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Pathology > Genetic Disorders Part 2 > Flashcards

Genetic Disorders Part 2 Flashcards

1
Q

what are complex multigenic disorders

A
  • multifactorial or polygenic disorders

- variant gene + environmental factors

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2
Q

examples of complex multigenic disorders

A
  • diabetes mellitus type 2
  • congential heart disease
  • cleft lip
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3
Q

what do you exclude when diagnosing multifactoral or polygenic disorders

A
  • exclude Mendelian disorder

- exclude chromosomal mode of inheritance

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4
Q

what is a karyotype

A
  • cells in metaphase

- chromosomes are arranged in decreasing length

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5
Q

when stain is used for katyotype

A
  • Giemsa stain = G banding

- gives you light and dark bands

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6
Q

normal human chromosome #

A

46
(2n=46)
n= 23

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7
Q

what is euploid

A

2n

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8
Q

what is polyploid

A

3n

4n

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9
Q

what is aneuploid

A

not an exact number of n

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10
Q

what are cytogenetic disorders

A
  • spontaneous abortions (50% due to chromosome abnormality)

- change in # and structure of chromosomes

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11
Q

which chromosomes do cytogenetic disorders affect

A

autosomes and sex chromosomes

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12
Q

what are the types of chromosomal rearrangements

A
  1. translocation (reciprocal/ balanced. Robertsonian)
  2. deletion
  3. isochromosome
  4. inversion
  5. ring chromsome
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13
Q

what is mosaicism

A

same individual 2 or more population of cells

  • different complements of chromosomes
  • mosaicism is common in sex chromosomes
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14
Q

what are the cytogenetic disorders involving autosomes

A 
trisomy 21 (Down Syndrome)
22q11.2 Deletion Syndrome
Trisomy 18 (Edwards Syndrome)
Trisomy 13 (Patau Syndrome)
Deletion 5p (Cri du chat Syndrome)
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15
Q

karyotype of trisomy 21

A

21:47XX, +21 (95%)

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16
Q

what is the translocation type of trisomy 21

A

46XX der (14;21)(q10:q10) + 21 (4%)

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17
Q

what is the mosaic of trisomy 21

A

46XX/47XX, +21 (1%)

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18
Q

what are the 2 candidate genes for trisomy 21 (chromosome 21)

A

DYRK1A codes for a serine-threonine kinase

RCAN1 regulator of calcineurin 1

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19
Q

characteristics of Trisomy 21

A
  • epicanthic folds, flat facial profile
  • redundant neck skin; Simian crease
  • mental retardation
  • congenital heart disease (VSD, ASD)
  • acute leukemia (ALL, AML)
  • intestinal stenosis, umbilical hernia
  • Alzheimer disease
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20
Q

characteristics of Trisomy 18 (Edward Syndrome)

A
  • prominent occiput
  • mental retardation
  • micrognathia
  • clenched fist
  • IUGR (intrauterine growth retardation)
  • polyhydramnios
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21
Q

characteristics of Trisomy 13 (Patau Syndrome)

A 
Microcephaly
Mental retardation
Cleft lip
Cleft palate
Polydactyly –extra digits
Cardiac defects –mostly VSD
Renal defects
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22
Q

what is 22q11 Deletion syndrome

A

intestinal deletion: 22q11.2

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23
Q

what 2 previous diseases were 22q11 Deletion Syndrome

A 
DiGeorge syndrome
Velocardiofacial syndrome (VCFS)
24
Q

what is DiGeorge syndrome

A

T cell immunity, hypocalcemia

25
Q

what is VCFS

A

dysmorphology, cardiac defects

26
Q

22q11 Deletion Syndrome can causes

A

Schizophrenia

27
Q

what is CATCH 22

A 
Cardiac defects
Abnormal face
T cell immunity abnormal/Thymic hypoplasia
Cleft palate
Hypocalcemia
22q11 deletion
28
Q

