4. NUMERICAL ABNORMALITIES
Euploid-any exact multiple of haploid
Aneuploidy-chromosome compliment that is not an exact mutiple of 23
Nondisjunction
Anaphase lag
Mosaicism-mitotic error in early development give rise to 2 /more population
of cells with different chromosomal complement in some individual
EG-45X/47XXX mosaic
14. SPONTANEOUS ABORTIONS
1 in 200 live born children is chromosomally abnormal
95% of chromosomally abnormal conceptus are aborted spontaneously
Abortion mostly occurs in 1st trimester
15. DOWN SYNDROME
Incidence-1 in 700
95% have trisomy 21,chromosome no 47
1% cases are mosaics.-mitotic nondisjunction
4% cases-extra chromosomal material derives from presence of robertsonian
translocationof long arm of chromosome 21 to acrocentric chromosome.
10 to 20 fold increased risk of deveoping leukemia
16.
17.
18. CHROMOSOME 22q11.2 DELETION SYNDROME
Small deletion of band q11.2 on long arm of chromosome 22.
1 in 4000 births
Congenital heart defects ,palatal abnormalities, facial dysmorphism,
developmental delay,T-cell immunodeficiency and hypocalcemia
High risk for schizophrenia and bipolar disorder
19. TRISOMY 18
Incidence 1/8000
Overlaps with trisomy 13
Sever Mental retardation
>90% dead in 1st year
Small face with prominant occiput
Small sternum and pelvis
Flexion deformity of the finger
VSD and horseshoe kidney
20.
21. TRISOMY 13(PATAU SYNDROME)
Severe developmetal retardation
Incidence 1/20000
90% dead in the 1st year
Midline brain defect
Malformed ear
Micropthalmos and coloboma
Scalp defect
25. TURNER SYNDROME
Complete or partial monosomy of X chromosome
Hypogonadism in phenotypic females
1 in 2000 live born females
57% missing an entire X chromosome-45,X karyotype
14% have structural abnormalities of X chromosome
29% are mosaics
Structural abnormalities are-
Deletion of small arm-isochromosome of long arm-46,X,i(X)(q10)
Deletion of portion of both long and short arms-ring chromosome-46,X,r,(X)
Deletion of portion of short or long arm-46X,del(Xq)
Mosaic patterns-
45,X/46,XX
45,X/46,XY
45,X/47XXX
45,X/46,X,i(X),(q10)
26. Female, short stature, primary amenorrhea, sterility, spares hair and
underdeveloped breast
Neonatal: wide spaced nipple, lymphedema , shield chest,
27. KLINEFELTER SYNDROME
Male hypogonadism occur when there are 2 /more X chromosome and one
/more Y chromosome.
1 in 660 live male births
Eunuchoid body habitus,abnormally long legs,small atrpohic testis,lack of
secondary male characteristics
Increased incidence of type 2 diabetes,metabolic syndrome
Higher risk of breast cancer,extragonadal germ cell tumor and autoimmune
diseases
47,XXY-90% cases
15% cases are mosaics
28.
29. HERMAPHRODITISM
GENETIC SEX
PHENOTYPIC SEX
PSEUDOHERMAPHRODITISM
TRUE HERMAPHRODITISM
FEMALE PSEUDOHERMAPHRODITISM-excessive and innapropriate
exposure to androgenic steroids during early gestation
MALE PSEUDOHERMAPHRODITISM-extremely heterogenous.most
common –defective virilization of male embryo(complete androgen
insensitivity syndrome)
30. KARYOTYPING
3 main methods to identify chromosomes
G BANDING-------giemsa
Q BANDING-------quinacrine
R BANDING-------reverse
31. SUBCLASSIFICATIONS OF BANDING METHODS
ISCN 1985
3 letter code to describe banding techniques.
Ist letter---type of banding
2nd letter—general technique
3rd letter—the stain
Eg-QFQ------Q band by flourescence using quinacrine
32. G BANDING
System of dark and light bands throughout the euchromatin part of
chromosome
Staining technique where chromosomes are treated with trypsin then with
giemsa stain
Needs metaphase
Culture cells until sufficient mitotic activity
Add colchicine to arrest in metaphase
33.
34. TERMS AND DEFINITIONS OF VARIOUS ABERRATIONS OF
CHROMOSOMES
Ring( r)
Dicentric(d) Hyperdiploid (h)
Chromosome gap (sg) Chromatid deletion (td)
Fragment (f) Acentric fragment (af)
Translocation (t) Triradial (tr)
Quadriradial (qr)
Complex rearrangement (cr)
Polyploid (pp) or endoreduplication
35. FLOURESCENT IN SITU HYBRIDISATION(FISH)
Fluorescence in situ hybridization (FISH) uses fluorescent molecules to ―paint‖
genes or chromosomes.
This technique is for gene mapping, identification of chromosomal
abnormalities
FISH involves the use of short sequences of single-stranded DNA (probes)
which are labeled with fluorescent tags, to hybridize, or bind, to the
complementary DNA to see the location of those sequences of DNA under the
fluorescent microscope.
38. ADVANTAGES OF FISH
Rapid
High efficiency of hybridization and detection
Lots of cells can be analyzed
Cells do not have to be replicating
39. SPECTRAL KARYOTYPING
Chromosomal and subchromosomal painting probes that make use
of sorted or microdissected chromosomes
40.
41. Mixtures of fluorophores used to separately label chromosome-specific probes
These are mixed and hybridized en masse
Interpreted via spectral interferometer
Tremendously useful in detecting insertions and translocations,
especially in cancers.