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[OS 201] 3rd Exam > Trans - Basic Principles of Clinical Genetics > Flashcards

Trans - Basic Principles of Clinical Genetics Flashcards

1
Q

Number of genes in humans

A

30,000

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2
Q

Number of base pairs in human genome

A

31,647 billion base pairs

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3
Q

Percentage of genes coding for proteins

A

less than 2%

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4
Q

Percentage of junk DNA in genome

A

as much as 90%

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5
Q

_____% of bases are exactly identical in all people

A

99.9%

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6
Q

Disease status is influenced by: ___ [2]

A

[1] genetic factors;

[2] environmental factors

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7
Q

Epigenetics

A

Study of heritable changes in gene expression caused by chemical modifications in a chromosome

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8
Q

3 interrelated mechanisms involved in epigenetics

A

[1] DNA methylation;
[2] histone modifications;
[3] activity of miRNA

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9
Q

Significance of miRNA activity in epigenetics

A

[1] miRNAs are encoded within the genome;
[2] miRNA expression is regulated by other epigenetic mechanisms;
[3] miRNAs bind to specific 3’ UTR of an mRNA, and inhibits translation to protein

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10
Q

Characteristics of open chromatin

A

nonmethylated DNA, histones with acetylated tails

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11
Q

Mediates DNA methylation

A

DNA methyltransferase

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12
Q

What heavily influences an individual’s adult health?

A

Early prenatal factors (exposure to certain substances, etc.)

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13
Q

Effect of foliate or choline deficiency in mother’s diet

A

Undermethylation of certain portions of fetal DNA –> abnormalities

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14
Q

What is BPA and what is its effect on agouti mice?

A

Exposure to BPA (Bisphenol A) during early development causes decreased methylation of the agouti gene

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15
Q

The family pedigree is a tool for: [6]

A 
[1] Making a medical diagnosis, 
[2] deciding on testing strategies; 
[3] establishing pattern of inheritance; 
[4] identifying family members at risk; 
[5] calculating risk; 
[6] determining reproductive options
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16
Q

Often the most confusing aspect of pedigree interpretation

A

Non-paternity

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17
Q

Confounding factors in recognizing inheritance patterns [6]

A

[1] variable expressivity;
[2] clinical/genetic heterogeneity;
[3] sex influenced/limited gene expression;
[4] assortative mating (marrying the same looking person);
[5] small paternity size;
[6] lack of information

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18
Q

Usual patterns of inheritance [5]

A 
[1] autosomal dominant; 
[2] autosomal recessive; 
[3] X linked recessive; 
[4] X linked dominant; 
[5] multifactorial
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19
Q

Unusual patterns of inheritance [3]

A

[1] mitochondrial DNA;
[2] triple repeat expansion;
[3] genomic imprinting

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20
Q

Affected genotypes of autosomal dominant inheritance

A

AA or Aa

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21
Q

Characteristics of autosomal dominant inheritance [3]

A

[1] no skipping of generations;
[2] both sexes affected in equal proportions;
[3] may be passed from male to male

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22
Q

If both parents are heterozygous for an autosomal dominant trait, what is the chance that the offspring will be severely affected?

A

25%

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23
Q

Achondroplasia - type of inheritance, site of mutation, characteristics

A

[1] autosomal dominant;
[2] FGF 3;
[3] short stature, skeletal dwarfism, midface hypoplasia, stenosis of spinal canal

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24
Q

Crouzon syndrome - type of inheritance, site of mutation, characteristics

A

[1] autosomal dominant,
[2] FGF 2,
[3] tower head skull (oxycephaly), supraorbital hypoplasia, eye proptosis/exopthalmos

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25
Q

Apert syndrome - type of inheritance, site of mutation, characteristics

A

[1] autosomal dominant;
[2] FGF;
[3] mental handicap, microcephaly, mitten hands

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26
Q

Marfan syndrome - type of inheritance, site of mutation, characteristics

A

[1] autosomal dominant;
[2] fibrillin 1 gene on chromosome 17;
[3] tall stature, scoliosis, arachnodactyly, positive thumb sign, positive wrist sign, dislocation of lens/myopia

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27
Q

Ehlers-Danlos syndrome - type of inheritance, nature of mutation, characteristics

A

[1] autosomal dominant;
[2] defect in collagen synthesis;
[3] cigarette-mark-like wounds on knees, stretchy skin

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28
Q

Affected genotypes of autosomal recessive inheritance

A

aa

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29
Q

Characteristics of autosomal recessive inheritance [3]

