MCB 3rd Unit 3 Flashcards
What is the inheritance pattern of most hemoglobinopathies?
AR
The two broad categories of hemoglobinopathies are:
Structural variants and thalissemias
Thalissemias are an imbalance in relative amounts of:
Alpha and beta chains
Carriers of Hb beta are statistically likely to be:
Italian/Greek
Carriers of HbS are statistically likely to be:
African
What type of hemoglobin is fetally expressed?
HbF
What type of hemoglobin is expressed in adults?
HbA
E6V mutation in hemoglobin results in what disease?
Sickle Cell (HbS)
The E6V mutation in sickle cell causes an abnormal interaction between ___ chains including hydrophobic interactions, polymerization of HbS globin chains, and sickling
Beta globin
The E6K mutation in Hb gene leads to:
HbC
Compensatory hyperplasia of bone marrow is a feature of:
Alpha thalissemia
An inclusion of denatured hemoglobin is called a:
Heinz body
Teardrop cells common in beta-thalissemia after spleen removal are called:
Dacrocytes
Clinical severity of alpha thalissemia correlates with:
Number of genes deleted (2 copies each of HBA1 and HBA2)
The most severe form of alpha thalissemia, in which no alpha globin is expressed is:
Hydrops fatalis (lethal in utero, 4 genes deleted)
If only one alpha hemoglobin gene is present, the resulting disease is:
HbH disease
B+ Thalissemia, better known as ___, results in reduced expression of beta globin and milder anemia than B0 Thalissemia
Beta Thalissemis Intermedia
Alpha thalissemia involves complete gene deletions, what is the cause of beta thalissemia?
Null mutations (typically point mutations)
What is Hereditary Persistence of Fetal Hemoglobin (HPFH)?
When lambda globin expression persists in adulthood due todeletions of beta and gamma globin
Alpha globin is a ___ for beta-thalissemia
Modifier gene
What type of mutations are stably transmitted to offspring and retained in somatic tissues?
Static
What type of mutations may continue to mutate during transmission to offspring and tissue development?
Dynamic
What is a common feature to all dynamic mutation disorders?
Neurological symptoms, most are trinucleotide repeat disorders
Backwards slippage in a trinucleotide repeat causes:
Expansions
Forward slippage in a trinucleotide repeat causes:
Contractions
“Anticipation” was originally known as the:
Sherman Paradox
Non-Transmitting Males (NTM’s) are explained by:
Mutable (premutation) alleles
Most trinucleotide repeat disorders show which heritability pattern?
Dominant
The repeat sequence seen in Freidrich’s ataxia is:
GAA
The repeat sequence seen infragile X is:
CGG
The repeat sequence seen in Huntington’s disease (and SCA) is:
CAG
The repeat sequence seen in myotonic dystrophy is:
CTG
CAG expansions (Poly-glutamine) express a ___ expansion bias
Paternal
CGG, CTG, and GAA expansions express a ____ expansion bias
Maternal
Fragile X expresses a ____ expansion bias
maternal
Huntington’s disease expresses a ____ expansion bias
paternal
Myotonic dystrophy expresses a ____ expansion bias
Maternal
Cerebellar ataxia expresses a ____ expansion bias
Paternal
Freidrich ataxia expresses a ____ expansion bias
Maternal
The gene associated with fragile X is:
FRAXA
The gene associated with myotonic dystrophy is:
DM1
The gene associated with Freidrich ataxia is:
FRDA
The mode of inheritance for Fragile X is:
XD
What are three ways to measure repeat expansions?
PCR/gel electrophoresis
Southern blot
Western blot (not routine)
The mode of inheritance for myotonic dystrophy is:
AD
The mode of inheritance for Huntington’s disease is:
AD
The mode of inheritance for Spinocerebellar ataxia is:
AD
The mode of inheritance for Friedreich’s ataxia is:
Autosomal recessive
Freidreich’s ataxia is caused by GAA expansions in intron 1 of:
Frataxin (FXN)
Is there anticipation in FRXA? Is it associated with the small or large allele repeat?
No, small
FRXA results in excess ___ accumulation in mitochondria, leading to energy deficiency and free radicals
Iron
What is the 2nd leading cause of inherited mental retardation?
Fragile X Syndrome
Fragile X is caused by ___ expansions in the 5’ UTR of the ___ gene
CGG, FMR1
Symptoms of fragile X include:
MR, autism spectrum
Delayed milestones
long face, large ears, prominent forehead/jaw
Macroorchidism
Epigenetic silencing involves binding of MeCP2, which recruits corepressor complex:
Sin3 with HDAC’s
What type of protein is FMRP?
RNA binding protein (limits translation)
FXTAS involves ___ onset neurodegeneration, increase FMR1 mRNA in the brain but reduced translation, mRNA toxicity, gain of function at RNA level
late
Myotonic dystrophy is an AD disease involving CTG expansion in the 3’ UTR of the ___ gene
DMPK
Does muscular dystrophy undergo anticipation?
Yes
Symptoms of DM1 include ptosis and an open, ___ mouth
Triangular
DM1 involves a decrease in ___ protein and an increase in ___ protein
MBNI, CUGBP1
DM1 involves pleiotropy due to abberant missplicing of multiple genes, causing a ____ effect
Trans-dominant
What disease includes progressive loss of motor function, onset 30’s-40’s, depression, and chorea
Huntington’s Disease
What disease includes slowly progressive cerebellar degeneration, late onset, and ataxia
Spinocerebellar ataxia
The CAG expansions that lead to SCA result in a ___-of-function
Gain
Which form of mHtt does sumoylation favor?
Soluble (cytotoxic)
FRXA and Freidreich ataxia are both due to ___ mutations caused by repeat expansions (and occassionally point mut. or deletions)
Null
Freidreich ataxia, FRXA, and MD1 all express a ___ expansion bias
Maternal
Female carriers of fragile x may develop:
Premature ovarian failure
What type of diseases are Huntingtons and SCA?
Polyglutamine
Pathogenesis of polyQ disease is due to interference with:
Transcriptional regulation
When there is no clear inheritance pattern, and traits appear in families more frequently than predicted by chance, the call this ____ inheritance
Non-mendelian
In ____ diseases, other genes and encironmental factors have no effect
Fully penetrant
A description for a trait in which multiple genes each have a limited impact on the phenotype is:
Polygenic traits
A description for a trait in which relatively few genes have an impact on the phenotype is:
Oligogenic traits
A common feature of multifactorial disorders due to interactions of multiple genetic and environmental factors is:
Variable expressivity
Another word for quantitative traits is:
Dichotomous
Four types of studies that can examine qualitative traits are:
Population/migration studies
Adoption studies
Affected family studies
Twin studies
What is the formula for sibling risk ratio?
Prevalence of ds in siblings of affected / prevalence of ds in gen. pop.
What is the name for when two related individuals share a trait?
Concordance
If monozygotic twin concordance is greater than dizigotic twin concordance, this suggests:
Genetic component
If low concordance in MZ and DZ twins, this suggests:
Environmental factors
In monogenic disorders, if only genes are involved, MZ concordance will be ___ and DZ concordance will be ___
100%, 50%
For quantitative, heritability studies, compare the degree of ___ between MZ and DZ twins
Variance
If h^2 is = 1 in a heritability study, the condition is only ____
Genetically determined
If h^2 is = 0 in a heritability study, the condition is only ____
Environmentally determined
What model is used to explain how continuously-distributed, quantitative traits determine a qualitative trait?
Liability threshold model
If liability in an individual exceeds a threshold the disease will occur
The greater the individuals liability above the threshold, the greater the severity of the disease