Biochemistry - Genetics Flashcards by Robin Sautter

Uniparental disomy

Offspring receives 2 copies of a chromosome from 1 parent and no copies from the other parent

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Hardy-Weinberg population genetics

If a population is in Hardy-Weinberg equilibrium and if p and q are the frequencies of separate alleles, then:

p-squared + 2pq + q-squared = 1 and p +q = 1

p-squared = frequency of homozygosity for allele p
q-squared = fréquence of homozygosity for allele q
2pq = frequency of heterozygosity

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What are the Hardy-Weinberg law assumptions?

No mutation occurring at the locus
Natural selection is not occurring
Completely random mating
No net migration

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Imprinting

Imprinting/Inactivation by methylation

only one allele active and the other is inactive

With one allele inactivated, deletion of the active allele –> disease

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What is the pathogenesis of Prader-Willi Syndrome?

maternal imprinting

mutation on chromosome 15 of PATERNAL gene

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What are symptoms of Prader-Willi Syndrome?

hyperphagia
obesity
intellectual disability
hypogonadism
hypotonia

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What is the pathogenesis of AngelMan Syndrome?

paternal imprinting

mutation on chromosome 15 of MATERNAL gene

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What are symptoms of AngelMan Syndrome?

inappropriate laughter
seizures
ataxia
severe intellectual disability

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What mode of inheritance affects both male and females in all generations?

What is the inheritance often due to?

autosomal dominant

due to structural genes

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What mode of inheritance is usually only seen in 1 generation?

What is the inheritance often due to?

autosomal recessive

enzyme deficiencies

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What mode of inheritance results in sons of heterozygous mothers having a 50% chance of being affected?

X-linked recessive

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Can male-to-male transmission occur in X-linked recessive?

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Effects in a male from an X-linked recessive inheritance are more or less severe?

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What is mitochondrial inheritance?

transmitted only through the mother

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Who shows signs of disease in mitochondrial inheritance?

All offspring of affected females may show signs of disease

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What diseases are associated with mitochondrial inheritance?

Mitochondrial myopathies (rare disorders)

often present with myopathy, lactic acidosis, and CNS

secondary to failure in oxidative phosphorylation

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What can be seen on muscle biopsy of a mitochondrial myopathy?

“ragged red fibers”

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What are autosomal dominant diseases (alphabetical order)?

Autosomal Dominant Polycystic Kidney Disease (ADPKD)- chrom 16
Familial Adenomatous Polyposis - chrom 5
Familial Hypercholesteremia 
Hereditary spherocytosis
Huntington's Disease
Marfan Syndrome
Multiple Endocrine Neoplasias
Neurofibromatosis Type 1
Neurofibromatosis Type 2
Tuberous sclerosis
von Hippel-Lindau Disease

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What are autosomal recessive diseases (alphabetical order)?

albinism
ARPKD
CF
glycogen storage diseases
hemochromatosis
Kartagener Syndrome
mucopolysaccharidoses
PKU
sickle cell anemia
sphingolipidoses
thalassemias
Wilson Disease

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What is the most common lethal genetic disease in Caucasian population?

Cystic fibrosis

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What is the defect in CF?

defect in CFTR gene on chromosome 7

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What are signs to diagnose CF?

Study These Flashcards

increased Cl- concentration in sweat = diagnostic!
contraction alkalosis and hypokalemia (similar to a diuretic in that H2O/Na+ losses results in concomitant renal K+/H+ wasting)

What are complications of CF?

Study These Flashcards

recurrent pulmonary infxns (e.g. Pseudomonas)
chronic bronchitis and bronchiectasis --> reticulonodular pattern on CXR
pancreatic insufficiency
malabsorption and steatorrhea
nasal polyps
meconium ileus in newborns
infertility in males
Fat soluble vit. deficiencies (ADEK)

What is the treatment for CF?

