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Medical Genetics > Exam 4 > Flashcards

Exam 4 Flashcards

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1
Q

The majority of inborn errors of metabolism are ___

and are caused by lack of function of a ___ which results in a ___

A
  • Autosomal recessive
  • Protein enzyme
  • Nonfunctional pathway
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2
Q

What are the 7 classifications of metabolic disorders?

A
  1. Carbohydrate Disorders
  2. Amino Acid Disorders
  3. Lipid Disorders
  4. Organic Acid Disorders
  5. Urea Cycle Defects
  6. Energy Production Defects
  7. Heavy Metal Transport Defects
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3
Q

What causes a carbohydrate disorder?

A

Errors in the metabolism of galactose, glucose, fructose, and glycogen OR Mucopolysaccharidoses (lysosomal storage disease)

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4
Q

What causes a lipid disorder?

A

Erros in Metabolism of fatty acids, Biosynthesis of steroids, OR Sphingolipidoses (lysosomal storage disease)

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5
Q

What causes an organic acid disorder?

A

Accumulation of organic acids (carboxylic and sulfonic acids) in blood and urine

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6
Q

What causes urea cycle defects?

A

Disposal of nitrogeous wastes, arginine synthesis

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7
Q

What causes energy production defects?

A

Defects in the oxidative phosphorylation system (mitochondrial system)

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8
Q

What causes heavy metal transport defects?

A

Errors in transport/storage of heavy metals

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9
Q

What type of disorder is Classic Galactosemia?

A

Carbohydrate

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10
Q

Classic Galactosemia is an autosomal recessive, ___ disorder that is located on chromosome ___. It is caused by a mutation in ___ which prevents the effective conversion of ___ (biochemical pathway affected). As a result, ___ is alternatively metabolized into ___.

A
  • Carbohydrate
  • Chromosome 9p13
  • Galactose-1-phosphate uridyl transferase
    (GALT)
  • Galactose to glucose
  • Galactose
  • Galacitol and galactonate
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11
Q

What is the primary means of diagnosis for Classic Galactosemia?

What are the main newborn symptoms?

What happens if symtoms are left untreated?

What is the treatment?

A
  • Newborn screening
  • Poor sucking, Failure to thrive, and Jaundice
  • Sepsis, hyperammonemia, and shock leading to death usually follows
  • Eliminating dietary galactose
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12
Q

What are 2 other carbohydrate disorders?

A

Hypolactasia (adult) and Diabetes mellitus

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13
Q

Mucopolysaccharidoses - Hurler-Scheie Syndrome (MPS-I) is a ___ disorder that is located on chromosome ___. It is caused by a mutation of the ___ gene which encodes the protein enzyme ___. The enzyme hydrolyzes the terminal ___ residues of the
gycosaminoglycans dermatan sulfate and heparan sulfate. Various mutations in the mutated gene carry differing ___ of varying severity based on those mutations inherited.

A
  • Carbohydrate - Lysosomal storage
  • Chromosome 4p16.3
  • IDUA gene
  • α-L-iduronidase
  • α-L-iduronic acid
  • Phenotypical characteristics
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14
Q

What are 2 other Mucopolysaccharisoses disorders?

A

Hunter (MPS-II) and Sanflippo (MPS-III)

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15
Q

Mucopolysaccharidoses - Hurler-Scheie Syndrome (MPS-I) is an autosomal recessive disorder denoted by a ___ in the Punnett square. A proband is diagnosed by symptoms and either ___ for pathogenic variants of IDUA or detection of deficient ___.

A
  • Red individual
  • Molecular genetic testing
  • α-L-iduronidase activity
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16
Q

What are the main symptoms of Mucopolysaccharidoses - Hurler-Scheie Syndrome (MPS-I)?

