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L311 Genetics T2
Forrester Test 2 Study cards
| Question | Answer |
|---|---|
| epigenetics | heritable state of gene function not encoded within DNA sequence |
| examples of epigenetics | cell differentiation (example: muscle cell) |
| genomic imprinting | expression of trait depends on whether mutant from mom or dad |
| example of genomic imprinting | Prader-Willi: (paternal) mild mental retardation |
| position effect variegation | position of gene on chromosome affects its expression |
| X chromosome inactivation | one of two X chromosomes is inactivated by RNA interacting with DNA |
| prion (not a virus) examples | transmitted via altered protein 1. Creutzfeldt-Jakob disease: progressive neurodegeneration 2. scrapie: neurodegeneration and death 3. mad cow disease: scrapie transmitted to cows 4. vCJD (varian Creutzfeldt-Jakob disease): through consumption of infe |
| forward mutation | change from wt to mutant |
| reverse mutation | change from mutant to wt |
| mutation | the molecular change |
| types of mutations | 1. base pair substitutions (DNA level and protein level) 2. frameshift |
| transition | is a base-pair substitution at DNA level -replaces pyrimidine with the other |
| transversion | is a base-pair substitution at DNA level -replaces pyrimidine with purine |
| silent mutation | base-pair substitution at protein level -triplet encodes same amino acid |
| synonomous mutation | same as silent |
| missense mutation | codon specifies different amino acid |
| nonsense mutation | codon specifies stop codon |
| frameshift mutation | different from base-pair substitution! nucleotide additions or deletion that change the reading frame. often introduce stop shortly downstream. |
| somatic mutation in dividing cells | gives rise to clone of cells with mutation |
| recessive somatic mutation | no phenotype if diploid |
| dominant somatic mutation | mutant phenotype expressed |
| germ line mutation | may be passed to offspring |
| loss-of-function mutation | no gene function |
| gain-of-function | gene product has new function |
| adaptive mutations | permit growth under selective conditions |
| sources of spontaneous mutations | 1. errors in replication 2. spontaneous lesions 3. transposons |
| depurination | spontaneous lesion -spontaneous loss of purine base |
| deamination | spontaneous lesion loss of amine from cytosine produces G-C to A-T transition |
| oxidative damage | consequence of aerobic metabolism and radiation. An example of a spontaneous lesion |
| transposons | DNA sequence that can move to new locations |
| human diseases caused by spontaneous mutations (expansion of repeats) | fragile X syndrome: results from expansion of CGG in 5' UTR |
| trinucleotide repeat examples | Kennedy disease: progressive muscular atrophy myotonic dystrophy: most common muscular dystrophy Huntington's disease: neurodegeneration |
| Genetic Effect | Genetic makeup in individual affects expression of traits |
| Environmental Physical Effect | External physical effects can affect expression of traits |
| Genetic Suppression | Nonsense mutation for Trp synthesis. Suppression tRNA restores growth without adding Trp. (need a better description) |
| Position affect | The location of a dominant gene affects its expression (eg: translocation of dominant gene to heterochromatin will stop its expression ) |
| Age Onset | Expression of phenotype is dependant on age of individual (eg: Huntington's Chorea) |
| Sex Limited | Traits are only expressed in one gender (eg: horns are only present on male sheep) |
| Sex Influenced | Traits are expressed in both |
| Genetic Anticipation | appearance of symptoms of inherited disorders earlier with the succession of generations (from generation to generation |
| Conditional Mutations | cause phenotypes under restrictive conditions but are not detectable under permissive conditions. Rare mutations |
| Temperature Sensitive Mutation | Type of conditional mutation Defect seen only at restrictive temperatures. eg: Himalayan Rabbits which have color enzymes that only function at cooler temperatures |
| Nutritional effect | Type of conditional mutation. Loss of enzyme that codes for AA can prevent growth if AA is not present in diet eg: trp- yeast not growing in environments without trp |
| Linked Genes | genes located on the same chromosome that tend to be inherited together in genetic crosses |
| Recombination | Exchange of genetic material from maternal and paternal chromosomes during crossing-over. |
| Crossing Over | Exchange of corresponding chromosomes segments between homologs |
| Parental genotype | Genotype of offspring same as the the parents (most common) |
| 3 Factor Cross | Can be used to determine gene order and distance Double crossovers switches the middle gene relative to others Strategy: 1. Cross 2 true breeding parents to create triple het 2. cross triple het X homo recessive 3.Observe F2 Phenotypes 4. Look for p |
| Independent Assortment | the random distribution of the pairs of genes on different chromosomes to the gametes. Unlinked genes |
| Genetic Map | Linear representation of gene arrangement on the chromosome |
| Map Unit | Unit of genetic distance measured in centimorgans |
| Mitotic Recombination | crossing over that occurs during mitosis |
| Mitotic Nondisjunction | Abnormal nondisjunction occur after fertilization in one of the somatic cells |
| Mitotic Chromosome Loss | Patch of tissue may arise from a cell that looses a chromosome during cell division |
| Twin Spot | both recessive phenotypes expressed side by side |
| kinetochore | centromere plus associated proteins |
| holocentric | type of centromere; spindle attaches along length of chromosome |
| localized centromere | spindle attachment localized |
| metacentric | submetacentric |
| telomere solving the problem | composed of many tandem repeats of short sequences; telomerase enzyme adds DNA to telomeres |
| base analogs | chemicals similar to bases; can be incorporated by DNA pol. into DNA during replication and cause mispairing |
| 5-bromouracil | base analog |
| 2-aminopurine | base analog |
| EMS | an alkylating agent that alters base so that it can pair with incorrect partner. Specifically |
| intercalators | chemicals that insert themselves into DNA |
| UV light | causes DNA damage |
| ionizing radiation | causes wide range of DNA damage because the radiation interacts with compounds in solution to produce highly reactive free radicals |
| examples of ionizing radiation | alpha and beta particles |
| lesions produced by ionizing radiation | 1. single strand breaks 2. double strand breaks 3. alterations of nucleotide bases |
| DNA repair mechanisms (6) | 1. prevention of errors 2. direct reversal of damage 3. excision repair 4. mismatch repair 5. error-prone (SOS response) 6. recombinational repair |
| prevention of error | some enzymes remove/inactivate mutagen (example superoxide dismutase eliminates oxygen free radicals) |
| photolyase | direct reversal of damage -breaks extra bonds formed in pyrimidine dimers |
| alkyltransferases | removes alkyl groups such as O-6 ethyl guanine |
| general excision repair | error is cut out and replaced |
| specific excision repair | DNA glycosylases cut base-sugar bonds removing altered base |
| mismatch repair | occurs shortly after replicaiton |
| error-prone (SOS response) | emergency repair |
| recombinational repair | uses homologous DNA to repair damaged DNA |
| diseases caused by repair defects | 1. xeroderma pigmentosum 2. heriditary nonpolyposis colorectal cancer |
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