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Pathology I > Principles of Genetic Disease > Flashcards

Principles of Genetic Disease Flashcards

1
Q

what is a gene

A

hereditary factor that determines a particular trait

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2
Q

what is an allele

A

a variety of a gene
- ex: heterozygous or homozygous

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3
Q

what is a chromosome

A

a structure made up of proteins and DNA and organized into genes

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4
Q

what is a genotype

A

the genetic makeup of an individual consisting of the genes on all 46 chromosomes

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5
Q

what is a phenotype

A

observable characteristics or traits of an individual resulting from the genotype

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6
Q

what is autosomal dominant

A

one variant of a gene on a chromosome overrides the effect of a different variant of the same

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7
Q

what is autosomal recessive

A

two copies of an abnormal gene must be present for the disease or trait to develop

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8
Q

what is a karyotype

A

an individuals complete set of chromosomes

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9
Q

how are chromosomes arranged

A

according to size and banding patterns

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10
Q

what is homozygous

A

same version of a gene is inherited from each parent

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11
Q

what is heterozygous

A

different version of a gene is inherited from each parent

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12
Q

what is haploid

A

single set of chromosomes in an organism

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13
Q

what is diploid

A

two copies of each chromosome

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14
Q

what are hereditary disorders

A

familial inheritance transmitted through generations

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15
Q

what are congenital disorders

A

disorders present at birth

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16
Q

what do mendelian disorders result from

A

result from mutations in single genesw

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17
Q

what do complex disorders involve

A

multiple genes, including environmental influence

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18
Q

what are chromosomal abnormalities

A

change in number or structure of chromosomes

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19
Q

describe mendelian disorders

A

-single gene hereditary mutations
- wide range of phenotypic effects
- mutated gene can be influenced by modifier genes

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20
Q

what are the 3 patterns of inheritance in mendelian disorders

A
  • autosomal dominant
  • autosomal recessive
  • X-linked
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21
Q

describe autosomal dominant inheritance

A
  • usually one parent is affected, not sex dependent
  • may occur due to new mutations within the sperm or egg
  • clinical features modified by reduced penetrance and variable expressivity
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22
Q

what is the age of onset with autosomal dominant inhertiance diseases

A

may be delayed from childhood

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23
Q

describe autosomal recessive inheritance

A
  • homozygous
  • both parents are carriers
  • complete penetrance is common
  • new mutations rarely detected clinically
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24
Q

