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Genetic Conditions Flashcards

1
Q

List the ethical issues surrounding genetic testing

A
  • Detection of false paternity
  • Stigmatization (including survivors’ guilt)
  • Loss of employment or insurance
  • Psychological harm
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2
Q

Diagram the relationship between the DNA molecule and chromosomes

A

Every chromosome in the body is composed of 1 DNA helix; most of the time DNA is in interphase and is just a big double helix; chromosome structure does not represent what is happening in most cells

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3
Q

Chromosome disorders

A

Abnormalities in # of structure of chromosomes

  • <1%
  • ie. trisomy 21
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4
Q

Single gene disorders

A
  • (usually) affect protein function

- Mendelian inheritance (ie. autosomal dominant, and sex-linked)

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5
Q

Multifactorial disorders

A
  • Combination of both genes and environment
  • Common; ie. CAD, cancer, dementia
  • Polygenic
  • Teratogenic (environmentally based)
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6
Q

Mitochondrial disorders

A
  • Disrupted by same mutational mechanisms as nuclear DNA
  • Maternal inheritance if mutations in mitochondrial DNA; Mendelian inheritance if mitochondrial gene on nuclear DNA
  • ETC genes
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7
Q

Karyotyping

A

Detects alterations in #, large duplications/deletions, translocations

–>use B cell lymphocytes, add mitogen to stimulate cell division, add colchicine to stop in metaphase; stain with gemsatrypsin to digest some histones

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8
Q

FISH

A

Fluorescent in situ hybridization

Detects small cytogenetic changes that are invisible on karyotype

Use probe of interest + control probe

If probe hybridizes to the sample, the DNA sequence is present

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9
Q

How would you use FISH to test for WIlliams syndrome

A

add probe for elastin gene. If more green, elastin gene not in patient DNA and patient has WIlliams

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10
Q

CGH

A

Comparative Genomic Hybridization

  • used for deletions of extra DNA
  • take patient DNA and control DNA and put in systematically ordered wells
  • below 0 –> deletion
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11
Q

Exome Sequencing

A

sequence coding portion of the human genome

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12
Q

Mendelian single gene inheritance

A

autosomal or sex-linked, dominant or recessive

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13
Q

Germline mosaicism

A

presence of more than one genetically distinct cell line in germ cells

someone can have mutation but not sow it, and then pass on mutated germ line

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14
Q

What are characteristic features of Autosomal Dominant Pedigrees

A
  • no skipped generations
  • equal male/female affectedness
  • new mutations common, many times due to germ-line mutations
  • 50% of children of affected individuals also affected
  • sometimes reduced penetrance or variable expressivity
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15
Q

What are characteristics of autosomal recessive pedigrees

A
  • skipping of generations
  • possible consanguinity
  • male and females equally affected
  • affected individuals have 100% chance of transmitting mutated gene
  • usually complete penetrance
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16
Q

PKU has what type of inheritance

A

autosomal recessive

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17
Q

PKU is a deficiency of ___

A

phenylalanine hydroxylase (converts Phe–> Tyr)

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18
Q

Clinical features of PKU include

A

brain damage; sometimes musty odor, eczema, hypopigmentation

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19
Q

What is the prognosis of someone with PKU?

A

Good if maintain diet low in protein (esp. Phe)

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20
Q

What is the genetic pathogenesis of Cystic fibrosis?

A

point mutation in CFTR gene, which codes for chloride channel)

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21
Q

Cystic fibrosis has what kind of inheritance?

A

Autosomal recessive

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22
Q

What non-genetic test is used to test for cystic fibrosis

A

sweat chloride test

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23
Q

What is a heterozygous advantage of cystic fibrosis

A

protection against diarrheal diseases (ie. Typhoid, cholera)

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24
Q

What are the clinical features of Cystic Fibrosis

A

Neonatal: meconium ileus, abdominal calcifications; infancy: failure to thrive, chronic diarrhea, pneumonia;

childhood: nasal polyposis, intussusception;

adolescence & adulthood: nasal polyposis,, bronchiectasis, delayed puberty, azoospermia

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25
Q

What type of inheritance is Achondroplasia?

A

Autosomal dominant

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26
Q

Achondroplasia affects the _____ gene, which is a (positive/negative) regulator of bone grown

A

FGFR3; negative

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27
Q

Short-limbed dwarfism; rhizomelic shortening of arm and legs, macrocephaly, frontal bossing, depressed nasal ridge, and CNS complications are all features of _________

A

Achondroplasia

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28
Q

True or False: the majority of achondroplasia cases are due to germline mosaicisms

A

False; 80% are de novo mutations

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29
Q

Retinoblastoma has what type of inheritance?

A

autosomal dominant

has reduced penetrance

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30
Q

Neurofibromatosis type 1 has what kind of genetic inheritance?

A

autosomal dominant

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31
Q

Patient presents with
Cafe-au-lait macules, axillary/inguinal freckling, Neurofibromas, Lisch modules (iris hamartomaas), Bony lesions (tibial bowing). what does he likely have?

