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SP15 Pathology > Exam 2; Genetic Disease > Flashcards

Exam 2; Genetic Disease Flashcards

1
Q

How many protein encoding genes are there in the human genome

A

roughly 19,000

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2
Q

This refers to a permanent change in the DNA

A

mutation

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3
Q

What can become of a mutation that effects germ cells

A

it can be inherited/transmitted to progeny

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4
Q

What can become of a mutation that effects somatic cells

A

can result in tumor or developmental abnormalities

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5
Q

What is a point mutation

A

a single nucleotide base substituted (missence)

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6
Q

What is a frameshift mutation

A

insertion or deletion of one or two base pairs, altering the reading frame of the DNA

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7
Q

What is a trinucleotide repeat mutation

A

amplification of sequence of 3 nucleotides (Fragile X syndrome)

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8
Q

What is a single nucleotide polymorphism

A

variation in just one nucleotide at a single site on the DNA molecule, over 6 million have been identified

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9
Q

What is a copy number variation

A

different numbers of large contiguous stretches of DNA; may account for much phenotypic variation

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10
Q

What are epigenetic changes

A

modulation of gene expression without altered DNA sequence; important in development as well as normal homeostasis

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11
Q

This of a promoter region makes them inaccessible to RNA polymerase thus reducing protein synthesis

A

methylation

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12
Q

What can occur is there are alterations in non-coding RNAs

A

microRNAs inhibit translation of their target messenger RNAs into their corresponding proteins

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13
Q

This type of disorder implies that the altered gene locus is on an autosome and the disease will be evident clinically when only one of the chromosomes in the pair exhibits a mutation at the affected gene locus

A

autosomal dominant disorder (ADD)

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14
Q

True or False

autosomal dominant disorders are evident at birth since they create outward physical changes

A

False; many exhibit delayed age onset (Huntington’s disease)

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15
Q

What is it when the person has a mutant gene (ADD) but does not express it phenotypically

A

reduce or incomplete penetrance

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16
Q

What is it when the trait is seen phenotypically in the individuals having the mutant gene but is expressed differently among the individuals (ADD)

A

variable expressivity

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17
Q

What is it when the affected individuals (ADD) may not have affected parents because their disease arose from a new mutation

A

de novo mutation

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18
Q

What are the chances of a person have (ADD) if only one parent is affected

A

50%

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19
Q

This disorder implies that the trait is expressed only in both gene at a given locus are affected (homozygous individuals)

A

autosomal recessive disorders (ARD)

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20
Q

True or False

The parents of an ARD child usually do not show the disease

A

True

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21
Q

Offspring of an heterozygous ARD carrier have what changes of having or being a carrier of the disease

A

1 in 4 chance of having it

2 in 4 (1 in 2) chance of carrying it

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22
Q

If the mutant gene is rare (ARD) there is a strong possibility that the affected child is the product of what

A

a consanguineous (from the same ancestor) relationship

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23
Q

What are three characteristics of ARD

A

two germline mutations (one from each parent) to develop the disease
equally transmitted by men and women
25% offspring; horizontal pattern in family

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24
Q

Many ARD disorders present how

A

with enzyme defects that produce inborn errors of metabolism; in heterozygous individuals, this may not be evident clinically but would have reduced numbers

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25
Q

What is the age of onset of ARD compared to ADD

A

more frequently early in life

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26
Q

The expression of the defect of ARD is what compared to ADD

A

expression is more uniform and complete penetrance is common

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27
Q

Which is more common, ARD or ADD

A

ARD

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28
Q

How many Y-linked disorders have been discovered

A

None (except the trait “hairy ears”), all sex-linked diseases are X-linked

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29
Q

Almost all X-linked disorders are this

A

recessive, therefore females are usually heterozygous

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30
Q

Who is typically affected by X-linked disorders

A

homozygous females and males (only have 1X; homozygous) i.e. hemophilia

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31
Q

What is lyonization

A

16 days after conception, all but one X-chromosome is the nucleus of each cell is inactivated; either the maternal or paternal X, all progeny will have the same inactivated X chromosome

