CYTOGENETIC PRACTICE I
NO. 435- COURSE: HEREDITY
Key words:
congenital and acquired chromosomal aberrations, abnormalities
of chromosomal number, structural chromosome rearrangements
balanced and unbalanced, partial monosomy, partial trisomy,
terminal and intersticial deletions, duplication, reciprocal
translocation, Robertsonian translocation, inversion pericentric
and paracentric, insertion, dicentric chromosome, ring
chromosome, marker chromosome (structuraly abnormal extra
chromosome), isochromosome, derivative chromosome,
recombinant chromosome, unequal crossing over, meiotic
recombination, double minutes, homogeneously staining regions
(HSRs), Philadelphia chromosome (Ph1), microdeletion
(contiguous gene) syndromes, chromosome instability syndromes,
ovarian teratoma, hydatiform mole, prenatal and postnatal
cytogenetic examination, amniocentesis (AMC), chorionic villus
sampling (CVS), cordocentesis.
Review of some cytogenetic abbreviations and symbols
(according ISCN -International System for Human Cytogenetic
Nomenclature)
p
short arm
q
long arm
cen
centromere
h
heterochromatin
s
satellite
ter
terminal end of arm
del
deletion
dup
duplication
t
translocation
inv
inversion
i
isochromozome
ins
insertion
r
ring chromosome
dic
dicentric chromosome
mar marker chromosome
mat
maternal origin
pat
paternal origin
der
derivative chromosome
rec
recombinant chromosome
:
break and loss of a part of chromosome distal to break
::
break and reunion (in detailed description)
+
before number of chromosome = trisomy
-
before number of chromosome = loss of chromosome, monosomy
/
for separations of different cell lines in mosaic
p12
site of break on the short arm (according scheme of G banding)
q13
site of break on the long arm (according scheme of G banding)
1. Describe types of aberrations. Which karyotypes will be probably connected with
normal phenotype?
45,XX,der(14;21)(q10;q10)
46,XX,der(14;21)(q10;q10),+21
45,XX,der(21;21)(q10;q10)
46,XX,der(21;21)(q10;q10),+21
46,XY,inv(3)(q21q26)
46,XX,inv(2)(p21q31)
46,XX,rec(2)dup(2p)inv(2)(p21q31)
46,XX,rec(2)dup(2q)inv(2)(p21q31)
46,XX,dup(1)(q22q25)
46,XX,dup(1)(q25q22)
46,XX,ins (5;2)(p14;q22q32)
46,XY,del(5)(p13)
46,XY,del(5)(q15q22)
46,X,i(X)(q10)
46,XX,i(17)(q10)
46,XX,r(9)(p24q34)
46,XX,t(2;18)(p13;q21)
46,XY,der(18)t(2;18)(p13;q21)mat
46,XY,der(2)t(2;18)(p13;q21)mat
45,X[10]/47,XXX[10]/46,XX[30]
46,XX/46,XY
47,XY,+mar
47,XX,+21/46,XX
2. Describe possible origin of karyotype 49,XXXXX?
3. The woman has hemophilia and cytogenetic examination is
recommended. Why? (This woman is not daughter of
hemophilic man and woman carrier of hemophilia).
4. Explain karyotype 46,XX in male phenotype?
5. A baby girl has testes in the inguinal canals. What is her disorder? What
karyotype would you expect to find in the child?
6. A child with ambiguous genitalia is found to have 21- hydroxylase
deficiency.What karyotype woud you expect to find in the child?
7. A newborn girl has lymphoedema on feet. Why the cytogenetic
analysis is recommended?
8. A woman – carrier of balanced translocation 14/21 - has a child
with Down syndrome. What is the risk of Down syndrome for
another child a) theoretic risk, b) real risk?
9. A woman – carrier of balanced translocation 21/21 - has a child
with Down syndrome. What is the risk of Down syndrome for
another child a) theoretic risk, b) real risk?
10. Parents of a child with translocation form of Down syndrome
have both normal karyotypes. What is the risk of the same
abnormality for the next pregnancy?
11. In what case and what type of cytogenetic analysis is recommended?
• 29 year-old pregnant woman with 41 year-old husband
• 39 year-old pregnant woman with 29 year-old husband
• 20 year-old pregnant woman with 53 year-old husband
• 30 year-old pregnant woman who has had previous child with free
trisomy 21
• 30 year-old pregnant woman who has had previous child with karyotype
46,XX,der(14;21)(q10;q10),+21
• 30 year-old pregnant woman who has had previous child with karyotype
46,XY,der(21;21)(q10;q10),+21
• 30 year-old pregnant woman who has had previous child with karyotype
45,XY,der(14;21)(q10;q10)
• 30 year-old pregnant woman who has had previous child with karyotype 45,X
• 30 year-old pregnant woman who has had previous child with karyotype
46,X,i(Xq)
• 30 year-old pregnant woman who has had previous child with karyotype
46,XY, del(6)(p13)
• 30 year-old pregnant woman who has had three spontaneous abortions
• husband of woman who has had three spontaneous abortions
12. Compare the advantages and disadvantages of amniocentesis
(AMC) and chorionic villus sampling (CVS).
13. Prenatal cytogenetic examination at 10 weeks´ gestation reveal
more chromosome abnormalities than those obtained in at
16 weeks´gestation. Explain this situation.
14. What are the indications for postnatal and prenatal cytogenetic
analysis ?
15. What is the difference in triploid product of fertilisation arising by
fusion of a) haploid ovum and diploid sperm, b) diploid ovum
and haploid sperm, c) arising by dispermy?
16. What is the reason of origin of a) numerical, b) structural
chromosomal aberrations?
17.Why we cannot detect all trisomies in newborns? Can you see
autosomal monosomies in newborns? If not, why?
18. Can you describe cytogenetic manifestation of fragile X and
condition of fragile X manifestation in cultivated cells?
19. Explain why the same deletion on chromosome 15 can lead in one
case to Prader Willi and in other case to Angelman syndrome?
Karyotype assembly
from photograph