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DNA T & T
Translation and Transition
| Question | Answer |
|---|---|
| DNA Structure | -Deoxyribonucleic acid (DNA) is a very long molecule! -First isolated in 1868 by Johann Friedrich Miescher from pus cells of wounds. -Hereditary material of all living things |
| DNA Structure | -The molecule of hereditary is DNA. -50 years of research were needed to conclusively demonstrate that proteins WERE NOT hereditary molecules. |
| Griffiths, 1930’s | Used heat-killed virulent bacteria to transform live non-virulent bacteria. Concluded a“transforming principle”changed genotype |
| Avery, MacLeod, McCarty, 1940’s | Repeated Griffiths’ transformation experiment with isolated DNA and protein. Concluded transforming principle was DNA |
| Hershey & Chase, 1950 | Used virus which infects bacteria (bacteriophage) as experimental system. Radioactively labeled protein w/ 35S (no sulphur in DNA) and DNA w/ 32P (no phosphorus in protein structure) |
| Each nucleotide of the chains consists of | Deoxyribose A phosphate group A base (adenine, thymine, guanine, or cytosine) |
| Watson and Crick | Discovered that a DNA molecule consists of two polynucleotide chains twisted around each other into a right-handed double helix |
| Bonds in DNA Molecule | Phospho-diester bonds (covalent) hold backbone together. Hydrogen bonds hold nucleotide pairs together. |
| Complementary Base Pairing | Adenine (A) forms 2 hydrogen bonds with Thymine (T) Cytosine (C) forms 3 hydrogen bonds with Guanine (G). |
| Hereditary Molecule | The hereditary molecule must not only encode information to direct all cellular processes, but it must also be capable of identical replication. |
| DNA Polarity | The polarity of DNA is important structurally and functionally. 5’ = carbon of deoxyribose to which the phosphate group is attached. 3’ = carbon to which a hydroxyl group is attached. |
| Semi-conservative replication | Each “strand” of double helix serves as a template for the synthesis of a new strand. Polarity of each strand complicates replication |
| DNA Strand Replication | So the direction of replication is always in 5’ -> 3’ direction DNA Polymerase I requires a free 3’ –OH to extend the nucleotide chain. Initial piece of NT chain made by DNA Primase ( adds an RNA) |
| Leading Strand | Therefore the new DNA strand is synthesized as one continuous piece. The 5’ –> 3’ growing strand is called the leading strand. |
| Lagging Strand | Synthesis from the 5’-3’ template is a problem; DNA Pol I cannot extend from a 5’ end. Synthesis of the new strand occurs in pieces synthesized 5’ -> 3’. (Okazaki fragments). Multiple primers needed. |
| Overall Direction of Synthesis | The overall direction of synthesis of a new double helix is in the 5’ -> 3’ direction (polymerase) Once replication begins, the entire DNA molecule is replicated. |
| Nucleosomes | DNA double helix is associated with special proteins called histones. Four histone proteins form a “bead”, and DNA is wrapped around the beads |
Created by:
wayway
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