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32
Q

What are the cell types of a lyonization female

A

a mixture; those with active paternal X and those with active maternal X; typically proportionally equal

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33
Q

This refers to inactivation of an abnormally high percentage of normal X chromosomes leading to clinical evidence of the disease in a heterozygote

A

unfavorable lyonization

34
Q

This ADD has nearly 100% penetrance, even though the gene has quite variable expressivity among the affected individuals

A

neurofibromatosis

35
Q

These disorders are inherited in a variety of patterns; mutation of genes that encode proteins necessary for formation of normal bone and connective tissue

A

diseases caused by mutations in structural proteins

36
Q

This is an ADD due to the mutation of FBN1 gene resulting in abnormal fibrillin; a glycoprotein necessary for normal elastic fiber production

A

marfan syndrome

37
Q

What is the prevalence of Marfan syndrome

A

1 in 5,000

38
Q

What are the clinical manifestations of Marfan syndrome

A 
tall, thin body 
abnormally long legs
arachnodactyly  (long fingers)
dislocation of lens of the eye
aortic aneurysm and dissection, leading to heart failure and aortic rupture
39
Q

This syndrome is highly variable (at least 6 clinical variants) and deals will a problem in collagen synthesis (30 types of collagen)

A

Ehlers-Danlos Syndrome

40
Q

What are the clinical manifestations of Ehlers-Dalos syndrome

A

hyper extensible skin and hyperbole joints
skin fragility and delayed wound healing
rupture of the colon and large arteries
hernia

41
Q

This is one of the more common inherited disorders (ADD) resulting from a mutation of the gene that encodes the LDL receptor

A

familial hypercholesterolemia

42
Q

What is the frequency of familial hypercholesterolemia

A

1 in 500

43
Q

What results from familial hypercholesterolemia

A

impaired metabolism and increased LDL cholesterol in the plasma

44
Q

What are two clinical manifestations of familial hypercholesterolemia

A

xanthomas of the skin

premature atherosclerosis

45
Q

Heterozygotes have what in regards to familial hypercholesterolemia

A

2-3x increase LDL

46
Q

Homozygotes have what in regards to familial hypercholesterolemia

A

over 5x normal LDL levels, typically die of MI by age 15/20

47
Q

This drug can be used to treat familial hypercholesterolemia

A

lomitapide

48
Q

This is an ARD that affects 1 in 10,000 caucasian infants and is caused by a lack of phenylalanine hydroxylase leading to hyperphenylalaninemia and PKU

A

phenylketouria

49
Q

What is the clinical manifestation of phenylketouria

A

affected infants are normal at birth but elevated phenylalanine levels impair brain development leading to mental retardation by 6 months

50
Q

What steps are taken to prevent phenylketouria

A

screening of newborns in mandatory in the US

restricting dietary sources of phenylalanine will prevent the development of mental retardation

51
Q

This AR transmission commonly affects infants and young children and is characterized by accumulation of insoluble large molecules (sphingolipids, mucopolysaccharides) in macrophages leading to hepatosplenomegaly

A

Lysosomal storage diseases

52
Q

What is also frequently involved with lysosomal storage diseases

A

CNS involvement, mental retardation and/or early death i.e. Tay-Sachs, Niemann-Pick, Gaucher, Mucopolysaccharidoses

53
Q

Most of these are AR traits and is due to the lack of any one of several enzymes necessary to degrade mucopolysaccharides; 7 variants

A

mucopolysaccharide storage disease

54
Q

What are the clinical manifestations of mucopolysaccharide storage diseases

A

coarse facial hair
clouding of the cornea
joint stiffness
mental retardation

55
Q

This is caused by a deficiency of alpha-L-iduronidase (laronidase); life expectancy is only 6-10 years if untreated

