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Description
Flashcards by J yadonknow, updated more than 1 year ago
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Created by J yadonknow
over 6 years ago
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| Question | Answer |
| What are the 3 conformations of DNA and their structures? (6) | B-DNA: Most DNA is B-DNA A-DNA: 16 bp/turn Forms when DNA is dehydrated Z-DNA: 12 bp/turn, left-handed zig-zag, may form if DNA contains long runs of GC alerations. |
| How does supercoiling occur? | Supercoiling occurs when DNA is under/overwound and twists around itself. Undewinding generates negative supercoiling. Overwinding generates positive supercoiling. |
| What sort of supercoiling arises in unwound DNA with fixed ends? | Positive supercoiling. |
| How is most DNA supercoiled? | Negatively. |
| Explain the process of denaturation of a DNA molecule. | When heated at 70c-110c or exposed to alkaline conditions, denaturation occurs. If allowed to cool slowly the DNA strands will re-anneal as H bonds reform between base-pairs. |
| How is denaturation monitored? | By measuring absorbance of UV light at 260nm Single stranded DNA absorbs more UV light than double stranded DNA, therefore absorance rises as DNA denatures - This is seen as a hypochromic shift (shorter Wavelength). |
| What does Melting Temperature(Tm) mean? | The temperature needed to denature 50% of DNA molecules or 50% of base pairs in the strands of a sample. |
| What factors increase the Melting Temperature? | An increase in G-C base pairing, (more GC=More hydrogen bonding= more energy required to denature molecule.) Presence of cations e.g. Na+ which reduce repulsion between negatively charged phosphate groups on the 2 strands. |
| How does an RNA nucleotide differ from a DNA nucleotide? | Has an addition OH group on C2, which makes RNA denser and more reactive than DNA. Uracil is used in place of Thymine, which is structurally similar to uracil differing by 1 extra methyl group. |
| State the nomenclature of the ribosomal nucleotides | Adenosine Monophosphate (AMP) Guanosine Monophospate (GMP) Cytidine Monophosphate (CMP) Uridine Monophosphate (UMP) |
| What does double stranded RNA resemble? | The A comformation of DNA |
| How does RNA's structure relate to its function(s)? | RNA molecules have greater flexibility than DNA and may fold in on themselves to form complex 2' structures i.e. tRNA |
| What are the three different forms and functions of RNA? | tRNA - Transport mRNA - Carry info rRNA - act structurally or catalytically |
| What is a gene? | An entire stretch of DNA necessary for the production of a particular functional product, which may be a protein or an RNA molecule. Genes determine the characteristics of an organism. |
| What is the genome? | The genetic material contained in an organism, cell, virus or organelle. |
| What is a chromosome? | A single long molecule of DNA that includes numerous genes, the DNA of a chromosome is usually associated with proteins. |
| What is Chromatin? | The DNA-Protein complex present in the nuclei of Eukaryotic cells during interphase. |
| How do we know that genes are made of DNA? | As alterations of DNA cause genetic diseases Introduction of foreign DNA into an organism may alter its characteristics. |
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