what is Del (5p) Cri du chat

A

terminal deletion of chromosome 5

29
Q

characteristics of Del (5p) Cri du chat

A

“cat-like” cry
laryngeal hypoplasia
microcephaly
mental retardation

30
Q

what are 2 cytogenetic disorders involving sex chromosomes

A
  1. Klinefelter syndrome

2. Turner syndrome

31
Q

what is the karyotype of Klinefelter syndrome

A

XXY

32
Q

what is the mosaic pattern of Klinefelter Syndrome

A

46,XY/47, XXY, 47,XXy/48,XXXY

33
Q

Klinefelter syndrome results in

A

male hypogonadism

  • testicular atrophy
  • impaired spermatogenesis
  • reduced hair
  • low serum testosterone
34
Q

Klinefelter syndrome increases the frequency of obtaining

A

Breast cancer
SLE
Extragonadal germ cell tumor
Leydig Cell Tumor

35
Q

what are the single-gene disorders with atypical patterns of inheritance

A
  1. Triplet repeat mutations
  2. mutations in mitchondrial genes
  3. alteration of imprinted regions of genome
36
Q

name an example of triplet repeat mutations

A

Fragile X syndrome

Xq27.3

37
Q

what gene is mutated in Fragile X syndrome

A

FMR1 gene mutation

38
Q

Fragile X syndrome has an amplification of

A

CGG repeat

-amplification during oogenesis

39
Q

Fragile X syndrome

A

normal: 29 CGG
premutation: 55 to 200
Oogenesis = CGG expansion
Full mutation: greater than 200 repeats

40
Q

Fragile X syndrome: carrier males transmit

A
  • normal males
  • phenotypically normal
  • grandchildren are affected
  • at risk for FX Tremor Ataxia syndrome (FXTAS)
41
Q

Fragile X syndrome carrier females

A

30%-50% are affected

-primary ovarian failure

42
Q

Fragile X syndrome anticipation

A

manifestations worsen with successive generations

43
Q

what can cause Fragile X Syndrome

A

Neurodegenerative manifestation
Ataxia
Macroorchidism
Abnormal facial features

44
Q

how do mutations in mitochondrial genes occur

A
  1. mitochondrial DNA
    - maternal inheritance
    - transmitted to all offspring
  2. daughters transmit DNA to progeny
  3. sons do not transmit the DNA
  4. phenotypic variation
45
Q

where is mitochondrial DNA

A
  • Brian, ovary, skeletal muscles
  • oxidative phosphorylation
  • electron transport chain
46
Q

what is Leber hereditary optic atrophy (LHON)

A
  • prototype disorder
  • transmitted though mother
  • mitochondrial NADH dehydrogenase 1 (MT-ND1)
  • causes oxidative phosphorylation
  • loss of vision
47
Q

what diseases caused by alterations of imprinted genes

A
  1. Prader-Willi Syndrome

2. Angelman Syndrome

48
Q

what is genomic imprinting

A
  • an epigenetic process (not a mutation!)
  • differential inactivation
  • paternal genes
  • materal genes
49
Q

how does genomic imprinting occur

A
  • methylation of the gene promotor
  • modifications of DNA binding proteins
  • silencing of the gene
  • maternal imprinting
  • paternal imprinting
50
Q

what gene is deleted in Prader-Willi Syndrome

A

-interstitial deletion of 15q12

51
Q

Prader-Willi Syndrome affects

A

paternal chromosome

52
Q

characteristics of Prader-Willi Syndrome

A

short stature, small hands, feet; hypogonadism

53
Q

what gene is deleted in Angelman Syndrome

A

interstitial deletion of 15q12

54
Q

what happens to the maternal chromosome in Angelman Synrome

A

maternal chromosome is silenced

55
Q

characteristics of Angelman Syndrome

A

-mental retardation, ataxia, inappropriate laughter

56
Q

what is the Angelman gene

A

-maternally derived

UBE3A - a ligase in ubiquitin-proteosom proteolytic pathway

Pathology (18 decks)

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