A

Hurler syndrome

56
Q

What are some treatment options for Hurler syndrome

A

bone marrow transplant
enzyme therapy that may improve the outlook, but not completely correct it, costs >$300,000/annually
treatment can extend the life expectancy to +/- 30 years

57
Q

This is caused by a deficiency of L-iduronate sulfatase and is in a X-linked inheritance pattern

A

Hunter syndrome

58
Q

What are the clinical manifestations of Hunter syndrome

A

coarse facial hair
joint stiffness
mental retardation
milder than Hurler syndrome

59
Q

Disorders with multifactorial inheritance has what two characteristics

A

many physiologic trains (height, weight, BP, etc.)

may underlie common diseases such as diabetes, hypertension, gout, etc.

60
Q

What characterizes a disorder with multifactorial inheritance

A

two or more genes responsible, plus environmental, non-genetic influences

61
Q

What is the frequency of inheriting a disorder with multifactorial inheritance

A

2-7%

62
Q

It is estimated that what percentage of newborns have a chromosome abnormality

A

1 in 200

63
Q

In as many as what percentage of 1st trimester spontaneous abortions, the fetus has a chromosome abnormality

A

50%

64
Q

What is a euploid

A

a normal chromosome count (2 x 23 = 46)

65
Q

What is a polyploid

A

an increase chromosome count that is a multiple of that normally seen (3 x 23 = 46) it generally results in a spontaneous abortion

66
Q

What is an aneuploidy

A

any number that is not an exact multiple of the normal chromosome, like a trisomy or monosomy

67
Q

What is a structural abnormality of a chromosome

A

chromosome breakage followed by loss or rearrangement of material

68
Q

This is a translation of a part of one chromosome to another non homologous chromosome

A

translocation

69
Q

What is reciprocal translocation

A

fragments exchanged between two chromosomes

70
Q

This is when a chromosome breaks in two points, then the released fragments are reunited after a complete turnaround

A

inversion

71
Q

This is the most common chromosomal disorder; due to meiotic non-disjunction of chromosome 21 during formation of the ovum - associated with advanced maternal age

A

trisomy 21; Down Syndrome

72
Q

What are the chances of having a child with down syndrome at 45

A

45 1:25

73
Q

What are the clinical manifestations of down syndrome

A 
mental retardation
epicanthic folds
flat facial profile
cardiac malformation
increases susceptibility to infection (periodontal disease)
large tongue
increase prevalence of acute leukemia
74
Q

This is defined as male hypogonadism that develops when there are at least two X chromosomes and one or more Y chromosomes

A

Klinefelter

75
Q

This is due to partial or complete absence of one of the X chromosomes

A

Turner syndrome

76
Q

What is the phenotype of some one with Klinefelters

A

male

77
Q

What are the clinical manifestations of Klinefelters

A 
increased length of lower limbs
reduced body hair
gynecomastia
hypogonadism
male sterility (most common cause)
78
Q

What occurs dentally involving Klinefelters

A

taurodontism (weird molars and elongated pulp chambers)

79
Q

What are the clinical manifestations of Turners syndrome

A

markedly short stature
webbing of the neck; low posterior hairline
“shield-like” chest
high arched palate
variety of congenital cardiovascular malformations
failure to develop secondary sex characteristics; primary amenorrhea (no menstruation)

80
Q

What are three ways to diagnose a genetic disease

A

FISH
comparative genetic hybridization
molecular diagnosis; PCR, restriction enzymes, comparison of the order, fluorescently labeled nucleotides

81
Q

What are four PRE-NATAL indications for genetic analysis

A

mother age >34
parent who is a carrier of a chromosomal translocation
Hx of previous child with chromosomal abnormality
parent who is a carrier of an X-linked disorder

82
Q

What are the six POST-NATAL indications for genetic analysis

A 
multiple congenital anomalies
unexplained mental retardation and/or developmental delay
suspected aneuploidy
suspected sex chromosomal abnormality
infertility
multiple spontaneous abortions

SP15 Pathology (17 decks)

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