‘Introduction to Molecular Biology Learning Objectives (Chapter 6) Molecular Biology, DNA, chromosomes, and the central dogma. Understand Nucleic Acid Structure and properties (including alternate forms of DNA structure and superimposing, and remuneration) Explain the nature of Prokaryotic Chromosome Understand the differences in re-association kinetics of single-copy vs.. Repeated sequence Understand how DNA re-association provides a measure of genome size in base pairs Functions of DNA ERM Replication: genotypes function Expression: phenotypes function Mutation: evolutionary function
DNA Structure Base Pair Rules – Adenosine=Thymine, Guanine?Cytosine Charges rule: (Purina + Pyridine)A+C=T+G, ‘any cell of all organisms should have a 1:1 ratio of pyridine and Purina bases’ DNA is a double helix in a right handed manner. There is no relation between genome size and animal size. Central Dogma of Genetics: All DNA flows from DNA > Mrs. > protein Size: The helix has a NM diameter, and for each helical turn, there is -?10 nucleotides. Note that the smallest viruses are-?NM) It is named DNA because: D: Didgeridoo- The pentose sugar doesn’t have any oxygen on position 2. N: Nucleic- These molecules were first found in the nucleus of the cell (prior mitochondrial discovery), and in cytoplasm of prokaryote. A: Acid Two acid groups of phosphoric acid are used in forming DNA bonds. DNA consists of a long chain of nucleotides which consist of 1. Didgeridoos (a 5-carbon pentose) 2.
Phosphoric Acid 3. Nitrogenous Bases (nucleotides; either Pureness, or Pyridine’s) Each strand has opposite polarity (5′ 3′ and vice versa) Superimposing In vivo, DNA is naturally negatively supercilious (slightly unwound), when it’s ends are covalently Joined, DNA free end is wound in the opposite direction to the DNA helix Positively supercilious: overcrowd, also depends on handedness. Free end of DNA is wound in the same direction as the DNA helix Egg.
In a circular DNA molecule (such as a plasmid): If one/both DNA strands are cut then one end of the DNA is twisted while the other is held still, and the the DNA strands are re-joined, then the supercilious will be ‘locked in’ Supercilious require the ends tot the DNA molecules be fixed Exemplified in prokaryote, and eukaryotic chromosomes have attachment sites at intervals along the chromosome (and at the ends) to non DNA components of the horseshoe Over and underbidding of DNA occurs during replications and transcription and enzymes (such as topographies and gyrates) exist in cells to remove/add supercilious to allow these operations to proceed Topographies: begins initiation of Superimposing -DNA Gyrate: a topographies Chromosome Structure in Prokaryote In viruses and bacteria, all genes are contained in a single chromosome which can be either RNA/DNA. Detail? Eukaryotic DNA (refer to Module 9 for more detail) 20-50% of Eukaryotic genome contains repetitive DNA sequences (up to a million mimes) Two important groups of moderately repeated transposable elements 1. LINE: Long Interspersed Nuclear Element (-?EBPP, dispersed throughout genome) 2. SINE: Short Interspersed Nuclear Element (1 50-EBPP, -?500,000 copies dispersed throughout genome. Constitute 5% of genome) Denomination Melting (denaturing) DNA into single strands breaks apart the h-bonding. Re- annealing back to double-helix when the system cools down again. Rate of remuneration depends on; 1 . Concentration of solution DNA 2.
Complexity of DNA Remuneration Kinetics DNA in eukaryotic genomes is divided into 3 main classes . Unique single-copy DNA sequences (1-10 copies/haploid genome) – Most structural genes 2. Moderately repetitive DNA sequences (10-105 copies/haploid genome) – Structural genes for histories, RNA molecules and ribosomal proteins – All cells need lots of these molecules – Transposable Genetic Elements: can move from one location in a chromosome to another, and to different chromosomes 3. High repetitive DNA sequences (>105 copies/haploid genome) – Mostly located in heterocyclic regions of chromosome (egg. Centimeter and telemeter regions) – True function (if any) completely unknown