Treatments can be supportive and symptomatic. Describe the differences between the 2

A
  • Clinical onset between 3-10 yrs, Mild
    intellectual disability, Mild joint and cardiorespiratory disease, Some hearing loss, Coarse face, Hepatosplenomegaly, and/or Corneal clouding
  • Supportive: Stimulating environments for children with MPS-I for early learning
  • Symptomatic: Physical therapy, peaked caps or shades for the eyes, Cardiac valve replacement, tonsillectomy and adenoidectomy for eustachian tube dysfunction and decreased upper respiratory obstructions, etc.
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17
Q

What type of disorder is Phenylketonuria?

A

Amino Acid Disorder

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18
Q

Phenylketonuria is an autosomal recessive, ___ disorder that is located on chromosome ___. It is caused by a mutation in ___ which prevents the effective conversion of ___. As a result, this decreases the function of the ___ (biochemical pathway affected).

A
  • AA disorder
  • Chromosome 12q24
  • Phenylalanine Hydroxylase (PAH)
  • Phenylalanine to tyrosine
  • Phenylalanine Hydroxylation pathway
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19
Q

What is the primary means of diagnosis for Phenylketonuria?

What are the main symptoms?

What is the treatment?

What medication is used?

A
  • Newborn screening using the Guthrie
    microbial assay on dried blood. Virtually 100% correctly diagnosed
  • Newborns: asymptomatic, Adults: Microcephaly,
    Epilepsy, Musty body odor, Eczema, and Severe intellectual disability
  • Remove/restrict phenylalanine from diet: ↓ 2 yrs old 3g/kg/day, ↑ 2 yrs old 2g/kg/day
  • Sapropterin with modified diet
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20
Q

What are 2 other Amino Acid disorders?

A

Maple Syrup Urine Disease and Cystinuria

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21
Q

What type of disorder is MCAD?

A

Lipid disorder

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22
Q

MCAD is an autosomal recessive, ___ disorder that is located on chromosome ___. It is caused by a mutation in ___ which causes ___ that inhibits the
chemical process in the body like ketone bodies and glucose. As a result, ___ is affected (biochemical pathway affected).

A
  • Lipid
  • Chromosome 1p31
  • Acyl-CoA-dehydrogenase (ACADM)
  • Medium fatty acid buildup
  • FA metabolism
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23
Q

What is the primary means of diagnosis for MCAD?

What are the main symptoms?

What is the treatment?

A
  • DNA testing, Newborn Screening
  • Otitis media(infection of ear), lethargy, vomiting,
    gastroenteritis(inflammation of digestive tract), seizures, severity varies
  • Limit fasting periods, low-fat diet, genetic counseling
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24
Q

What are 2 other Lipid disorders?

A

Very-long-chain acyl-CoA dehydrogenase deficiency,
Smith-Lemli-Opitz syndrome (Cholesterol production)

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25
Q

T/F: A person is more likely to have issue with short chain FAs b/c of the complex way they’re taken up in the mitochondria

A

False: very long chain FAs

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26
Q

What type of disorder is Gaucher Type 1?

A

Lipid disorder - Sphingolipidoses (Lysosomal Storage)

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27
Q

Sphingolipidoses - Gaucher Type 1 is an autosomal recessive, ___ disorder that is located on chromosome ___. It is caused by a mutation of the ___ gene which causes an accumulation of ___ b/c it is not properly degraded by the enzyme beta-glucocerebrosidase. As a result, tisues and organs are damaged and ___ is affected (biochemical pathway affected).

A
  • Lipid (lysosomal disease)
  • Chromosome 1q22
  • GBA (Glucosidase Beta Acid)
  • Beta-cerebroside
  • Degradation of sphingolipids
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28
Q

What is the primary means of diagnosis for Sphingolipidoses - Gaucher Type?

What are the main symptoms?

What is the treatment?

A
  • Peripheral blood leukocytes/nucleated cells are tested for a deficiency in Glucocerebrosidase OR Molecular genetic testing (i.e. microarrays): less specific
  • Hepatosplenomegaly, Skeletal abnormality- osteonecrosis to sclerotic lesions, Epistaxis (nosebleed), Anemia
  • Enzyme replacement therapy (ERT) improves symptoms resulting from spleen, liver, and bone involvement, But most treatment options are largely supportive (i.e. blood transfusions for anemia, splenectomy)
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29
Q

What are 2 other Sphingolipidoses (Lysosomal Storage)- Gaucher Type 1 disorders?