A

Neurofibromatosis type 1

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32
Q

Male patient presents with Dilated aortic root, ectopia lentis, skeletal changes, dural ectasia. What does he likely have?

What is the risk his new baby have of also being affected if his wife is homozygous normal?

A

Marfan Syndrome

50%

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33
Q

True/False: heterozygotes of sickle cell anemia have the same problems as homozygous for the mutation

A

False: heterozygotes have 40% HbS and are protected against Malaria

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34
Q

Reduced penetrance

A

not everyone who carries a mutation will express the phenotype of the mutation

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35
Q

Variable expressivity

A

there can be different phenotypic expressions of the same mutations

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36
Q

Consanguinity

A

When 2 people have blood relation to one another (& know it)

Increases risk for offspring with recessive phenotypes

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37
Q

De Novo mutations

A

New mutations; make inheritance patterns hard to see, 50% occurence

an explanation when kid has something but parents unaffected

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38
Q

If more than one child is affected by a genetic disorder, and both parents have been genetically tested normal, disorder likely due to ______ ______

A

Germline mosaicism

presence of more than one genetically distinct cell line

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39
Q

Elevated _______ is a sign of an organic acid disorder where methylmalonyl-CoA mutase is deficent;

A

MMA (methylmalonic acid)

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40
Q

Elevated Methylmalonic acid is treated by

A

a low protein diet

41
Q

One example of a Urea Cycle defect is _______; this will show elevated _____ in the labs

A

Ornithine transcarbamylase deficiency (OTC); ammonia

42
Q

Urea cycle defects are treated with (2 things)

A

low protein diet and ammonia scavenger meds

43
Q

Restricting fruits, certain vegetables, corn syrup, and table sugar will help what sort of carbohydrate disorder?

A

hereditary fructose intolerance

44
Q

Lesch-Nyhan disease is a (purine/pyrimidine) disorder

A

purine

45
Q

A low purine diet, allopurinol and meds for neurologic symptoms will help what disease?

A

Lesch-Nyhan

46
Q

Medium chain acyl-CoA dehydrogenase is easily treated by:

A

avoiding fasting; rapidly treating hypoglycemia

47
Q

Lethargy and vomiting following a fast, as well as hypoketotic hypoglycemia show indication for:

A

medium chain acyl-CoA dehydrogenase (MCAD) deficiency

48
Q

Lack of biotinidase will cause biotin deficiency or toxicity?

A

deficiency

[supplement with biotin to treat]

49
Q

“Gargoylism,” a phenotypic expression of elevated mucopolysaccharides is present in _____ disorder;

it is treated with

A

Hunter syndrome

Enzyme replacement therapy

50
Q

more than 95% of cases are due to non-familial nondisjunction

A

Trisomy 21

51
Q

True of False: incidence of Down Syndrome is 1/800 live births

A

True

52
Q

Describe 46, XY t(14;21) and 46, XXt(21;

A

4% of Down cases; due to translocation of 3rd 21 chromosome to another chromosome

phenotypically normal parents

Mother with 45,XX,t(21;21) would have 100% chance of child with Down (would pass 0 and child aborts or 2)

53
Q

Hunter syndrome has what kind of genetic inheritance?

A

x-linked recessive

54
Q

Lesch-Nyhan disease has what kind of genetic inheritance?

A

x-linked recessive

55
Q

OTC deficiency has what kind of genetic inheritance?

A

x-linked recessive

56
Q

T/F: Trisomy 18 (Edwards) is has 1/5-7000 incidence

A

True

57
Q

Trisomy 13 (Patau) has 1/10-20,000 incidence

A

True

58
Q

Name the syndrome based on the features:

  • upslanting palpebral fissures
  • single palmar transverse creases
  • congenital heart disease (40-50%)
  • hearing loss due to otitis media
  • strabismus
  • hypothyroidism
  • moderate intellectual disablitiy
A

Down syndrome

59
Q

Name the syndrome based on the features:

  • low frontal hairline
  • short palpebral fissures
  • blunt nasal tip
  • small nostrils
  • small chin
  • “fawn-like” ears
  • high nasal bridge
A

Trisomy 18 (Edwards Syndrome)

60
Q

Name the syndrome based on the features:

  • holoprosencephaly
  • microcephaly
  • non-typical cleft
  • short prominent sternum
  • omphalocele
  • micropenis
  • “rocker-bottom” feet
  • Ventricular septal defect
  • cystic dysplastic kidneys
A

Trisomy 13

61
Q

Name the syndrome based on the features:

  • Cat-like cry
  • hypotonia
  • laryngeal abnormality
  • growth restriction
  • microcephaly
  • round face with widely spaced eyes
  • single palmar creaes
  • moderate to severe intellectual disability
A

5p- syndrome (Cri du chat)

62
Q

Name the syndrome based on the features:

