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MCB Block-4 Gems 2
AUC
18
Microbiology
Graduate
04/05/2011

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Cards

Term
Genetic Anticipation
Definition
Disease severity increases or age of onset decreases from one generation to the next
Term
Classification of alleles in tandem repeat expansions
Definition
Mutable: Do not cause disease but show meiotic instability(Sex specific)

Slipping back, expand.(looping out of okazaki fragments.)

Slipping forward(looping out of template strand = Contraction.

Intra-strand hairpins is the key to dynamic instability
Term
Repeat Disorders

Fragile X:
Freidreich Ataxia:
Huntington, SCA:
Freidrecih Ataxia:
Myotonic Dystrophy:
Definition
Fragile X: CGG 5'utr, Maternal.

Huntington, SCA: CAG coding paternal

Freidreich Ataxia: GAA Intron

Myotnic Dystrophy: CTG(I)Coding
or CCTG(II) Intron
maternal
Term
Dna testing for Dynamic Mutations
Definition
(NNN) 6-200 PCR
(NNN) > 200 southern blot
Term
Cytogenetic diagnosis of Fragil X
Definition
Non staining constriction near the distal end of Q

Heavy amount of methylation on repeat expansion causes lack of staining.

Probe 5' region of FMR1 gene.

CGG repeats methylated. MeCP2 binds, recruits HDACs. Chromatin condensation
Term
FRAXAS and Fredreich Ataxia
Definition
Mutation may be due to triplet expansion or missense mutation/deletion.

Both diseases are null mutation.

Associated tremors in FRAXAS(late in life) are due to altered RNA function.
Term
Pathogenetic Mechanism of CTG repeats in DM1 and DM2
Definition
DM1 and DM2 mRNA is CUG. CUG repeats titrate out an RNA binding protein necessary for correct splicing of other mRNAs.
Term
Pathogenesis of polyglutamine diseases
Definition
Huntingtons and SCA.

Insoluble aggregates or inclusions from protein.

Inclusions are protective.

Selective pathogenesis of htt.

Rhes is only expressed in Cerebral cortex.

Rhes binds mHTT and promotes sumolyation.

Aggregate -> soluble by SUMO. Solubule is cytotoxic.
Term
Male and Female differentiation
Definition
SRY -> SOX9 SOX9 inhibits female WNT4.

WNT4 -> DAX1 inhibits SOX9
Term
XIST
Definition
Acts as mRNA. Only enough for 1 x chromosome is produced.
Term
Huntington and SCA diagnosis
Definition
PCR
Term
Pathogensis polyglutamine diseases
Definition
• Pathogenesis of polyglutamine diseases is not through the cellular inclusion formation but through interference with transcriptional regulation of key cell cycle regulator genes
Term
Haploinsufficiency
Definition
Loss of function. Half is not enough

Generally, all(different) mutations in a gene result in same phenotype.

Nail Patella Syndrome
Term
Gain of function.

Autosomal Dominant mechanism
Definition
Up-regulation, novel function.

Normally Missense

Different mutations in same gene may

Null gives opposite disease.

FGFR3
Term
Dominant Negative
Definition
Mutant protein interferes with normal protein (collagenopathies)

Different mutations in same gene -> same phenotype

Null gives milder disease
Term
OI type 1 vs Type 2-4
Definition
Type 1: Null mutations, haploinsufficiency

Type 2-4: missense, dominant negative
Term
Premature termination codon
Definition
End result is no protein made.

Null mutation
Term
Disorders due to gross changes in DNA.
Definition
usually recombination between non-homologous repeat sequences

22q11 deletion syndrome
a-thalassaemia
Williams-Beuren Syndrome
Smith-Magenis

Deletion usually worse then duplication
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