A

Tay-Sachs and Niemann-Pick

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30
Q

What type of disorder is Ornithine Transcarbamylase Deficiency?

A

Urea Cycle (there are 5 types of this disorder)

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31
Q

Ornithine Transcarbamylase Deficiency is a ___, urea cycle disorder that is located on chromosome ___. It is caused by a mutation of the ___ enzyme which is used in the urea cycle to catalyze ___ and ___ to create citulline.

A
  • X-linked recessive
  • Chromosome Xp21
  • Ornithine transcarbamoylase (OTC)
  • Carbomyl phosphate and Ornithine
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32
Q

What is the primary means of diagnosis for Ornithine Transcarbamylase Deficiency?

What are the main symptoms?

What is the treatment?

A
  • Ornithine Transcarbamylase Deficiency
  • Hyperammonemia, delayed growth, progressive lethargy, ataxia
  • Low protein diet and ammonia scavenging drugs; like glycerol phenylbutyrate
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33
Q

What is another type of urea cycle disorder?

A

Carbamyl phosphate synthetase deficiency

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34
Q

What type of disorder is Pyruvate Carboxylase Deficiency?

A

Energy Production Defect

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35
Q

Pyruvate Carboxylase Deficiency is an autosomal recessive, ___ disorder that is located on chromosome ___. It is caused by a mutation of the ___ enzyme which is used to convert ___ to ___. As a result, ___ is affected (biochemical pathway affected).

A
  • Energy Production Defect
  • Chromosome 11q13.2
  • Pyruvate carboxylase (PC)
  • Pyruvate to OAA
  • Gluconeogenesis
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36
Q

What is the primary means of diagnosis for Pyruvate Carboxylase Deficiency?

What are the main symptoms?

What is the treatment?

A
  • Physical symptoms, Blood or skin cell samples, Elevated levels of pyruvate and
    lactate in sample (PC enzyme assay)
  • Failure to thrive, Developmental delay, Recurrent seizures, Metabolic acidosis
  • Anaplerotic therapy (restricting/removing from diet), Hydration, Correction of the metabolic acidosis

*Know that there are different types of the disease, meaning variability in expression

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37
Q

What is another type of energy production defect disorder?

A

Cytochrome c oxidase deficiency

38
Q

What type of disorder is Hereditary Hemachromatosis?

A

Heavy Metal Transport Defect

39
Q

Hereditary Hemachromatosis is an autosomal recessive, ___ disorder that is located on chromosome ___ in the ___ region. It is caused by a mutation of the ___ allele which is linked to the causative gene HFE. This usually binds to ___ . As a result of the mutation, the small intestine ___ due to a defect in the regulation of iron. is affected (biochemical pathway affected).

A
  • Heavy Metal Transport Defect
  • Chromosome 6p.21
  • Major Histocompatibility Region (MHC)
  • HLA-A3 (Human Leukocyte Antigen)
  • Hepcidin (iron regulation)
  • Excessively absorbs iron
40
Q

What is the primary means of diagnosis for Hereditary Hemachromatosis?

What are the main symptoms?

What is the treatment?

A
  • Liver biopsy accompanied by histochemical staining for hemosiderin, Abnormal serum iron levels in blood
  • Fatigue (most common), Joint pain, Diminished libido, Diabetes, Increased skin pigmentation
  • Serial phlebotomy, Iron-chelating agent (deferoxamine)
41
Q

What are 2 other types of Heavy Metal Transport Defect disorder?

A

Wilson Disease and Menkes Disease

42
Q

Define Polygenic

A

Multiple genes contribute to a trait

43
Q

Define multifactorial diseases

A

Polygenic + environmental factors contribute to a trait

44
Q

What is a quantitative trait?

