chromosomal numerical aberrations
TRANSCRIPT
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CHROMOSOMAL CHROMOSOMAL NUMERICAL NUMERICAL
ABERRATIONSABERRATIONSINSTITUTE OF BIOLOGY AND MEDICAL
GENETICS OF THE 1ST FACULTY OF MEDICINE
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CHROMOSOMAL ABERRATIONSCHROMOSOMAL ABERRATIONS
►► NUMERICALNUMERICAL
►► STRUCTURALSTRUCTURAL
►► MIXOPLOIDYMIXOPLOIDY
POLYPLOIDY
• MOSAICISM• CHIMERISM
ANEUPLOIDY
TRIPLOIDYTETRAPLOIDY
MONOSOMYTRISOMY
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LIST OF BASIC SYNDROMESLIST OF BASIC SYNDROMES
NUMERIC ANOMALIESNUMERIC ANOMALIESOF AUTOSOMES:OF AUTOSOMES:DOWN SYNDROME
47,XX/Y,+21PATAU SYNDROME
47,XX/Y,+13EDWARDS SYNDROME 47,XX/Y,+18
NUMERIC ANOMALIESNUMERIC ANOMALIESOF SEXOF SEXCHROMOSOMES:CHROMOSOMES:TURNER SYNDROME 45,XKLINEFELTER SYNDROME
47,XXYXYY SYNDROME (SUPERMALE) 47,XYYXXX SYNDROME (SUPERFEMALE) 47,XXX
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DOWN SYNDROMEDOWN SYNDROME1 : 600 - 8001 : 600 - 800
• hypotonia in newborns• upslanting palpebral
fissures• neck webbing• dysplasia of ears• flat occiput• single palmar crease• epicantic folds (inner
canthus) • congenital heart
defects, defects of other organs
EPICANTHUS
TRISOMY 21 NORMAL
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DOWN SYNDROMEDOWN SYNDROME
• mental retardation• macroglossia• male hypogenitalism• denture defects• short, broad hands,
brachydactyly• immune system
defects• higher risk of
tumour diseases (leukemia)
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DOWN SYNDROMEDOWN SYNDROMEDENTAL ABNORMALITIESDENTAL ABNORMALITIES
• hypodontia – lateral incisors upper and lower, second premolars upper and lower
• changes in tooth size and shape (both permanent and deciduous dentition) – size reduction,
shovel-shaped incisors, reduced root lenghts
• increased risk of periodontal disease
• reduced caries prevalence
• underdevelopment of the upper jaw
• delayed eruption of teeth
• third molar agenesis, more often in the maxilla
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PATAU SYNDROMEPATAU SYNDROME1 : 15 000 – 20 0001 : 15 000 – 20 000
• severe developmental retardation
• congenital heart defects
• microcephaly• malformed, low-set
ears• microphtalmia• polydactyly• kidney anomalies • cleft palate, cleft lip
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PATAPATAUU SYNDROM SYNDROMEE
cleft palate, cleft lip
cyclopia
polydactyly
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EDWARDS SYNDROMEDWARDS SYNDROMEE1 : 5 000 - 10 0001 : 5 000 - 10 000
• severe developmental retardation
• heart defects• malformed, low-set ears• hypoplastic nails• digits overlapping• micrognathia• prominent occiput• pedes equinovares (clubfoot)• microcephaly
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EDWARDS SYNDROMEDWARDS SYNDROMEEpedes equinovares
malformed, low-set ears
digits overlappingmicrognathia
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TURNER SYNDROMTURNER SYNDROMEE1 : 2 000 – 2 5001 : 2 000 – 2 500
• short stature – hormonal therapy
• gonadal dysgenesis, primary amenorrhoea
• average intelligence• short webbed neck
(pterygium colli)• low posterior hairline• broad/shield chest• palms and feet edema
(newborns)PTERYGIUM COLLI
BROWNNEVI
RUDIMENTARYOVARIES
18 YEARS
SHORTSTATURE WEBBED NECK
SHIELD CHESTUNDERDEVELOPED
BREASTS
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TURNER SYNDROMETURNER SYNDROME
DENTAL ABNORMALITIESDENTAL ABNORMALITIES
• premature eruption of permanent teeth
• root resorption
• changed palate morphology – high arched palate
• malocclusion
Hygroma colli cysticum Hygroma colli cysticum (aborted fetus)(aborted fetus)
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KLINEFELTER SYNDROMKLINEFELTER SYNDROMEE1 : 500 - 1 0001 : 500 - 1 000
• tall stature• average intelligence• male psychosexual
orientation• hypoplastic testes,
cryptorchism• sterility -
azoospermia• gynaecomastia
FEMALE PUBICFEMALE PUBICHAIR PATTERNHAIR PATTERNTESTICULARTESTICULAR
ATROPHYATROPHY
POOR BEARDPOOR BEARDGROWTHGROWTH
GYNGYNAECAECOMASTIOMASTIAA
TALLTALLSTATURESTATURE
