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29 Cards in this Set
- Front
- Back
Two formal terms used to describe categories of mutational nucleotide substitutions in DNA |
Transversions and transitions |
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An exonuclease enzyme breaks down nucleic acid molecules by Breaking the phosphodiester Bond at the 3 prime or 5 Prime Terminal nucleotides |
An endonuclease is required for the breaking of internal phosphodiester bonds |
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The XP phenotype is caused by defects in nucleotide excision repair pathways. Mutations in one of several genes can contribute to the XP phenotype. XP patients are extremely sensitive to UV radiation and sunlight. Cells form XP patients are deficient and unscheduled DNA synthesis. |
Xeroderma pigmentosum |
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These Concepts that affect gene mutations in diploid organisms would apply to haploid organisms such as E. coli |
Mutations are a source of genetic variation and provide the raw material for natural selection. Mutations have a wide range of effects on organisms depending on the type of base pair alteration, the location of the mutation within the chromosome, and the function of the affected Gene product. Mutations can occur spontaneously as a result of natural biological and chemical processes, or they can be induced by external factors, such as chemicals or radiation. Mutations comprise any change in the base pair sequence of DNA |
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Mutations that occur as a result of natural biological and/or chemical processes are considered what? |
Spontaneous mutations |
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Why are spontaneous mutations rare? |
They are relatively rare in comparison to induced mutations that are more directed to the physical or chemical properties of DNA. |
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Why is a random mutation more likely to be deleterious than beneficial? |
A functional sequence of nucleotides, Eugene, is likely to be the product of perhaps a billion or so years of evolution. Each gene and its product function in an environment that is also involved. A coordinated output of each gene product is required for Life. Deviations from the norm, caused by mutation, are likely to be disruptive because of the complex and interactive environment in which each gene product must function. However, on occasion a beneficial variation occurs |
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Why are most mutations in a diploid organism recessive? |
In most cases, the amount of product from one gene of each pair is sufficient for production of a normal phenotype. |
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What can change system to uracil and adenine to hypoxanthine by converting an amino group to a keto group? |
Deaminating agents |
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What will add a methyl or ethyl group to the amino Aikido groups of nucleotides, changing base pair of entities. |
Alkylating agents |
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What such as 5-bromouracil and 2-amino purine, are incorporated as thymine and adenine, but base pair with guanine and 16 respectively. |
Base analogs |
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A number of different types of mutation in the hbb gene can cause human B-thalassemia a disease characterized by various levels of anemia. Many of these mutations occur within introns or an upstream non-coding sequences. Why? |
Mutations and Upstream sequences May disrupt transcriptional factors and or eliminate binding Kama mutations and introns may affect RNA splicing, mutations in introns may affect mRNA stability or translation |
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What genetic defects result in the disorder xeroderma Pigmentosa in humans |
Defects in the DNA repair system |
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How did these defects in the DNA repair system create the phenotypes associated with xeroderma Pigmentosa |
By decreasing the rate of DNA mutation repair in skin cells |
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Are human made forms of radiation the major contributors to mutational load in humans |
Approximately 78% of the radiation exposure to humans comes from natural sources. Although diagnostic x-rays do contribute about 10% of the exposure, other forms of human made forms of radiation contribute only a relatively small amount. Human made radiation exposure is not a major factor |
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Identify the various types of DNA repair mechanisms known to counteract the effects of UV radiation |
Photo activation repair, excision repair, recombination or repair, SOS repair |
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What is dependent on Photo activated enzyme that Cleaves thymine dimers |
Photo activation repair |
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What is the process by which an endo nuclease Clips out uv-induced divers, DNA polymerase 3 fills in the Gap, and DNA ligase rejoins the phosphodiester backbone |
Excision repair |
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What uses the corresponding region of the undamaged parental strand of the same polarity |
Recombinational repair |
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What is a process in E.coli that induces error-prone DNA replication in an effort to fill gaps by inserting random nucleotides |
SOS repair |
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What is tautomeric shift |
Tautomeric shift is an intramolecular proton shift that changes the bonding structure of the molecule |
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Tautomeric shift may lead to a mutation. Why? |
It allows hydrogen bonding of normally non complementary bases |
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Variation in DNA sequences |
Allows for phenotypic variability, adaptation to environmental changes, evolution |
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Mutations are |
Source of new alleles, origin of genetic variation within populations, source of changes that lead to cell death genetic disease and cancer |
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Base analogs |
Compounds that can substitute for purines and pyrimidines, a compound that mimics the base, incorrect base pairings lead to mutations |
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Alkylating agents |
Donate alkyl group two amino or keto group two nucleotides, alter base pair of finity, transition mutations result |
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Intercalating agents |
Flat molecules that wedge between base pairs, cause distortions in base pair which can lead to DNA unwinding causing deletion or insertion |
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Damage reversal |
Damage type: modified bases, enzyme: multiple specific enzymes methyl guanine DNA methyltransferase, steps: enzyme binds to modified Bass, modification group is removed from base in DNA and covalently added to enzyme permanently inactivates enzymes result: revert to normal base without modification |
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Excision repair |
Damage type: damage base presence of uracil AP sites, enzymes: DNA glycosylase AP endonuclease DNA polymerase DNA ligase, steps: see slide, results: replacement of damaged base, uracil or repair of AP site |