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Kaplan Biochem and Genetics > Cytogenetics and Common Diseases > Flashcards

Cytogenetics and Common Diseases Flashcards

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Biology 101 flashcards
1
Q

Chromosome abnormalities = leading known cause of pregnancy loss

  • ___% of spontaneous fetal losses in 1st T
  • ___% of spontaneous fetal losses in 2nd T
A
  • 50% of spontaneous fetal losses in 1st T
  • 20% of spontaneous fetal losses in 1st T
  • trisomy = MC genetic cause of spontaneous abortion
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2
Q

long arm =

A
  • long arm = q

- short arm = p “petite”

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3
Q

Karyotypes are arranged from the ____ chromosome to the ____ chromosome

A

arranged longest to shortest

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4
Q

Acrocentric chromosomes

A
  • have the centromere far toward one end
  • the p arm contains little info
  • 13-15, 21-22
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5
Q

Triploid

A
  • 69 chromosomes
  • when 2 sperm fertilize one egg at once
  • common at conception, most lost prenatally. 1/10000 births
  • lethal: multiple heart and CNS defects
  • Tetraploid = 1 egg is fertilized by 3 sperm (92 chromosomes); extremely rare, lethal
  • examples of euploid (when a cell has a multiple of 23 Ch)
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6
Q

Down Syndrome

A
  • Trisomy 21; MC autosomal trisomy
  • mental retardation
  • short stature
  • hypotonia
  • depressed nasal bridge, upslanting palpebral fissures, epicanthal fold
  • congenital heart defect (endocardial cushion defect) in approx 40%
  • increased risk of acute lymphoblastic leukemia
  • Alzheimers in 50-60s (amyloid precursor protein, APP gene on Ch 21)
  • reduced fertility
  • risk increases with AMA
  • if caused by nondisjunction during meiosis, not associated with prior pregnancy loss
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7
Q

Edward Syndrome

A
  • Trisomy 18
  • inward turning, rocker-bottom feet (prominent heels)
  • clenched first w overlapping fingers
  • congenital heart defects
  • low-set ears, micrognathia (small lower jaw)
  • mental retardation
  • poor prognosis
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8
Q

Patau Syndrome

A
  • Trisomy 13
  • polydactyly (extra fingers and toes)
  • cleft lip, palate
  • microphthalmia, mental retardation
  • cardiac and renal defects
  • very poor prognosis
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9
Q

Klinefelter Syndrome

A
  • 47, XXY (Always male bc Y has testes determining factor)
  • testicular atrophy (maybe undescended testicles)
  • infertility
  • gynecomastia
  • female distribution of hair
  • low testosterone
  • elevated FSH and LH
  • high-pitched voice
  • no mental retardation
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10
Q

Turner Syndrome

A
  • 45, X (50%) or 45, XO
  • only monosomy consistent with life
  • majority of others are mosaics for 45,X and one other cell lineage (46,XX ; 47,XXX, 46,XY)
  • females with 45,X or 46,XY are at an increased risk for gonadal blastoma
  • short stature
  • edema of wrists and ankles in newborn
  • cystic hygroma in utero resulting in excess nuchal skin and webbed neck
  • primary amenorrhea (never menstruate)
  • coarctation of aorta or other central heart defect in some cases
  • infertility
  • gonadal dysgenesis
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11
Q

Nondisjunction is MC in

A
  • 70% of nondisjunction occurs in meiosis I in females
  • MC in oogenesis than spermatogenesis
  • MC with AMA (bc a woman’s eggs are formed during fetal development and remain in prophase I until ovulation)
  • nondisjunction is the usual case of aneuploidies including Down, Edward, Patau, Turner and Klinefelter
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12
Q

Assay for Down Syndrome (can detect 70% of fetuses with Down)

A

serum levels of:

  • alpha-fetoprotein
  • chorionic gonadotropin
  • unconjugated estriol
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13
Q

Reciprocal translocation

A
  • when genetic material is exchanged btw non-homologous chromosomes (i.e. btw Ch 2 and 8)
  • happens during gametogenesis
  • offspring will carry the reciprocal translocation in ALL their cells = translocation carrier
  • Karyotype if btw short arms of Ch 2 and 8 in male: 46XY,t(2p;8p)
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14
Q

t(9;22)

A

chronic myelogenous leukemia (c-abl)

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15
Q

t(15;17)

A

acute myelogenous leukemia (retinoid receptor-alpha)

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16
Q

t(14;18)

A

follicular lymphoma (bcl-2 that inhibits apoptosis)

17
Q

t(8;14)

A

Burkitt lymphoma (c-myc)

18
Q

t(11;14)

A

mantle cell lymphoma (cyclin D)

19
Q

Robertsonian Translocation

A
  • responsible for 5% of Down Syndrome cases
  • MC than reciprocal translocations
  • occur only in acrocentric chromosomes (13-15; 21-22)
  • involve the loss of the short arms of 2 of the chromosomes and subsequent fusion of the long arms
  • suspect in young mother with previous miscarriages
  • adjacent segregation produces unbalanced genetic material and most likely loss of pregnancy. Exception: Downs
  • alternate segregation produces a normal haploid gamete (and diploid conception) OR a liveborn who is phenotypically normal translocation carrier
20
Q

Wilms Tumor Sx

A 
W: Wilms Tumor
A: aniridia
G: genital abnormalities
R: mental retardation
- result of micro deletion that includes several contiguous genes
21
Q

Williams Syndrome Sx

A
  • hypercalcemia
  • supravalvular aortic stenosis
  • mental retardation
  • characteristic facies
  • result of micro deletion that includes several contiguous genes
22
Q

DiGeorge Syndrome Sx

A
  • congenital absence of thymus and parathyroids
  • hypocalcemic tetany
  • T-cell immunodeficiency
  • characteristic facies (cleft palate)
  • heart defects
  • result of micro deletion that includes several contiguous genes
23
Q

oncogenes generally encode proteins that

A
  • stimulate the cell cycle
  • the abnormal alleles encode proteins that are more active than normal proteins
  • gain of function; one hit
24
Q

tumor suppressor genes generally encode proteins that

A
  • inhibit the cell cycle or
  • participate in DNA repair processes
  • abnormal alleles could either produce no protein product = null alleles
  • or encode proteins with significantly reduced activity
  • loss of function; 2 hits
25
Q

gene involved in coronary heart disease

A
  • LDL receptor gene (apoB-100 receptor gene)
26
Q

gene involved in hereditary nonpolyposis colorectal cancer (HNPCC); lynch syndrome

A
  • hMLH1, hMLH2 genes encoding mismatch repair genes
27
Q

gene involved in adenomatous polyposis colorectal cancer

A
  • APC gene encoding cell adhesion/nuclear signaling protein
28
Q

gene involved in breast cancer

A
  • p53 encodes a protein that halts the cell cycle for DNA repair
  • Familial only: BRCA 1, BRCA 2
29
Q

gene involved in Alzheimer disease

A
  • Familial only: BAPP (beta amyloid precursor protein: 21q21)
  • Familial only: Presenilin (improper processing of beta-amyloid precursor protein
  • sporadic, late-onset: APOE (epsilon4 allele) encoding a variant of ApoE
30
Q

gene involved in Diabetes

A
  • MODY: high heritability, HNF genes, GLK (glucokinase gene)
  • IDDM (Ty1): Moderate heritability w linkage to HLA-D (DR3/4) with HLA-DQ (beta) most likely locus. Other non-MHC loci involved
  • NIDDN (Ty2): high heritability, multiple susceptibility loci

Kaplan Biochem and Genetics (21 decks)

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