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KLINEFELTER SYNDROMEKLINEFELTER SYNDROME DENTAL ABNORMALITIESDENTAL ABNORMALITIES
• taurodontism of molars (enlarged pulp chamber and lengthened crown)
• shovel-shaped incisors
NORMAL TAURODONTISM
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XXX XXX SYNDROMSYNDROMEE (SUPERFEMALE) (SUPERFEMALE)
• 1 : 1000, no specific phenotype• average intelligence• normal sexual development• decreased fertility (spontaneous abortions), without risk of chromosomal aberrations in offspring• no increased occurrence of congenital disorders over to population risk
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XYY XYY SYNDROMSYNDROMEE (SUPERMALE) (SUPERMALE)
• „robust“ growth (proportional), especially height • average intelligence• normal sexual development• normal fertility, without risk of chromosomal aberrations in offspring• controversy - affected psychosocial development
TWINS – TALLER 47,XYY
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task 7, p. 81
Enumerate the Barr bodies in:
a) 45,Xb) 48,XXXXc) 47,XXYd) 49,XXXXXe) 47,XYYf) 46,XXg) 47,XX,+21h) 48,XXXYi) 47,XY,+13
a) 0b) 3c) 1d) 4e) 0f) 1g) 1h) 2i) 0
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NONDISJUNCNONDISJUNCTIONTION
NORMAL NONDIS. MI NONDIS. MII
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aberrant gamete
Fill in the scheme of the nondisjunction in meiosis I in mother leading to the birth
of a child with Klinefelter syndrome
zygote
II. parent
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–
––
Fill in the scheme of the nondisjunction in meiosis I in mother leading to the birth
of a child with Klinefelter syndrome aberrant gamete II. parent
zygote
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aberrant gamete
Fill in the scheme of the nondisjunction in meiosis II in father leading to the
birth of a child with Turner syndrome
zygote
II. parent
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–
–
Fill in the scheme of the nondisjunction in meiosis II in father leading to the
birth of a child with Turner syndrome aberrant gamete II. parent
zygote
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aberrant gamete
Fill in the scheme of the nondisjunction in meiosis I in one parent leading to the birth of a child with Down syndrome
zygote
II. parent
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aberrant gamete
Fill in the scheme of the nondisjunction in meiosis I in one parent leading to the birth of a child with Down syndrome
zygote
II. parent
–
– –
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aberrant gamete
task 12, p.86: A colour-blind mother and father with normal colour vision have a son with normal vision whose karyotype is 47,XXY. Both parents have normal karyotype. In which parent and at which meiotic division did nondisjunction occur?
zygote
normal gamete
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XcXc X+Y
XcX+Y
X+Y
paternal
Xc
maternal
XcX+YX+Y
X+YX+Y
X+Y
Nondisjunction occured during meiosis I in father.
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INCREASING FREQUENCY OFINCREASING FREQUENCY OF THE THE CHROMOSOMCHROMOSOMALAL ABER ABERRRAATIONSTIONS WITH THE AGE OF THE MOTHERWITH THE AGE OF THE MOTHER
0
5
10
15
20
25
30
35
40
45
50
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
maternal age (years)
chro
m. a
bnor
mal
ities
/100
0 liv
ebirt
hs
Down syndrome Total chrom. aberrations
AGE LIMIT -- CHROMOSOMAL
ANALYSIS OF THE FETUS IS RECOMMENDED
(CZECH REP.)
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KARYOTYPE (cca 2 wks)
PRENATPRENATAAL DIAGNOSTIL DIAGNOSTICSCSCHORIONIC VILLI SAMPLE
AMNIOCENTESIS (16.-18.w.)
CORDOCENTESIS
amnioPCR (within 24 hours)
ratio 2 : 1
dialelic form of trisomy 21
trialelic form of trisomy 21
47,XX,+21
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47,XXY
task 10, p.84
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45,X
task 9, p. 82
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47,XY,+21
task 11, p. 86
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47,XX,+13
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47,XY,+18