Study These Flashcards

N-acetylcysteine - loosens mucus plugs
dornase alfa (DNAse) - clear leukocytic debris

What are X-linked Recessive diseases?

``` Bruton agammaglobulinemia Wiskott-Aldrich Syndrome Fabry Disease G6PD Deficiency Ocular albinism Lesch-Nyhan Syndrome Duchenne (and Becker) muscular dystrophy Hunter Syndrome Hemophilia A and B Ornithine transcarbamylase deficiency ```

What is the pathogenesis of Duchenne Muscular Dystrophy?

X-linked frameshift mutation --> truncated dystrophin --> accelerated muscle breakdown

What tests are needed to confirm Duchenne Muscular Dystrophy?

Western blot and muscle biopsy

What lab findings will you see in Duchenne Muscular Dystrophy?

Increased CPK and aldolase

When do DMD symptoms begin?

Before age 5

What is the pathogenesis of Becker Disease?

X-linked POINT mutation --> defunct dystrophin protein --> less severe than Duchenne Muscular Dystrophy

When do Becker Disease symptoms begin?

adolescence or early adulthood

What is the pathogenesis of myotonic type 1 disease? This is an example of muscular dystrophy.

CTG trinucleotide repeat expansion in the DMPK gene -> abnormal expression of myotonic protein kinase --> myotonia, muscle wasting, frontal balding, cataracts, testicular atrophy, and arrhythmia

What is the pathogenesis of Fragile X Syndrome?

X-linked defect affecting the methylation and expression of the FMR1 gene

What is a major finding of Fragile X Syndrome?

2nd most common cause of genetic intellectual disability (after Down syndrome)

What are physician findings of Fragile X Syndrome?

``` enlarged testes long face with a large jaw larged everted ears autism mitral valve prolapse ```

What are diseases with trinucleotide repeat expansions?

Huntington disease Myotonic dystrophy Friedrich ataxia fragile X syndrome Try Hunting for my fried eggs.

What is the MC cause of genetic intellectual disability?

Down Syndrome

What trisomy is associated with Down Syndrome?

Trisomy 21

What is the usual cause of Down Syndrome?

meiotic nondisjunction of homologous maternal age

What are the lab findings during pregnancy with a diagnosis of Down Syndrome?

1st trimester - increased nuchal translucency and hypo plastic nasal bone, serum PAPP-A is decrease and free beta-hCG is increased 2nd trimester - increased beta-hCG and estriol and decreased inhibin A and alpha-fetoprotein

What trisomy is associated with Edwards Syndrome?

Trisomy 18

What are some signs of Edwards Syndrome?

low set ears micrognathia intellectual disability rocker bottom feet

What are the labs associated with Edwards Syndrome?

Decreased alpha-fetoprotein, estrial, beta-HCG, and inhibin-A

What trisomy is associated with Patau Syndrome?

Trisomy 13

What are some signs of Patau Syndrome?

``` rocker bottom feet polydactyly micropthalmia cleft lip/palate intellectual disability ```

What is a Robertsonian Translocation? What can it result in?

nonreciprocal chromosomal translocation where long arms of acrocentric chromosomes fuse at the centromere and the 2 short arms are lost results in miscarriage, stillbirth, and chromosomal imbalance (e.g. Down Syndrome)

What genetic abnormality is associated with Cri-du-chat Syndrome?

micro deletion of short arm of chromosome 5

What are some findings of Cri-du-chat Syndrome?

``` microcephay mod-severe intellectual disability high pitched crying/mewing* ("cry of the cat") cardiac abnormalities (VSD) epicanthal folds ```

What genetic abnormality is associated with Williams Syndrome?

micro deletion long arm of chromosome 7

What are some findings of Williams Syndrome?

``` "elfin" facies hypercalcemia extreme friendliness w/ strangers cardiac abnormalities well-developed verbal skills intellectual disablity ```

What are the syndromes associated with deletions at 22q11?

DiGeorge Syndrome and Velocardiofacial Syndrome

What is the pneumonic and findings associated with the 22q11 deletion diseases?

CATCH-22 ``` Cleft palate Abnormal facies Thymic aplasia Cardiac abnormalities Hypocalcemia (d/t no parathyroids) Deletion at chrom. 22 ```

What is the cause of DiGeorge Syndrome embryologically?

Failure of 3rd and 4th pharyngeal pouches to develop

Biochemistry - Genetics Flashcards

(53 cards)