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23 Cards in this Set
- Front
- Back
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describe methylation and genomic imprinting as each relates to transcription
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methylation of cytosine; methylation of cis-elements decreases/silences gene transcription
genomic imprinting: gene expression is dependent on whether it is inherited from paternal or maternal chromosome. Either may be methylated and thus not expressed |
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what specific residues are acteylated to modulate gene transcription? what is the effect of acetylation on gene expression? who is responsible for each? which is associated with hetero/euchromatin?
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HAT (coactivator): actetylate Lys residues on histones (relaxes DNA and makes it more accessible to TFs); euchromatin
HDACs (corepressor): deacetylate Lys residues to restore positive charge; reduces gene expression; heterochromatin |
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describe the main ribozyme involved in mRNA splicing.
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U2 + U6 snRNA within spliceosome to catalyze splicing
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differentate the following as they relate to micro RNA
Dicer RISC SS miRNA |
Dicer: processes miRNA in cyto to produce DS miRNA duplex
RISC: cleavage and separation of RNA strands SS miRNA: binds to complementary sequence of mRNA to inhibit translation or stimulate degredation of mRNA |
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differentation transition and transversion DNA substitutions
differentiate Missense and nonsense mutations |
transition: within same class
transversion: purine to pyrimadine or vice versa missense: change in AA sequence nonsense: premature stop codon |
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Deamination by HNO2, depurination by alkylating agents, base analogs (bromouracil) and free radicals result in what kind of DNA mutation?
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base pair substitutions
transitions/transversions |
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Intercalating agents result in what kind of DNA mutation?
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insertions
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Depurination by alkylating agents and ionizing radiation result in what kind of serious DNA mutation?
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DNA strand breaks, deletions
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Bulky chemical groups (aromatic hydrocarbons) and THymine dimers (UV light) result in what kind of DNA mutation?
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distortion of double helix
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describe the fidelity of DNA replication:
DNAP Proofreading by DNAP DNA repair |
DNAP: 0.001
Proofreading: 0.01 DNA repair: 0.01 |
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How are the following repaired and what are the key components:
Alkylation of G at O6 DNA strand breaks base pair mismatch during replication damage of single base distortions/lesions of double helix gaps in DNA during replication DNA double strand breaks |
Alkylation of G at O6: direct reversal (o-mehtyltransferase, o-ethyltransferase)
DNA strand breaks: direct reversal (DNA ligase) base pair mismatch during replication: mismatch repair(hMSH2, hMLH2) damage of single base: base excision repair (DNA glycosylases, AP endonucleases) distortions/lesions of double helix: nucleotide excision repair (exinuclease complex) gaps in DNA during replication: Recombinatorial repair (Rad51, RuvA/B,C) DNA double strand breaks: Recombinatorial repair (Rad51, RuvA/B,C) |
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identify the defect in DNA repair mechanism for each of the following diseases:
HNPCC Xeroderma Pigmentosum Hereditary Breast Cancer |
HNPCC: mismatch repair (hMSH2)
XP: Nucleotide excision repair (exinuclease) Hereditary Breast Cancer: recombinatorial repair (BRCA1 and 2) |
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what is the inheritance of huntingtons disease?
tay-sachs? duchenne muscular dystrophy? Rett/Aicardi syndrome? alpha-1 antitrypsin deficiency PKU? |
huntingtons: autosomal dominant
tay-sachs: autosomal recessive duchenne muscular dystrophy: x-linkied recessive rett/aicardi: x-linked dominant alpha-1 antitrypsin deficiency: co-dominance PKU: autosommal recessive |
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define and differentiate the following:
pleiotropy penetrance variable expressivity heterogeneity |
pleiotropy: single genetic mutation produces diverse phenotypes
penetrance: probability a given genotype will express the phenotype variable expressivity: range of phenotypic manifestations of a given genotype heterogeneity: mutations in multiple unrelated genes cause the same/similar phenotype |
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what is pseduodominance as it relates to sick cell disease?
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psduodominance is a recessive condition that is present in two or more generations, thus appearing to be dominant
heterozygote advantage against malarial infection. high carrier frequency |
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what is the hardy-weinberg genotype formula and rule?
what are the 4 laws of HW equilibrium? |
p^2 + 2pq + q^2 =1; p + q =1
large populations random mating new mutation should be rare enough to ignore all genotypes should be equally fit to contribute to gene pool (reproduce) |
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what is Myotonic Dystrophy (DMPK1)?
describe the inheritance and hallmarks |
autosommal dominant; ANTICIPATION
severity depends on number of CTG repeats in 3' UTR 5-34: normal 35-49: premutation >50: penetrance 50-150: mild (onset 20-70yo) 100-1000: classic (10-30yo) >2000: congenital (birth to 10yo) |
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what are the ranges for Huntingtons disease? what is the triplet repeat and where is it?
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CAG repeat in protein coding region
autosommal dominant; ANTICIPATION normal: 10-26 premutation: 27-41 affected: 36-121 |
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what are the ranges for Fragile X syndrome?
what is the inheritance pattern? describe the difference between males and females: what is the term used to describe this special relationship describe the etiology of fragile X |
CGG repeat in 5' UTR
females less at risk; sherman paradox normal: <50 premutation: 50-230 mutation: >230 CGG are targets for methylation. methylation at 5' promoter region leads to a lack of transcription of the gene |
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what is imprinting and how does it lead to PW or Angelman sydrome?
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imprinting involves specific alleles on particular chromosomes, whose function is dependent on the parent from whom they originated. the result of imprinting is that there is only one functional allele for the imprinted gene
normally: on chromosome 15 the paternal UBE3A gene is methylated and the maternal SNRPN gene is methylated PWS: no SNRPN expression because maternal SNRPN is imprinted AS: no UBE3A expression because paternal UBE3A is imprinted 75%: deletion 23%: nondisjunction (UPD: uniparental disomy) 2%: imprinting error (extra stuff imprinted) |
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what are the three steps of X chromosome inactivation? what does the XIST gene do?
how is maternal or paternal x determined to be turned off? |
the XIST gene is the only gene expressed on the inactive chromosome; it initiatiates the process of inactivated
propogation of signal: changes the conformation of the inactive x chromsome because it is not actively transcribed-->barr body paternal or maternal x randomly chosen to be turned off |
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what is the term used to describe a situation in which normal and mutated mtDNA exist in the same cell..
describe and differentiate the two mitochondrial myopathies we have to know |
heteroplasmy
MELAS (mitochodrial encephalomyopathy, lactic acidosis and stroke-like episodes) MERRF (myoclonus epilepsy with ragged red fibers) |
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describe how to identify germline mosaicism in a pedigree. describe an example
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more than one child affected with an autosomal dominant disorder and parents are not affect; ex. Osteogenesis imperfecta type II
multiple cell lines in same individual |
