General Interview Questions - Nucleic Acids & Genes

How is information stored in nucleic acids? how is this information used by cells and viruses?

What is meant (scientifically) by the terms replication, transcription and translation?
Explain why RNA can (sometimes) be catalytic whereas DNA is not. How do these two related molecules differ?
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1. All organism store genetic information in molecules of double-stranded deoxyribonucleic acid (DNA).
2.Some viruses use single stranded DNA, single- or double-stranded ribonucleic acid (RNA) rather than double-stranded DNA to store genetic information.
3. DNA differs from RNA in that the hydroxyl group on the C2 carbon of ribose is replaced by a -H. Instead of uracil (in RNA), DNA contain thymine.
4. In both DNA and RNA, information is stored in the sequence of the nucleotides along the length of the molecule.
5. Each strand of a DNA double helix is a polynucleotide molecule, composed of deoxynucleotide subunits.
6. A deoxyribonucleotide consists of a phosphate group, attached to the 5’ carbon of the sugar deoxyribose. One of four nitrogenous ‘bases’, either a purine (cytosine or thymine) or a pyrimidine (guanine or adenine), is attached to the 1’ carbon of the sugar. In a ribonucleotide, the sugar ribose is used and the purine uracil is used instead of thymine are used)
7. The chains in a double stranded DNA molecule are anti-parallel and complementary. If there is an adenine residue on one chain, there is a thymine residue on the other. Similarly, if there is a cytosine on one chain, the other chain contains a guanine residue.
8.These base pairs interact through hydrogen bonds, three between C and G, two between A and T.
9. Both DNA and RNA are synthesized using nucleotide triphosphates. These are added the 3’ OH group of the sugar (deoxyribose or ribose), creating a phosphodiester bond and releasing pyrophosphate
10. The enzymes that mediate DNA synthesis require a pre-existing nucleic acid primer to add on to.
11. Both DNA and most RNA polymerases use a nucleic acid template to determine the sequence of nucleotides in the newly synthesized molecule. An exception, polyA polymerase, mediates the addition of AAA(n) to mRNAs.
12. During DNA replication and RNA transcription, the two strands of a double-stranded DNA molecule must separated so that they can be used as the templates for the synthesis of a new nucleic acid strand. Replication uses both strands, transcription one.
13. DNA is used only to store information, RNA can both store information and perform structural/catalytic functions.
14. The information stored in DNA is used in two distinct ways. First, sequences along the DNA are recognized by regulatory factors, mostly proteins, that bind to specific nucleotide sequences and determine which regions of the DNA are transcribed into RNA. Second, sequences of DNA are transcribed into RNA.
15.A gene can be defined as the region of DNA that contains the sequences transcribed to produce the gene product and regulatory sequences that control transcription.
16. Changes in the nucleotide sequence of a gene can change when, where, how much and the type of gene product produced.

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