Down Syndrome and Other Abnormalities of Chromosome Number Flashcards
Abnormal cells that do not contain a multiple of haploid number of chromosomes
Aneuploid cells
Most common and clinically significant type of human chromosome abnormality
Aneuploidy
MC cause of aneuploidy
Nondisjunction
Characeterized by the presence of 3 chromosomes
Trisomy
MC form of aneuploidy
Trisomy
Technique used for rapid diagnosis in the prenatal detection of common fetal aneuploidies
FISH
MC numerical abnormalities in live born children (3)
1) T21 Down’s 2) T18 Edwards 3) T13 Patau
MC type of trisomy in liveborn infants
Trisomy 21
T/F The occurrence of Trisomy 21 and other trisomies increased with advanced age
T
Age at which occurrence of Trisomy increases
> 35 y/o
___% of spontaneous abortuses have chromosomal abnormalities
50%
MC chromosomal abnormality in abortuses
45,X (Turner)
___% of 45,X are foetuses are spontaneously aborted
99
Features in NB and children that suggest the presence of a chromosome anomaly
1) LBW/SGA 2) Failure to thrive 3) Developmental delay 4) 3 or more congenital malformations
MC genetic cause of moderate mental retardation
Down syndrome
T/F Individuals affected with Down syndrome are more prone to CHD
T
A complication of Down syndrome that occurs as early as the 4th decade
Alzheimer disease-like dementia
T/F Developmental delay is universal in individuals with Down syndrome
T
Area of development that is relatively spared in Down syndrome
Social development
All women should be offered screening for Down syndrome when
2nd trimester
Maternal serum tests used to screen Down Syndrome (4)
1) Free beta HCG 2) Unconjugated estriol 3) Inhibin 4) alpha fetoprotein
The origin of supernumerary chrome 21 in children with Down syndrome is
Maternal (97%)
Fusions in Down syndrome, found at the centromere between chromosomes 13, 14, 15, 21, and 22
Robertsonian translocations
MC abnormality of chromosomal number
Trisomy 21
Nondysjunctional event in Down syndrome pregnancy occurs during
Maternal meiosis phase I
T/F In approx 95% of cases of Down Syndrome, there are 3 copies of chromosome 21
T
