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MOD Final > Genetics (Part I) > Flashcards

Genetics (Part I) Flashcards

1
Q

There are three categories of human genetic disorders. What are they?

A

Mutation in a single gene with large effects (aka mendelian DOs); Chromosomal DOs; Complex multigenic DOs

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2
Q

What are 6 examples of complex multigenic DOs?

A

Atherosclerosis, diabetes, hypertension, autoimmune diseases, height, and weight

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3
Q

What do mutations in germ cells give rise to?

A

Inherited disease

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4
Q

What do mutations in somatic cells give rise to?

A

Cancer and some congenital malformations

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5
Q

What is a missense mutation?

A

When you alter the meaning of the sequence of the encoded protein

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6
Q

What is a nonsense mutation?

A

When you insert a stop codon where it does not belong

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7
Q

What is a great example of a missense mutation?

A

The one that occurs with sickle cell anemia: glutamic acid is changed to valine in the beta-globin chain of Hgb

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8
Q

What is a great example of a nonsense mutation?

A

When a beta-globin chain gets changed to beta-thalassemia

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9
Q

Where do the mutations of the noncoding sequences take place?

A

Usually in the promoter or enhancer sequence; sometimes it can be a defective splicing of intervening sequences

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10
Q

What occurs in a mutation of a noncoding sequence?

A

There will be failure to form mRNA, so there is no translocation; or there will be changes to transcription factors such as MYC, JUN, or p53

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11
Q

What happens if there is a deletion or insertion of base pairs in a multiple of 3 occurs?

A

The reading frame is intact and you just get an abnormal protein

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12
Q

What happens if there is a deletion or insertion of base pairs not in a multiple of 3?

A

There is alteration in the reading frame and you get a frameshift mutation

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13
Q

What is a trinucleotide repeat?

A

Amplification of a sequence of 3 nucleotides

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14
Q

What is associated with trinucleotide repeats?

A

Anticipation- when a genetic disorder is passed on to the next generation, the symptoms become apparent at an earlier age with each generation

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15
Q

What are 2 main examples of diseases caused by trinucleotide-repeats and have anticipation?

A

Huntingtons disease and myotonic dystrophy

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16
Q

What is codominance?

A

When both alleles contribute to a phenotype

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17
Q

What is pleiotropism?

A

When a single mutant gene has many end effects

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18
Q

What is genetic heterogeneity?

A

Mutations at several loci may produce the same trait

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19
Q

There are three transmission patterns of single gene disorders. What are they?

A

Autosomal dominant, autosomal recessive, and X-linked

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20
Q

What are 2 examples of autosomal dominant disorders that affect the nervous system?

A

Huntington disease and neurofibromatosis

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21
Q

What are 3 examples of autosomal dominant disorders that affect the skeletal system?

A

Marfan syndrome, Ehlers-Danlos syndrome, and osteogenesis imperfecta

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22
Q

What is 1 example of an autosomal dominant disorder that affect the metabolic system?

A

Familial hypercholesterolemia

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23
Q

Autosomal dominant disorders are manifested in what state?

A

Heterozygous- so at least one parent is usually affected

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24
Q

When do new autosomal dominant mutations tend to occur?

A

In germ cells of relatively older fathers

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25
Q

There are variations in penetrance and expressivity in autosomal dominant disorders. What is incomplete penetrance?

A

When there is a mutation but a normal phenotype

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26
Q

There are variations in penetrance and expressivity in autosomal dominant disorders. What is variable expressivity?

A

Everybody has a trait, but it is expressed differently

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27
Q

What is the best example of variable expressivity?

A

Neurofibromatosis type 1: patients could have café-au-lait spots or not, skeletal deformities or not, and/or neurofibromas

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28
Q

Sometimes with autosomal dominant disorders you can get decreased product, dysfunctional, or inactive product produced. What is an example of a loss-of-function autosomal dominant mutation?

A

Familial hypercholesterolemia

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29
Q

Sometimes with autosomal dominant disorders you can get decreased product, dysfunctional, or inactive product produced. What is an example of a gain-of-function autosomal dominant mutation?

A

Huntington protein toxic to neurons

30
Q

There are 2 main patterns of disease that we can see with autosomal dominant mutations. What are they?

A

Regulation of complex metabolic pathways subject to feedback inhibition; key structural proteins problems

31
Q

What is an example of the autosomal dominant disease pattern that affects the regulation of complex metabolic pathways?

A

The LDL receptor in familial hypercholesterolemia

32
Q

What is an example of the autosomal dominant disease pattern that affects the key structural protein (such as collagen and cytoskeletal elements of the RBC membrane)?

A

Osteogenesis imperfecta

33
Q

What is the typical age of onset in many autosomal dominant disorders?

A

Age of onset is delayed in many autosomal dominant conditions; symptoms appear in adulthood

34
Q

What are 2 examples of autosomal recessive disorders that affect the metabolic system?

A

Cystic fibrosis and phenylketonuria

35
Q

Almost ALL inborn errors of metabolism are what?

A

Autosomal recessive

36
Q

What is the largest category of disorders?

A

Autosomal recessive

37
Q

What are 3 features of autosomal recessive disorders?

A

The trait usually does not affect the parent; siblings have a 1 in 4 chance of having the trait (25% risk each birth), if the mutation is of low frequency in population, there is a strong likelihood proband product of consanguineous marriage

38
Q

How does an autosomal recessive disorder manifest on the alleles?

A

Both alleles are affected

39
Q

How can you differentiate between autosomal recessive and autosomal dominant?