A

[1] both sexes affected in equal proportion;
[2] both parents must be carriers of a single copy of the gene for a child to he affected;
[3] risk is 25% per child of carrier parent

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30
Q

Harlequin syndrome - type of inheritance, site of mutation, characteristics, treatment

A

[1] autosomal recessive;
[2] keratin gene;
[3] ichthyosis, pseudo-amputation of digits, ectopion, eclabion;
[4] retinoin

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30
Q

Mucopolysaccharidosis 1 (MPS 1) - also called?; tyoe of inheritance, nature of mutation, characteristics, treatment

A

[1] Hurler’s syndrome;
[2] autosomal recessive;
[3] enzyme deficiency - lysozyme storage disease’
[4] regression of development/loss of developmental milestones, manifests at 2-5 years old;
[5] enzyme replacement treatment

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30
Q

Maple syrup urine disease - type of inheritance, nature of mutation, characteristics

A

[1] autosomal recessive;
[2] lack in enzyme for breakdown of branched amino acids (leucine, isoleucine, valine);
[3] branched chain amino aciduria, maple-smelling urine

30
Q

Galactosemia - type of inheritance, nature of mutation, characteristics, therapy

A

[1] autosomal recessive;
[2] galactose-1-phosphate uridyltransferase deficiency;
[3] early cataracts, enlarged liver;
[4] soy-based milk formula, avoidance of foods with lactose

30
Q

Characteristics of autosomal recessive inheritance [3]

A

[1] both sexes affected in equal proportion;
[2] both parents must be carriers of a single copy of the gene for a child to he affected;
[3] risk is 25% per child of carrier parent

30
Q

For X linked inheritance, where is the gene locus found?

A

X chromosome

30
Q

X linked recessive inheritance is more prevalent in which sex? why?

A

Males, because they only have 1 x chromosome

30
Q

Harlequin syndrome - type of inheritance, site of mutation, characteristics, treatment

A

[1] autosomal recessive;
[2] keratin gene;
[3] ichthyosis, pseudo-amputation of digits, ectopion, eclabion;
[4] retinoin

31
Q

[T/F] x linked recessive inheritance may be transmitted directly from father to son

A

F

31
Q

x linked recessive inheritance - sons of carrier females will have ____ chance of being affected

A

50%

31
Q

[T/F] all daughters of males affected with x-linked inheritance will be affected

A

T

31
Q

[T/F] autosomal dominant traits may skip generations

A

F

31
Q

Duchenne muscular dystrophy - type of inheritance, site of mutation, characteristics

A

[1] x linked recessive;
[2] 60% deletion of dystrophin gene;
[3] exaggerated lumbar lordosis, pseudo-hypertrophy of calf muscle, degeneration of muscles

31
Q

MPS 2 - also called?, type of inheritance,nature of mutation, characteristics

A

[1] Hunter syndrome;
[2] x linked recessive,
[3] mucopolysaccharide storage disease –> enlarged spleen and liver, umbilical hernia, bone marrow invaded by mucopolysaccharides

31
Q

Most common metabolic defect

A

G6PD deficiency

32
Q

[T/F] x linked dominant inheritance - 50% of female children from affected mother will be affected

A

F - 100% will be affected

33
Q

G6PD deficiency - type of inheritance, nature of mutation, characteristics

A

[1] x linked recessive,
[2] mutation in G6PD gene;
[3] no physical defects, no retardation, some medications/food may cause hemolytic anemia

34
Q

[T/F] x linked dominant inheritance - no male children of affected father will be affected

A

T

36
Q

Rett’s syndrome - type of inheritance, site of mutation, characteristics

A

[1] x linked dominant;
[2] MeCP2 gene –> methyl binding for regulation of other genes;
[3] affects females, lethal in males, microcephalis with growth; neurodevelopmental regression, characteristic hand movements

36
Q

[T/F] multifactorial inheritance - most children with traits from this type of inheritance also have affected parents

A

F

37
Q

[T/F] multifactorial inheritance - recurrence risk inreases with the number of affected children in the family. why?

A

T, because if many children have the trait, it probably means that the parents are carrying more copies of the genes needed for the trait to manifest

38
Q

Leigh’s disease - type of inheritance, characteristics

A

[1] mitochondrial DNA inheritance;

[2] progressive loss of mental and movement abilities

39
Q

[T/F] multifactorial inheritance - risk of affected relatives falls off very quickly with the degree of relationship

A

T

41
Q

Spina bifida - type of inheritance, characteristics, treatment

A

[1] multifactorial inheritance;
[2] posterior meningocoele;
[3] immediate closure of the defect

42
Q

Anencephaly - type of inheritance, characteristics, prevention

A

[1] multifactorial inheritance;
[2] skulless, brainless;
[3] folic acid at least 1 month before conception and during pregnancy

43
Q

Oral clefts - type of inheritance, treatment

A

[1] multifactorial inheritance;

[2] surgical correction

43
Q

Mitochondrial DNA is inherited from which parent? Why?

