6085865
Description
Flashcards by Emma Allde, updated more than 1 year ago
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Created by Emma Allde
over 7 years ago
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| Question | Answer |
| What are the 3 forms of induced mutation and what are their main mechanisms of action | Physical (ionising radiation) ( single or double strand breaks), UV light (causes thymine dimers) and chemical (agents that react with nuclear bases) |
| What is UV-C (180-290 nm) | Light found in daylight as it is absorbed by the ozone layer; the most energetic and lethal |
| What is UV-B (290-320 nm) | The major mutagenic fraction of sunlight |
| What is damage causes by UV irradiation | chemical bonds between adjacent thymines distorting DNA and causing problems during DNA replication, often resulting in point mutations |
| What is Nitrous acid an example of | Chemical agent that results in (CG > TA) point mutation |
| What is Alkylating agents an example of | Chemical agent that results in guanine modification, GC > AT |
| What are Free radicals examples of (strand breaks and base modification) | Chemical agent |
| What are free radicals | ○ Unstable, highly-reactive molecules created during normal metabolism and in response to environmental factors ○ May play a role in the development of cancer, cardiovascular disease, and other diseases of aging by reacting with and damaging DNA and other parts of cells. |
| What is Xeroderma pigmentosum (XP) | a mutation that results in defects in a single strand nucleotide excision repair (NER) gene (XP-D), which prevents repair of thymidine dimers as it encodes for helicase required for NER |
| What are the symptoms of Xeroderma pigmentosum (XP) | Dry skin w/ melanoma and other cancers by about 1000x ("children of the night") |
| What are the general characteristics of cancer cells | Do not grow old and die No reproductive limit |
| How many mutations are sufficient to turn healthy somatic cell to a cancerous cell To the point where DNA polymerase will not recognise mutated strand | 5-6 mutations |
| How many (%) of human primary tumours test positive for telomerase activity | 85% |
| What kind of point mutations are there (4) | • Silent (synonymous) • Missense (non-synonymous) • Nonsense • Indels |
| What is a silent mutation | a single point mutation that doesn't change the coded amino acid e.g. CGA (Arg) -> CGG (Arg) |
| What is a missense (non-synonymous) | a single point mutation that DOES change the coded amino acid e.g. Sickle cell anaemia (GAG (Glu) > GTG (Val)) N-Ras (CAA (Gln) > CAC (His)) |
| What is a nonsense mutation | a single point mutation that does not coded for an amino acid e.g. a STOP or START codon instead where there shouldn't be one TGC (amino acid codon) > TGA (stop codon) resulting in trunkated polypeptides |
| What are indels (mutations) | small scale insertions and deletions |
| What kind of indels exist (2) | Insertions/deletions with multiple of 3 that maintain of reading frame Insertions/deletions NOT with multiple of 3 |
| loss of 508th codon in CFTR > cystic fibrosis when homozygous is an example of what kind of mutation | Insertions/deletions with multiple of 3 that maintain of reading frame |
| Which mutation results in frame shifts resulting in non-native polypeptides which can be catastrophic | Insertions/deletions NOT with multiple of 3 |
| What is Huntington's disease an example of | Serious consequences of small scale insertion/deletion namely: Trinucleotide CAG (glutamine) repeat on huntingtin gene (from 10-34) to (36-121) > neuronal decay |
| What happens as a result of loss of 32bp in CCR5 | Individuals homozygous for change in 32 CCR5 allele are resistant to HIV-1 |
| What is CCR5 | The binding receptor HIV goes for on macrophage |
| What is cri du chat | A chromosomal deletion in chromosome 5p that results in children who are mentally retarded, have small heads, and have a cry that sounds like a loud cat The children die at a young age |
| What is Chronic myelogenous leukaemia (CML) | A genetic disease due to translocation where a portion of chromosome 22 gets swapped with a piece of chromosome 9 resulting in a Philadelphia Chromosome Its a cancer affecting white blood cells |
| What are the 3 examples of spontaneous mutation | - errors in DNA replication which escape proofreading and repair mechanisms - replication slippage - deamination |
| What is replication slippage | Gain of repeats - reverse slippage Loss of repeats - forward slippage |
| What is deamination | ○ The removal of an amino group from an organism, particularly from an amino acid ○ C will then pair with A and A will then pair with C, e.g. |
| What causes human immunodeficiency virus (HIV) | an enveloped RNA retrovirus infects CD4 T cells and uses the enzyme reverse transcriptase to mediate synthesis of proviral DNA which integrates into the host cell genome |
| What do CD4 T cells do | Recognises and binds to MHC II antigens and helps stabilise the binding of antigenic determinants to T cell receptor |
| What do the high mutations rate of HIV genome result in | drug resistant viruses |
| What do early HIV symptoms resemble | Influenza: Fever Chills Rash Night sweats Muscle aches Sore throat Fatigue Swollen lymph nodes Mouth ulcers |
| What does Azidothymidine (AZT) do | Inhibits multiplication of HIV and other retroviruses by blocking reverse transcription and production of virally encoded DNA |
| What is the main issue with Azidothymidine (AZT) | Eventually patients stopped responding to treatment |
| What is the HIV mutation rate | 10^-3 per base One of the highest of any virus (or anything else) observed to date 1 x 10^6 faster than human genome |
| What is the typical mutation rate of a eukaryotic genome | 10^-9 per base |
| What is reverse transcriptase | An DNA polymerase enzyme encoded by some certain viruses (retroviruses) that uses RNA as a template for DNA synthesis |
| What features of reverse transcriptase make it so lethal (2) | • More error prone their other nucleic acid polymerases • Does not possess an exonuclease 3' to 5' so does not have any proofreading capacity |
| What is Acute myeloid leukaemia | • A cancer of the blood in which a person produces faulty white blood cells • Immature white blood cells are overproduced and they crowd the bone marrow and cause it not to make normal blood cells |
| What do all forms of AML have in common | the same 9 mutations |
| Which genes are mutated in AML (3) | oncogenes, tumour suppressors and novel genes |
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