A

Measured on a continuous
numerical (sliding) scale (e.g. blood pressure, height)

45
Q

T/F: Most quantitative traits are multifactorial but not all multifactorial traits are quantitative

A

True

46
Q

Explain the multifactorial model

A

Many possible phenotypes (differing
slightly) with population distribution having a bell shaped curve

47
Q

Describe the threshold model

A

“Threshold of liability” must be crossed (combination of specific gene alleles and environmental
factors) for the disease to be
expressed

48
Q

___ is an example of the threshold model because it demonstrates that ___ are less affected but their ___ relatives would have a higher risk of developing the disease due to them having more risk factors

A
  • Pyloric stenosis
  • Females
  • Male
49
Q

Single gene recurrence risks are given with ___ whereas multifactorial diseases use ___. These are used based on ___ of data as opposed to Mendelian inheritance principles

A
  • Confidence
  • Empirical risks
  • Direct observation
50
Q

What are 2 reasons why recurrence risks of multifactorial diseases are variable between different populations?

A
  • Allele frequency
  • Environmental factors
51
Q

How does a neural tube defect occur?

What is the prevalence rate of neural tube defects (NTDs)?

How are NTDs diagnosed?

A
  • Defect in closure or reopening of the neural tube
  • 1/1000
  • Ultrasound or by elevation in a-fetoprotein (AFP) in amniotic fluid
52
Q

What is the most common type of NTD?

A
  • Spina bifida
53
Q

Describe the NTD Anencephaly

A

Partial or complete absence of the cranial vault and calvarium and partial or complete absence of the cerebral hemisphere

54
Q

Describe the NTD Encephalocele

A

Protrusion of the brain into an enclosed sac

55
Q

Studies found that if mothers use this they can dramatically decrease the risk of NTD

A

Folic acid

56
Q

What 5 criteria regarding recurrence risks are used to define multifactorial inheritance?

A
  1. Recurrence risk is higher if more than one family
    member is affected
  2. If the expression of the disease in the proband is more severe, the recurrence risk is higher
  3. Recurrence risk is higher if the proband is of the less commonly affected sex
  4. Recurrence risk usually decreases rapidly in more remotely related relatives
  5. If population prevalence is f (which varies between 0-1), then recurrence risk in offspring and siblings of probrand is √f
57
Q

Some disease cases can be influenced by both a single gene with large/numerous effects, and multifactorial background (multiple other genes + environmental factors) with a smaller effect. This is called a ___

Give 3 examples of this.

A
  • Major gene
  • Breast cancer, Colon cancer, Heart disease
58
Q

How are relative influences of genes determined (apart
from environmental factors)?

A

Twin and Adoption studies

59
Q

Differences between ___ should be due only to environmental effects whereas ___ should differ in genes and environmental effects

A
  • MZ twins
  • DZ twins
60
Q

Define concordant and disconcordant

A
  • Concordant: Both members of a twin pair share a trait
  • Disconcordant: Both members of a twin pair have different traits for a characteristic
61
Q

What is a concordance rate?

A

The percentage of absent or present traits

62
Q

What is a correlation coefficient?

A

Used for measuring quantitative traits (height, weight) between twins. Ranges from -1.0 to +1.0

63
Q

For a trait determined completely by genes, MZ twins should always be concordant (have identical
genes) with the exception of ___

*concordance rate 1.0, correlation coefficient of 1.0

A

Somatic mutations

64
Q

DZ twins concordant rate is less often than MZ. Therefore only __% of their genes are identical

A

50%

*concordance rate and correlation coefficient 0.5

65
Q

The percentage of the population variation in a trait that is due to genes

A

Heritability

66
Q

How is heritability calculated?

A

From concordance rates and
correlation coefficients for MZ and DZ twins

67
Q

Values closer to ____ indicate that a trait is
determined almost entirely by genes

A

1.0

68
Q

__% of newborns present with a congenital malformation. Most congenital malformations are considered ___

A
  • 2%
  • Multifactorial
69
Q

What are the 2 classifications for congenital malformations?

A
  • Easily repaired when identified at birth
  • More severe consequences
70
Q

What 3 families of genes are genetic components of congenital malformations?

