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Table.1 Karyotype analysis
karyotype No. % Mean maternal age
1. Free trisomy 21 82
M :F=1.1 :1
47,XY,+21 43
71.93% 33.43
47,XX,+21 39
2. Translocation
11
46,XY,der(21;21)(q10;q10),+21
M:F=1.2:1
46,XX,der(21;21)(q10;q10),+21
3
9.65% 26.54
46,XY,der(14;21)(q10;q10),+21
3
46,XX,der(14;21)(q10;q10),+21
3
2
Vasilica Plaiaşu
1
, Gabriela Motei
1
, Florina Nedelea
2
, Elena Neagu
3
, Amalia Costin
1
3. Mosaics 3
1 Department of Medical Genetics, IOMC “Prof Dr Alfred Rusescu”, Bucharest
M:F=2:1
2 Materno-Fetal Medical Department - Clinical Hospital “Filantropia”, Bucharest
mos47,XY,+21[36]/46,XY[14] 1 2.63% 34.66
3 DNA Laboratory - National Legal Medicine Institute “Mina Minovici”, Bucharest
mos47,XY,+21[34]/46,XY[16] 1
mos46,XX,der(21;21)(q10;q10)[87]/46,XX,del21p[13] 1
4. Wihout karyotype
18
M:F=1:1.25
1.79% 30.25
TOTAL 114
produced with an extra copy of chro- tailed information was collected from
mosome 21; the gamete thus has 24 the patients and their families from di-
chromosomes. When combined with a fferent regions of the country.
normal gamete from the other parent, Chromosomal analysis was perfor-
the embryo has 47 chromosomes, with med using standard protocols. Hepari-
three copies of chromosome 21.[3] nized whole blood samples were set up
b. Mosaicism is the cause of 2–4% in nutrient media. The cultures were
of the observed Down syndromes and stimulated with phytohaemagglutinin
can arise by postzygotic (mitotic) non- and incubated for 72h at 37°C. The
disjunction of a normal zygote or the cultures were arrested with colchici-
postzygotic loss of a chromosome 21 ne and treated with KCl. The cultures
Fig.1 Karyotype of a girl with Down
from a trisomic zygote. In these cases were fixed with fixative (methanol :
syndrome – Trisomy 21
people have a mixture of cells (cell li- acetic acid = 3:1). The chromosomes
nes): some cells have a normal set of were prepared on slides and were on). They were referred between the
chromosomes, and other cells have subjected to GTG-banding. The slides periods January 2007 – June 2008 to
trisomy 21. [4] were treated with trypsin in buffer and Genetics Department to confirm the
c. Robertsonian translocation is the stained with Giemsa stain. clinical diagnosis of Down syndrome.
cause of 1–2% of observed cases of At least 30-well spread and banded The birth frequency of DS babies in
Down syndrome. In this case, the long metaphases were analyzed under mi- younger mother (<35 years) was 67.89
arm of chromosome 21 is attached to croscope in each case and 5 cells ka- % compared to older mother (>35
another chromosome, often chromo- ryotyped. In cases of mosaicism, 50 years) with 32.11 %.
some 14 or itself. metaphases were scored. Parents of Cytogenetic analysis of 96 cases of
d. Duplication of a portion of chro- children having robertsonian trans- Down syndrome is presented in Table
mosome 21 is very rare. This means location were investigated to rule out 1. There were 82 cases of free trisomy
that there are extra copies of some, the origin of altered chromosome. (71.93%), 11 cases with translocation
but not all, of the genes on chromoso- The karyotypes were interpreted (9.65%) and 3 cases
me 21. according to the recommendations of had mosaicism ( 2.63 %). Male to fe-
ISCN 2005 (an International System for male ratio in patients of DS with free
Material and method Human Cytogenetic Nomenclature). trisomy 21 was 1.1:1 and that of trans-
The present study was undertaken location was 1.2:1. Translocation in
in referred Down syndrome cases. 114 Results and discussion Down syndrome is usually of Robert-
patients attending Genetics Depart- The retrospective study included sonian type with the fusion of chromo-
ment of IOMC “Prof Dr Alfred Rusescu” 114 children in the age range of 6 days some 21 to D or G group chromosomes.
were included in the present study. De- to 10 years (at the time of examinati- The forms are t( 21;21) and t(14;21).
Vol. 4, Nr. 3/septembrie 2008
pag. 171
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