick, with the aid of the works of Franklin, Wilkins, and Chargaff, postulated that: -​ The uniformity in size of DNA is due to the complementary base pairing. -​ The pairings involve specificity in H bond formation.  ​ The Amino Acids Amino acids are the subunits or monomers of proteins. Each amino acid consists of -​ a carboxyl group (COOH) -​ an amino group (NH2) Quaternary Structure -​ a proton This level is attained whenever multiple -​ a varying R group folded protein subunits form a single complex to confer greater functionality. ​ Levels of Protein Structure Amino acids are organized into polypeptides and proteins via different levels. -​ Primary structure -​ Secondary structure Remember: -​ Tertiary structure The levels of structures of proteins can -​ Quaternary structure easily be distinguished by the prevailing bonds that hold and maintain them. Primary Structure Peptide bonds hold the substituent -This level is attained by the formation of a amino acids together. peptide bond between each of the amino Hydrogen bonds form helices and acids. sheets. -Peptide bond is a covalent linkage between Tertiary structures are stabilized by amino acids. covalent and weak non-covalent interactions. Quaternary structures require more complex molecular interactions between large protein subunits. Deoxyribonucleic acid or DNA is the primary genetic material in living organisms Alongside ribonucleic acid or RNA, it is classified as a nucleic acid. Secondary Structure Secondary protein structures may be in the The basic subunit of nucleic acids is the form of a helix or a pleated sheet. nucleotide. ○ Each nucleotide consists of three basic components—a 5-C sugar, a phosphate group, and a nitrogenous base. In DNA, the nitrogenous base may either be adenine, guanine, thymine, or cytosine. -sugar in DNA is deoxyribose RNA, on the other hand, has uracil in place of thymine. -sugar in RNA is ribose ​ Prokaryotic DNA, which is characterized as circular (or covalently closed), is organized into domains in the nucleoid region. Tertiary structure Eukaryotic DNA, on the other hand, consists of polypeptides and both helices is organized into nucleosomes, and sheets 30-nm chromatin fiber, and eventually, the metaphase chromosomes.