What gene is a proto-oncogene (Hirschsprung Disease)

A
  • HOX, PAX, TBX
  • RET
71
Q

Fill in the blank for environmental factors that contribute to congenital malformations:

___ = severely shortened limbs

___ = heart, ear, CNS defects

___ = heart defects

A
  • Thalidomide
  • Retinoic acid
  • Rubella infection
72
Q

What are 3 common types of cardiovascular disorders?

A
  • Heart Disease: coronary heart disease (CAD), cardiomyopathy
  • Stroke
  • Hypertension
73
Q

Coronary artery disease is caused by ___ which is a narrowing of coronary arteries due to lipid-laden lesions. This leads to leads to ___ (hypoxia and death of heart muscle)

A
  • Atherosclerosis
  • Myocardial infarction
74
Q

What are known risk factors for coronary artery disease?

Factors that decrease risk?

A
  • Obsesity, Cigarette smoking, Hypertension,
    Elevated blood cholesterol, Positive family history
  • Exercise and diet low in saturated fats

*Fact: 60% reduction in age adjusted mortality due to CAD and stroke since 1950

75
Q

What are the main 2 genetic factors that contribute to coronary artery disease?

A
  • **Low density lipoprotein (LDL)
    receptor: **familial hypercholesterolemia
  • Apolipoprotein B: increases circulating LDL cholesterol

*Other factors: Genes whose products contribute to inflammation, Other Lipoprotein genes

76
Q

T/F: One affected first degree relative doubles the recurrence risk for females

A

True

77
Q

What are the genetic factors of breast cancer?

A

BRCA1 and BRCA2 genes (homologous DNA repair)

78
Q

What are the environmental factors of breast cancer?

A
  • Nulliparity
  • Increased maternal age
  • High-fat diet
  • Alcohol use
  • Estrogen replacement therapy
79
Q

___ is 2nd only to lung cancer in annual cancer deaths

A

Colorectal

80
Q

A mutation in what gene causes familal colorectal cancer?

A

APC tumor suppressor gene

81
Q

Prostate cancer deals with SNPs associated with ____ oncogene transcription located on ____. Heritability is estimated to be ____.

A
  • MYC
  • Chromosome 8
  • 0.4 (40%)
82
Q

Diabetes Mellitus is a ___ group of disorders and the leading cause of ___.

A
  • Heterogeneous
  • Adult blindness
83
Q

What are the 3 major types of diabetes mellitus?

A
  • Type 1 (formerly “insulin dependent”) (autoimmune disorder)
  • Type 2 (formerly “non-insulin dependent”) (more familal clustering)
  • Maturity onset diabetes of the young (MODY)
84
Q

What are the 3 features unique to type 2 diabetes?

A
  • Some “endogenous” insulin production
  • Cells have difficulty using insulin – “insulin resistance”
  • Obesity is a common co-morbidity
85
Q

What are the most important risk factors for type 2 diabetes?

What reduces risk?

A
  • Positive family history and obesity
  • Exercise reduces risk – combats obesity, increases insulin sensitivity, improves glucose tolerance
86
Q

What are the genetic factors of type 2 diabetes?

A
  • >70 genes linked to increased susceptibility
  • TCF7L2 – product is a transcription factor involved in insulin secretion
  • PPAR-γ – nuclear receptor involved in adipocyte differentiation, glucose metabolism
87
Q

What percentage of American adults are overweight?

A

70% BMI >25

88
Q

Obesity not considered a “disease” – but is a co-morbidity and risk factor for:

A
  • heart disease
  • stroke
  • type 2 diabetes
  • cancers – prostate, breast, colon
89
Q

Regarding obesity, heritability of body weight is estimated to be between ___ and ___

What type of studies have supported a strong genetic component to obesity?

A
  • 0.6 and 0.8
  • Adoption
90
Q

What are 5 types of multifactorial diseases?

A
  • Alzheimer’s Disease
  • Alcoholism
  • Schizophrenia
  • Bipolar disorder
  • Autism Spectrum Disorder (now including Asperger syndrome)

Medical Genetics (4 decks)

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