what is the age of onset with autosomal recessive inheritance diseases

A

usually early in life

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25
what is lyonization
one copy of the X chromosome is inactivated - process is random
26
what is a barr body
inactivated X chromosome observed in the nucleus
27
how does a barr body appear under a microscope
pushed off to the side of nucleus and shrunken down
28
almost all sex linked disorders are ____-
x-linked and recessive
29
describe the recessive transmission of x linked disorders
female carriers transmit only to sons - 50% change - affected males do not transmit disorders to sons but all daughters are carriers
30
what is the inheritance pattern, prevalence and mechanism of familial hypercholesterolemia
- autosomal dominant - 1/500 - loss of function mutations in gene encoding LDL receptor - involved in transport and metabolism of cholesterol
31
what does familial hypercholesterolemia result in
- elevated levels of cholesterol -> premature atherosclerosis and MI risk - skin xanthomas may develop
32
what is the inheritance pattern, prevalance and mechanism of marfan syndrom
- autosomal dominant - 1/5000 - connective tissue disease - defect in fibrillin-1, glycoprotein in ECM
33
what are the clinical features of marfan syndrome
- skeletal abnormalities, slender habitus, long arms, legs and fingers - high arched palate - hyperextensibility of joints - ocluar changes - aneurysmal dilation, aortic dissection -> aortic rupture
34
what is the inheritance, prevalence and mechansim of neurofibromatosis type I
- autosomal dominant, type I most common - 1/3000 - mutations in NFI gene, 50% represent new mutations
35
what is neurofibromin
tumor suppressor protein
36
what do patients with neurofibromatosis type I usually have
multiple neurofibromas
37
what is a neurofibroma
common peripheral nerve neoplasm
38
where are neurofibromas found and most common
- most common on the skin - oral cavity: most common on tongue and buccal mucosa
39
what are the clinical features of neurofibromatosis type I
- multiple neurofibromas - vary in size, small papules to large masses (elephantiasis neuromatosa) the skin - few tumors to hundreds or thousands - cafe au lait macules on skin - 2/3 have relatively mild disease
40
what are the oral manifestations of neurofibromatosis type I
- neurofibromas - enlargement of funigform papillae - enlargement of the mandibular canal
41
what are the diagnostic criteris for neurofibromatosis
- patient must have at least 2 of these features: - six or more cafe au lait macules greater than 5mm in prepubertal persons or more than 15mm in postpubertal persons - two or more neurofibromas of any type or one plexiform neurofibroma - freckling in the axillary or inguinal regions - optic glioma - two or more lisch nodules - a distinctive osseous lesion - a first degree relative with NF1
42
how do you diagnose neurofibromatosis type I on histo
-"shredded carrot" like appearance - main feature is thin, wavy nuclei that are comma shaped
43
what is the treatment for neurofibromatosis
- manage complications
44
what cancer develops from neurofibromatosis and how often
- 5% of cases - neurofibrosarcoma
45
what is the inheritance pattern prevalence and mechanism of cystic fibrosis
- autosomal recessive - 1/2500 - disorder affecting ion transport - abnormal fluid secretion in exocrine glands - affects respiratory, gastrointestinal and reproductive tract - mutation in CTFR gene: abnormal function of chloride channel regulator protein
46
what is the dx of cystic fibrosis
elevated Cl- and Na+ levels in sweat
47
what are the clinical feature of cystic fibrosis
- viscous mucus secretions- block airway and the pancreatic ducts - recurrent pulmonary infections and pancreatic insufficiency - high NaCl level in sweat - sinusitis - liver cirrhosis - male infertility
48
why are males with CF infertile
absence of vas deferens - no sperm in semen
49
what is the tx for cystic fibrosis
- antimicrobial therapies, pancreatic enzyme replacement, bilateral lung transplant - drugs to increase CTFR function
50
what is the inheritance pattern, prevalence and mechanism of phenylketonuria (PKU)
- autosomal recessive - 1/10,000 - high phenylalanine levels - mutation in PAH gene -> lack of PAH enzyme - required to convert phenylalanine to tyrosine
51
what are the clinical features of phenylketonuria in untreated infants
- impaired brain development, developmental delays, seizures, reduced pigmentation
52
how do you prevent signs and symptoms of PKU
regulate diet- avoid high protein food and aspartame
53
what is the inheritance pattern, prevalence and mechanism of tay-sachs disease
- autosomal recessive - 1/3500 - lysosomal storage disease - mutations in hexoaminidase A -> accumulation of gangliosides - primarily affects neurons and retina - accumulates in other tissues: heart, liver and spleen
54
what is the characteristic histopathology of tay-sachs
- swollen and foamy neuron - swirling in neuron in EM
55
what are the clinical features of tay- sachs disease
- infantile form: severe, infants show signs 3-6 months of age - developmental impairment, seizures, blindness - death by 2-3 years
56
what is the inheritance prevalence and mechanism of hemophilia A
- x-linked - 1/5000 - inherited bleeding disorder - factor 8 deficiency
57
what are the clinical features of hemophilia A
- failure of hemostasis after circumcision- common first sign - significant hemorrhage after minor trauma - hemarthrosis- may result crippling deformity of joints - increased coagulation time
58
what is the treatment for hemophilia A
-replacement therapy with clotting factor - oral or periodontal surgery - consult with physician
59
what is the inheritance pattern, prevalence, and mechanism of duchenne muscular dystrophy
- X-linked - Skeletal muscle defects - 1/3500 males - mutation in dystrophin gene-> defects in dystrophin protein - found in skeletal, cardiac, brain and peripheral nerves - muscle weakness - cardiac muscle damage -> arrythmias and heart failure - cognitive impairment
60
what are cytogenic disorders
- result from alterations in the # or structure of chromosomes - may affect autosomes or sex chromosomes - can observe aberration on karyotype
61
what is euploid
exact multiple of haploid cells
62
what is polyploid
more than one pair of chromosomes - generally results in spontaneous abortion
63
what is aneuploid
abnormal number of chromosomes, not an exact multiple of n - often due to nondisjunction during meisosis
64
what is trisomy 21
- down syndrome - extra copies of genes on chromosome 21 - 95% individuals - trisomy 21 - meitotic nondisjunction
65
what are the clinical features of trisomy 21
- flat facial profile - epicanthic folds and upward pointed eyes - mental retardation - 40% patients- congenital heart disease - increased leukemia risk - increased infections
66

Pathology I (24 decks)

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