12642022
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 |
| Name 4 types of mutations | (i) Single base pair changes (ii) Transition mutations (iii) Transversion mutations (iv) Spontaneous mutations |
| What are transition mutations? | Purine for purine (AG) Pyrimidine for pyrimidine (TCU) |
| What are transition mutations? | Pyrimidine for purine and vice versa |
| Name 5 causes for spontaneous substitutions | 1. Mis-pairing DNA during replication. 2. Tauntomerisation. 3. Anomalous base-pairing (non Watson-Crick). 4. Quantum tunneling. 5. Depurination. |
| What is depurination? | Loss of a purine base from a nucleotide leading to an abasic site - a gap. No info to say what base should be paired to it Leads to permanent spontaneous mutation |
| How to get uracil from deamination | -NH2 cytosine |
| Thymine | 5-methylcytosine |
| What do these deamination events generate? | Mismatch pair e.g. A-G. |
| What sort of mutations are common in species with heavily methylated cytosine? | CG --> AT transitions. |
| Name 2 examples of chemical mutagens | Alkylating agents Nitrous acid (HNO2) |
| Name an example of an alkylating agent and its effect. (4) | Ethyl Methyl Sulphonate (EMS) Ethylates G DNA pol tends to add T to this Leads to transition mutations. |
| What are base analogues? Name an example. | Compounds that look like bases and may be incorporated. 5-Bromouracil Keto form resembles Thymine Enol form resembles T' |
| What are the forms of 5-bromouracil and what do they resemble? | Keto form - thymine Enol form - 'T which can BP w/ guanine |
| What does this cause? | TRANSITION MUTATION COMPLEMENTARY STRAND |
| Name 3 different types of mutations that affect protein function | Silent Missense Nonsense |
| What's the effect of a silent mutation? | Changes codon to another codon Encodes the same amino acid. |
| What's the effect of a missense mutation? | Changes codon encodes a different amino acid altering amino acid sequence |
| What's the effect of a Nonsense mutation? | Changes codon to a stop codon causes protein truncation. |
| What are the potential consequence of single base pair changes? | LOF of gene GOF of gene No effect on gene activity |
| Why is it unlikely for a SBP change to be serious? | Only ~1% of the human genome is protein coding |
| Why isn't this true for E.Coli? | As only ~12% of the genome is non-protein coding. |
| What can cause INDELs? | Replication slippage in replicating DNA |
| What do DNA intercalating agents cause? | Insertions Frameshift mutations |
| What are DNA intercalating agents? | Base-analogues that wedge into the DNA heilx |
| Name an example of a DNA intercalating agent | Ethidium Bromide an intercalated dye |
| What is replication slippage? | Loss/gain of base(s) occurring commonly in long stretches of the same base. |
| What is Huntington's caused by? | CAG (Glutamate) repeats If >40 repeats occur by FW/BW slippage If the looped out repeat is annealed then the repeat expands during replciation. |
| What are the effects of small INDELs within the coding strand? (3) | Leads to frameshift Multiples of 3 don't cause frameshift, do alter protein. Can cause triplet expansion diseases like Huntington's. |
| What are the effects of small INDELs outside of a coding strand? | Effect often silent, although can alter gene regulator function. |
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