A

In autosomal recessive, the expression of the defect is more uniform than AD(everybody with the disease has a similar presentation); complete penetrance is common in AR; the onset of AR is early in life; many mutations involve enzymes in AR; new mutations in AR diseases can take generations to become evident

40
Q

The primary defect in cystic fibrosis results from abnormal function of an epithelial chloride channel protein encoded by the cystic fibrosis transmembrane conductance regulator gene on what chromosome?

A

7q31.2

41
Q

Cystic fibrosis is the most common lethal genetic disease that affects what population?

A

Caucasian populations

42
Q

What is the effect of heterozygote carriers of cystic fibrosis?

A

Although cystic fibrosis follows an autosomal recessive transmission pattern, recent data suggests that even heterozygote carriers have a higher incidence of respiratory and pancreatic diseases as compared with the general population

43
Q

What is the most common organism to colonize cystic fibrosis patients?

A

Pseudomonas aeruginosa

44
Q

What are the gastrointestinal and nutritional abnormalities seen with cystic fibrosis patients?

A

Meconium ileus and pancreatic insufficiency

45
Q

What population is PKU common in?

A

Caucasians primarily of Scandinavian descent

46
Q

What causes PKU?

A

An autosomal recessive mutation that causes a deficiency in phenylalanine hydroxylase (PAH); so phenylalanine cannot be converted into tyrosine

47
Q

How does onset of PKU present?

A

The patient is normal at birth, but as the phenylalanine accumulates, there is intellectual disability, hypopigmentation of the hair and skin, and eczema; there will also be a strong musty or mousy odor in urine and sweat

48
Q

What is an example of an X-linked recessive disorder that affects the blood?

A

Glucose-6-phosphate dehydrogenase deficiency (G6PD)

49
Q

What is an example of an X-linked recessive disorder that affects the nervous system?

A

Fragile X syndrome

50
Q

What is the inheritance pattern of X-linked recessive disorders?

A

Males are usually infertile, hence there is no Y-linked inheritance; all daughters of affected male are carriers

51
Q

What is the inheritance pattern of mitochondrial inheritance?

A

A female will pass the trait to all of her children; the male does not pass the trait on to any of their children

52
Q

What is an example of a mendelian disorder that affects an enzyme?

A

Tay-Sachs disease

53
Q

What is an example of a mendelian disorder that affects a receptor?

A

Familial hypercholesterolemia

54
Q

What is an example of a mendelian disorder that affects an ion channel?

A

Cystic fibrosis

55
Q

What are the characteristics of a Mendelian disorder?

A

There is an alteration in a single gene leading to an abnormal product or a decrease in normal product

56
Q

There are four main categories of mendelian disorders. What are they?

A

Enzyme defects, defects in receptors and transport systems, alterations in structure function or quantity of non-enzyme proteins, and mutations resulting to unusual reactions to drugs

57
Q

What are the 3 major consequences of mendelian disorders that cause enzyme defects?

A

Accumulation of the substrate, decreased amount of end product, or failure to inactivate a tissue-damaging substrate

58
Q

What is an example of a mendelian disorder that causes an enzyme defect that leads to an accumulation of substrate?

A

Galactosemia

59
Q

What is an example of a mendelian disorder that causes an enzyme defect that leads to a decreased amount of end product? (2 examples)

A

Albinism and Lesch-Nyhan

60
Q

What is an example of a mendelian disorder that causes an enzyme defect that leads to failure to inactivate a tissue-damaging substrate?

A

Alpha1-antitrypsin deficiency inability to inactivate neutrophil elastase in the lung leading to emphysema

61
Q

What should patients with alpha1-antitrypsin avoid?

A

Cigarette smoking because smoking markedly accelerate emphysema

62
Q

What mutation is associated with an alpha1-antitrypsin deficiency?

A

PiZ- homozygotes for the PiZZ protein have circulating alpha1-antitrypsin levels that are only 10% of normal

63
Q

What are PiZZ adults at risk for?

A

Hepatocellular carcinoma

64
Q

2 examples of mendelian disorders that cause alterations in structure, functions, or quantity of non-enzyme proteins?

A

Sickle cell disease and Thalassemias

65
Q

What is an example of a mendelian disorder that causes adverse reactions to drugs?

A

G6PD deficiency and the antimalarial drug primaquine this combination will cause severe hemolytic anemia

66
Q

What are 2 examples of disorders associated with defects in structural proteins?

A

Marfan syndrome and Ehlers-Danlos Syndrome

67
Q

Marfan’s syndrome is an autosomal dominant syndrome that affects what gene on what chromosome?

A

FBN1 on chromosome 15q21.1 or FBN2 on chromosome 5q23.31 (less common)

68
Q

What happens when there is a mutation in the FBN1/2 gene?

A

There is a defect in an extracellular glycoprotein called fibrillin-1

69
Q

How does loss of fibrillin lead to the clinical manifestations?

A

Either by a loss of structural support in microfibril-rich connective tissue or through excessive activation of TGF-beta signaling

70
Q

Where are microfibrils found?

A

They are abundant in the aorta, ligaments, and ciliary zonules that support the lens

71
Q

What is the specific effect of a fibrillin-2 (FBN2) mutation?

A

Congenital contractural arachnodactyly

72
Q

What happens if there is excessive activation of TGF-beta signaling?

A

Bone overgrowth and myxoid changes in mitral valves; leads to inflammation, has deleterious effects on vascular smooth muscle development, and increased activity of metalloproteases which leads to a loss of extracellular matrix

MOD Final (11 decks)

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