  • Tetralogy of Fallot
  • interrupted aortic arch
  • ventricular septal defect
  • anomalies in branchial arch and pharyngeal pouches
  • Long narrow face w/ tubular nose
  • Cleft palate
  • hypocalcemia
A

22q11.2

63
Q

22q11.2 is due to

A

non-allelic homologous recombination

90% have 3Mb deletion

64
Q

Name the syndrome based on the features:

  • Wilms tumor of kidney
  • Aniridia
  • Genital anomalies
  • Retardation of growth and development
A

WAGR syndrome

deletion at 11p13

65
Q

Name the syndrome based on the features:

  • cocktail personality
  • hypercalcemia
  • supravalvular aortic stenosis
  • long philtrum
  • uncanny musical abilities
  • blue eyes with stellate pattern
  • wide mouth
  • eye puffiness
A

Williams syndrome

varying size deletion on chromosome 7q11

sometimes includes ELN deletion

66
Q

Klinefelter syndrome

karytoype & features

A

(47,XXY)

small firm tsticles, relatively long legs, gynecomastia, hypogenitalism, azospermia

67
Q

Turner syndrome

A

(45,X)
Hand and feet edema at birth, webbed neck, lack of puberty, short stature, abnormally formed nails, coarctation of aorta, increased nuchal fold, streak gonads, infertility

68
Q 
Patients with (47,XXX) are infertile.
(T/F)
A

False; generally normal fertility

no phenotype

69
Q 
Patients with (47,XYY) are infertile.
(T/F)
A

False

70
Q

How do you get a 46 XY female?

A

SRY is deleted in crossing over

71
Q

How do you get a 46 XX male?

A

SRY crosses over to X in meiosis in male

72
Q

Describe when karyotyping is useful``

A
  • when you want to detect a large scale change

- structural & numeric changes

73
Q

Describe when you would use FISH

A

to detect small, specific cytogenetic changes

74
Q

Which color is the control probe and the FISH probe

A

Control probe is green; FISH probe is red

75
Q

When would you use CGH or microarray analysis

A
  • when you want a broad overview with high resolution
  • labeled patient & control DNA are competitively hybridized to an array, revealing gains or losses of genetic material
  • Cannot detect balanced translocations
76
Q

Why would you use FISH for a patient with Turner syndrome?

A

do detect any presence of Y chromosome, because will increase the risk for gonadoblastoma

77
Q

Why do females have more varying phenotypic/disease expression for X-linked conditions compared to males?

A

because of the inactivation of one X chromosome (Barr bodies) in female cells

78
Q

inactive X-chromosome

A

Barr body

79
Q

Reducing X-chromosome expression to 1 of the alleles

A

Dosage compensation

80
Q

differing expression of chromosomes in (somatic) cells across the body

A

Mosaicism

81
Q

What type of inheritance is hemophilia

A

x-linked recessive

82
Q

Reduced factor VIII is present in what condition?

A

Hemophilia A

83
Q

Name the disorder based on the symptoms: normal at birth, progressive muscle weakness, pseudohypertrophy, respiratory insufficiency

A

Duchenne Muscular dystrophy

84
Q

What type of inheritance does Duchenne Muscular dystrophy have?

A

x-linked recessive

85
Q

What kind of inheritance is red-green-colorblindness

A

x-linked recessive

86
Q

Name the disorder based on the symptoms: skin redness and blisters, progressing to thickened skin, then hyperpigmentation

seen only in females

A

incontinentia pigmenti

seen only in females bc x-linked dominant

87
Q

Why is genetic variation important for evolution and speciation

A

important for evolution and speciation

88
Q

p stands for _____
p2 stands for _____
q stands for _____
q2 stands for

A
  • allele frequency of dominant allele
  • percent of pop homozygous dominant
  • allele frequency of recessive allele
  • percent of pop homozygous recessive
89
Q

List the assumptions required for Hardy-Weinberg Law

A 
Random mating
large population
no mutations
no selection against any phenotypes
no migration
autosomal locus
90
Q

What is assortative mating

A

when similar conditions/groups mate (ie. deafs)

91
Q

How is inbreeding different that consanguinuity

A

inbreeding occurs in small geographic areas. Consanguinity occurs when a couple knows they are related

92
Q

Explain genetic drift and the Founder Effect

A

when someone with/carrier of condition goes off and starts new population, allele frequency can increase in subsequent generations

93
Q

Which autosomal recessive condition is found commonly in North European Caucasians?

A

Cystic fibrosis

94
Q

What is the heterozygous advantage of the Cystic fibrosis carriers?

A

protection against diarrheal conditions

95
Q

What is the heterozygous advantage of the carriers of sickle cell anemia?

A

protection against malaria death

96
Q

Tay-Sachs is highly prevalent in what population?

A

Ashkenazi Jews

97
Q

Which group has a higher incidence of Maple-Syrup urine disease?

A

Mennonites

98
Q

Which ethnic group is more likely to have a mutation in the MPV17 gene? Why?

A

Navajos. Genetic drift/founder effect

FMS (3 decks)

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