DNA: History, Structure, & Function

DNA: History, Structure, & Function

Nucleic Acids • DNA (Deoxyribonucleic Acid) • A. Overview of Griffith’s 1928 Experiment • Two types of Streptococcus pneumoniae • a. rough (non-virulent) • b. smooth (virulent) • B. First experiment • 1. Rough serum • 2. Smooth serum

C. 2nd experiment 1. Rough serum heated 2. Smooth serum heated D. 3rd experiment 1. Live rough + heated smooth

2. Conjugation caused “transformation” • a. DNA = “transforming principle,” • changes what cells look like and do • b. Mendel’s “partikles” = genes = nucleic acids dead smooth Transformed from rough live rough

II. Structure of DNA • DNA – Deoxyribonucleic Acid • Composed of : • Phosphate, which is connected to a … • Sugar (Deoxyribose), which is connected to… • One of four nitrogenous bases • Adenine • Thymine • Guanine • Cytosine Complementary Bases Complementary Bases

II. Structure of DNA C. Nucleotide • One unit of phosphate, sugar, and base • One nucelotide base is connected to another, complementary one, by hydrogen bonds • This is called a “base pair” D. Codon • Group of 3 nucleotides in a row • Each codon codes for placement of one amino acid in a protein

II. Structure of DNA E. Genes • Group of codons on a chromosome that generally code for the production of a protein. • There are different kinds of genes • Promoters – Help other genes work better • Structural – Contain coding of proteins used outside • Regulatory – Turn others off and on (how many?) • Operational – Used in the cell to make “local” products F. Chromosomes • Long strands of DNA, each with many genes • One chromosome has +/- 20,000 genes on it. • A typical human cell has 46 chromosomes in it

II. Structure of DNA G. The Nucleus • Location in the cell in which most DNA is contained. • Some DNA is also found in the mitochondria, or energy making structures of the cell.

III. Function and Properties of DNA • DNA Replication • DNA can copy itself, using free-floating pieces of nucleic acid as building blocks • Occurs in mitosis and meiosis

III. Function and Properties of DNA B. Protein Synthesis Overview • Structural proteins are the big structural components of tissue (e.g. muscle, epithelial, etc.) • Enzymes are proteins that serve as catalysts, aiding chemical reactions in the body. • Amino acids are the building blocks of protein. • There are 20 important amino acids. • Proteins differ according to number of amino acids and the sequence in which they are arranged.

III. Function and Properties of DNA B. Protein Synthesis Overview, continued • Two basic steps to Protein Synthesis • Transcription (copying the message) • DNA partially unwinds • Free-floating RNAs “click in”, copying • Completed strand of mRNA breaks off • Translation (transporting and interpreting) • mRNA travels to ribosome • mRNA attracts tRNA with amino acids on them • amino acid chains form proteins • tRNA and mRNA return to their jobs

III. Function and Properties of DNA C. Understanding Protein Synthesis 1. DNA and RNA as a language Grammar Letters Words Sentences Paragraphs Example: THEFATCATATETHEREDRATENDTHEFATRATSATANDSATEND

III. Function and Properties of DNA C. Understanding Protein Synthesis 2. Protein Synthesis: a manufacturing business Crazy Industrialist in his “compound” Trusted Relative/Messenger The Factory The Factory Workers The Raw Materials The Finished Product

III. Function and Properties of DNA D. Mutation – a change in the genetic code 1. Point mutations – individual base changes a. Substitution b. Insertion or Deletion Examples: THEFATCATATETHEREDRATENDTHEFATRATSATANDSATEND THEFATCATATETHEREDBATENDTHEFATRATSATANDSATEND THEFATCATATETHEREDBRATENDTHEFATRATSATANDSATEND THEFATCATATETHEREDATENDTHEFATRATSATANDSATEND 2. Chromosomal mutation – major change a. Translocation

III. Function and Properties of DNA 3. Effects of mutation a. Nothing b. Slight change in gene product c. Change for the better or worse d. Lethal 4. Some causes of mutations: Radiation, chemicals, UV light, random error

DNA: History, Structure, & Function