A

Mother, because these mitochondria are derived from the egg’s mitochondria

44
Q

Heteroplasmy

A

Some mitochondria have mutated mtDNA, some do not

45
Q

Mitochondrial DNA codes for: ____ [3]

A

[1] tRNA,
[2] rRNA;
[3] mitochondrial proteins

46
Q

Homoplasmy

A

All mitochondria have either completely normal or completely mutated mtDNA

47
Q

[T/F] mitochondrial DNA inheritance - a father may pass the trait on to his sons

A

F

48
Q

Systems affected by mtDNA disorder

A

Any system that needs ATP/energy

51
Q

Leigh’s disease - type of inheritance, characteristics

A

[1] mitochondrial DNA inheritance;

[2] progressive loss of mental and movement abilities

52
Q

Kearns-Sayre syndrome - type of inheritance, characteristics

A

[1] mitochondrial DNA inheritance;

[2] opthalmoplegia, pigmentary retinopathy, ataxia

55
Q

Myotonic dystrophy - mode of inheritance, nature of mutation, characteristics

A

[1] triple repeat expansion;
[2] CTG repeat;
[3] grip myotonia

56
Q

Fragile X syndrome - mode of inheritance, nature of mutation, characteristics

A

[1] triple repeat expansion;
[2] CGG repeat in fragile site in long arm of X chromosome (FMR1 gene);
[3] mental retardation, speech delay, peculiar movement of arms, autism

58
Q

Prader-Willi syndrome - mode of inheritance, nature of mutation, characteristics

A

[1] genomic imprinting;
[2] q11 to q13 region on paternal chromosome 15 is deleted/unexpressed;
[3] mild mental handicap, insatiable appetite, obesity

59
Q

Angelman syndrome - mode of inheritance, nature of mutation, characteristics

A

[1] genomic imprinting;
[2] q11 to a13 region on maternal chromosome 15 is deleted/unexpressed;
[3] severe mental handicap, happy puppet syndrome

64
Q

Principle of triple repeat expansion

A

Expansion of a segment of DNA that contains a repeat of 3 nucleotides –> high number of repeats causes disease

65
Q

Phenomenon of Anticipation

A

In triple repeat expansion, repeats increase over successive generations and symptoms get worse and worse

68
Q

Principle of genomic imprinting

A

We all inherit two copies of every autosomal gene (one from each parent). Both copies are functional for the majority of these genes; however, in a small subset one copy is turned off in a parent-of-origin dependent manner, causing abnormalities

69
Q

Common manifestation of mitochondrial DNA abnormality

A

Energy-requiring processes of multiple organ systems affected

70
Q

Examples of autosomal dominant disorders [5]

A 
[1] achondroplasia
[2] crouzon syndrome
[3] marfan syndrome
[4] ehlers-danlos syndrome
[5] apert syndrome
71
Q

Examples of autosomal recessive disorders [4]

A

[1] harlequin syndrome
[2] MPS1 / hurler’s syndrome
[3] maple syrup urine disease
[4] galactosemia

72
Q

Examples of x linked recessive disorders [3]

A

[1] duchenne muscular dystrophy
[2] MPS2 / hunter’s syndrome
[3] G6PD deficiency

73
Q

Examples of x linked dominant disorders [1]

A

[1] rett’s syndrome

74
Q

Examples of multifactorial inheritance disorders [3]

A

[1] spina bifida
[2] anencephaly
[3] oral clefts

75
Q

Examples of mitochondrial DNA inheritance disorders [4]

A

[1] leigh’s disease
[2] mitochondrial encelopathy, lactic acidosis, stroke-like episodes (MELAS)
[3] myoclonic epilepsy with ragged red fibers (MERRF)
[4] kearns-sayre syndrome

76
Q

Examples of triple repeat expansion disorders [3]

A

[1] myotonic dystrophy
[2] fragile x syndrome
[3] huntington disease

77
Q

Examples of genomic imprinting disorders [2]

A

[1] prader-willi syndrome

[2] angelman syndrome

[OS 201] 3rd Exam (10 decks)

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