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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
Q

what is lyonization

A

one copy of the X chromosome is inactivated
- process is random

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26
Q

what is a barr body

A

inactivated X chromosome observed in the nucleus

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27
Q

how does a barr body appear under a microscope

A

pushed off to the side of nucleus and shrunken down

28
Q

almost all sex linked disorders are ____-

A

x-linked and recessive

29
Q

describe the recessive transmission of x linked disorders

A

female carriers transmit only to sons - 50% change
- affected males do not transmit disorders to sons but all daughters are carriers

30
Q

what is the inheritance pattern, prevalence and mechanism of familial hypercholesterolemia

A
  • autosomal dominant
  • 1/500
  • loss of function mutations in gene encoding LDL receptor
  • involved in transport and metabolism of cholesterol
31
Q

what does familial hypercholesterolemia result in

A
  • elevated levels of cholesterol -> premature atherosclerosis and MI risk
  • skin xanthomas may develop
32
Q

what is the inheritance pattern, prevalance and mechanism of marfan syndrom

A
  • autosomal dominant
  • 1/5000
  • connective tissue disease
  • defect in fibrillin-1, glycoprotein in ECM
33
Q

what are the clinical features of marfan syndrome

A
  • skeletal abnormalities, slender habitus, long arms, legs and fingers
  • high arched palate
  • hyperextensibility of joints
  • ocluar changes
  • aneurysmal dilation, aortic dissection -> aortic rupture
34
Q

what is the inheritance, prevalence and mechansim of neurofibromatosis type I

A
  • autosomal dominant, type I most common
  • 1/3000
  • mutations in NFI gene, 50% represent new mutations
35
Q

what is neurofibromin

A

tumor suppressor protein

36
Q

what do patients with neurofibromatosis type I usually have

A

multiple neurofibromas

37
Q

what is a neurofibroma

A

common peripheral nerve neoplasm

38
Q

where are neurofibromas found and most common

A
  • most common on the skin
  • oral cavity: most common on tongue and buccal mucosa
39
Q

what are the clinical features of neurofibromatosis type I

A
  • 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
Q

what are the oral manifestations of neurofibromatosis type I

A
  • neurofibromas
  • enlargement of funigform papillae
  • enlargement of the mandibular canal
41
Q

what are the diagnostic criteris for neurofibromatosis

A
  • 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
Q

how do you diagnose neurofibromatosis type I on histo

A

-“shredded carrot” like appearance
- main feature is thin, wavy nuclei that are comma shaped

43
Q

what is the treatment for neurofibromatosis

A
  • manage complications
44
Q

what cancer develops from neurofibromatosis and how often

A
  • 5% of cases
  • neurofibrosarcoma
45
Q

what is the inheritance pattern prevalence and mechanism of cystic fibrosis

A
  • 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
Q

what is the dx of cystic fibrosis

A

elevated Cl- and Na+ levels in sweat

47
Q

what are the clinical feature of cystic fibrosis

A
  • 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
Q

why are males with CF infertile

A

absence of vas deferens
- no sperm in semen

49
Q

what is the tx for cystic fibrosis

A
  • antimicrobial therapies, pancreatic enzyme replacement, bilateral lung transplant
  • drugs to increase CTFR function
50
Q

what is the inheritance pattern, prevalence and mechanism of phenylketonuria (PKU)

A
  • autosomal recessive
  • 1/10,000
  • high phenylalanine levels
  • mutation in PAH gene -> lack of PAH enzyme
  • required to convert phenylalanine to tyrosine
51
Q

what are the clinical features of phenylketonuria in untreated infants

A
  • impaired brain development, developmental delays, seizures, reduced pigmentation
52
Q

how do you prevent signs and symptoms of PKU

A

regulate diet- avoid high protein food and aspartame

53
Q

what is the inheritance pattern, prevalence and mechanism of tay-sachs disease

A
  • 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
Q

what is the characteristic histopathology of tay-sachs

A
  • swollen and foamy neuron
  • swirling in neuron in EM
55
Q

what are the clinical features of tay- sachs disease

A
  • infantile form: severe, infants show signs 3-6 months of age
  • developmental impairment, seizures, blindness
  • death by 2-3 years
56
Q

what is the inheritance prevalence and mechanism of hemophilia A

A
  • x-linked
  • 1/5000
  • inherited bleeding disorder
  • factor 8 deficiency
57
Q

what are the clinical features of hemophilia A

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
Q

what is the treatment for hemophilia A

A

-replacement therapy with clotting factor
- oral or periodontal surgery - consult with physician

59
Q

what is the inheritance pattern, prevalence, and mechanism of duchenne muscular dystrophy

A
  • 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
Q

what are cytogenic disorders

A
  • result from alterations in the # or structure of chromosomes
  • may affect autosomes or sex chromosomes
  • can observe aberration on karyotype
61
Q

what is euploid

A

exact multiple of haploid cells

62
Q

what is polyploid

A

more than one pair of chromosomes
- generally results in spontaneous abortion

63
Q

what is aneuploid

A

abnormal number of chromosomes, not an exact multiple of n
- often due to nondisjunction during meisosis

64
Q

what is trisomy 21

A
  • down syndrome
  • extra copies of genes on chromosome 21
  • 95% individuals - trisomy 21
  • meitotic nondisjunction
65
Q

what are the clinical features of trisomy 21

A
  • flat facial profile
  • epicanthic folds and upward pointed eyes
  • mental retardation
  • 40% patients- congenital heart disease
  • increased leukemia risk
  • increased infections
66
Q
A

Pathology I (24 decks)

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