Genetics 2313 Exam Chapter 8-13 Review Complete

BIO 2313 GENETICS EXAM 3 (CHAPTERS 8-13) REVIEW Chapter 8: DNA: The Chemical Nature of the Gene Chapter 9: DNA Replication and Recombination Chapter 10: From DNA to Proteins: Transcription and RNA Processing Chapter 11: From DNA to Proteins: Translation Chapter 12: Control of Gene Expression Chapter 13: Gene mutations, Transposable elements, and DNA repairs Chapter 8: DNA: The Chemical Nature of the Gene 8.1 Before knowing nucleic acids serve as the monomers of DNA, scientists concluded the genetic material must be able to: 1. Contain complex information - Instructions for the traits and functions of an organism 2. Undergo divisions and replicate or be replicated - To transmit genetic materials to the descendant cells 3. Encode the phenotype or have to the ability to code for traits - Genetic instructions are transcribed to RNA and translated into the amino acid sequence of a protein 4. Have the capacity to vary or mutate to generate diversity - For different genetic makeup 8.2 In the late 1800s, early scientists such as Miescher and Kossel studied the structure of chromatin and observed the four nitrogenous bases of DNA Scientist Levene believed DNA is made up of a series of linked monomers called nucleotides - Proposed each nucleotide has a sugar, a phosphate group and 4 nitrogenous bases (adenine, thymine, cytosine, guanine), AKA the tetranucleotide hypothesis ● Later confirmed INCORRECT Chargaff's rule states that DNA from any cell of any organism has a 1:1 ratio of pyrimidine and purine bases - Adenine and Thymine, Cytosine and Guanine would have the same percentage of composition - Remember: CUT THE PY (pie) and PURE AG (silver) Griffith (1928) performed experiments with several different strains of the bacterium Streptococcus pneumoniae - Some strains are virulent and cause pneumonia in humans and mice, and some strains are harmless Discovered that bacteria have the ability to transform harmless cells into virulent ones by transferring some genetic factors from one bacteria cell to another ● AKA the bacterial transformation or the transforming principle Avery, MacLeod, and McCarty (1944) published their classic findings that Griffith’s transformation factor is, in fact, DNA - Discovered an enzyme called DNase eliminated the biological activity of transforming substance - The research proved that DNA was the agent that carried the genetic characteristics from the virulent dead bacterial to the living nonvirulent bacteria ● Provided direct experimental evidence that DNA, not protein, was the genetic material Hershey and Chase (1952) carried out experiments that lent strong support to the theory that DNA is the genetic material - They tagged bacteriophages with the radioactive isotopes 32P and 35S - Since proteins contain sulfur but not phosphorus and DNA contains phosphorus but not sulfur, the radioactive 32P labeled the DNA of the phage viruses while 35S labeled the protein coat of the phage viruses ● Found when bacteria were infected with phage viruses, the radioactive phosphorus always entered the bacterium ● While the radioactive sulfur remained outside the cells ● Proved that DNA from the vial nucleus, not protein from the viral coat, was infecting bacteria and producing thousands of progeny Watson and Crick (1953) proposed the double helix structure of DNA - Showed that DNA consists of two nucleotide strands that run in the opposite direction, also known as anti-parallel - Two major pieces of information they used were the biochemical analysis (from Chargaff) and the X-ray diffraction analysis of DNA DNA can be described by the three levels of complexity Primary structure of DNA describes the nucleotide/linked nucleotides itself - DNA is made up of repeated subunits of nucleotides - Each nucleotide has a five-carbon sugar, a phosphate, and a nitrogenous base ● The name of the pentagon-sugar in DNA is called deoxyribose (different from ribose in RNA), hence the name deoxyribonucleic acid (DNA) ● Any of the four bases (adenine, guanine, cytosine, and thymine) can be found in a nucleotide - Uracil will be found only in RNA - In a nucleotide, the nitrogenous base is bonded to the 1’-carbon atom of the sugar - The term nucleoside is used to describe deoxyribose or a ribose sugar with a base, which is basically nucleotides without a phosphate group ● A phosphate group contains a phosphorus atom bonded to 4 oxygen atoms - Negatively charged, makes DNA acidic - Bonded to the 5’-carbon atom of the sugar - The DNA nucleotides are known as the deoxyribonucleotides, and the RNA nucleotides are known as ribonucleotides ● Ribonucleotides contain rarer modified bases - The nucleotides are linked together by a covalent bond between the 5’-phosphate group of one Carbon and 3’-hydroxyl group of the next Carbon - The nucleotides are also linked by phosphodiester bonds between the sugars and phosphates to form a polynucleotide strand ● AKA the sugar-phosphate backbone ● The same mechanism for RNA nucleotides - The polynucleotide strand has its own direction (or polarity) ● 5’ end refers to the end of the strand carrying a free phosphate group attached to the 5’-carbon atom ● 3’ end refers to the end of the strand carrying a free hydroxyl group attached to the 3’-carbon atom Secondary structure of DNA describes the stable, three-dimensional double helix structure of DNA - Consists of two nucleotide strands wound around each other ● Exterior sugar-phosphate linkage and bases are stacked in the interior of the molecule to stabilize the DNA structure - The two strands run in opposite directions