CYTOGENETICS DEFINITION

                     

                  CYTOGENETICS

Cytogenetics definition 

Cytogenetics is defined as the the science that combines the method and findings of cytology and genetics to investigate heredity at the cellular level this involves Evolutions of chromosomes. genetic is scientific study of heredity in clinical laboratory medicine to fields of interest are Human Genetics and medical genetics

CYTOGENETICS 

IMPORTANCE OF CYTOGENETICS STUDIES

  The cells from a patient  must be cultured in vitro, to obtained  metaphase cells. but any nucleated cell specimen can be used for routine cytogenetic studies heparinised  peripheral blood is the preferred specimen.
In hematologic disorder the best results are obtained from bone marrow sample which is a source of disease process.
An adequate source of metaphase cells can be obtained from skin biopsy or skin punches.
All specimens for cytogenetic analysis must be collected in sterile manner and should be transported to the laboratory as soon as possible.blood, amniotic fluid, bone marrow etc, should be maintained at room temperature (25°+-5°). solid tissue should be transported on wet ice.
But chromosomes are best studied in metaphase techniques such as FISH may require cells in interphase. metaphase chromosomes are observed in spontaneously dividing cell such as bone marrow progenitor stem cells, cells of testis, lymph node, solid tumor etc, the cells such as leukocytes, fibroblast and amniotic fluid cells are cultured before the cytogenetic studies.

Cytogenetic studies for use of cell culture

The average human cell divides once every 24 hour. lymphocyte are preferred for cell culture. however Lymphocytes in a normal healthy individual do not divide at all hence, special culture techniques have been developed to stimulate the cells to divide and increase the yield of metaphase cells. for routine cytogenetic studies of adult and children heparinized blood is used from which Lymphocytes are obtained for cell culture.

Cytogenetic studies for tissue

To collect samples required for prenatal diagnosis a minor operation theatre with ultrasound facility is required.

Clinical cytogenetic tests (CTT)

CTT is used to find out chromosome anomaly caused either by a physical problem or due to phenotypic abnormality in the patient. there are two basic categories of cytogenetically detectable  variation:- 1 numerical and 2:- structural changes.

Prenatal cytogenetics

On average 15% of all recognized pregnancies and in a spontaneous fetal loss, 80% of these pregnancy terminations occurs in the first trimester of all spontaneous abortions, 60% are chromosomally abnormal and of these 52% autosomal trisomies.  is the most frequent class of chromosome error in spontaneous Losses in 45, X and the most common trisomy seen in abortus material is trisomy 16.
Chromosome abnormalities in spontaneously fetal losses and in liveborn infants

CYTOGENETICS DEFINITION 

Other cytogenetic disorders

1:-Fragile X syndrome :- a break or gap in the structure of the X chromosomes may lead to Fragile X syndrome, which is the second leading cause of mental retardation and is the primary cause of inherited mental retardation. this disorder can be detected cytogenetically by culturing cells in the appreciate induction medium.
2:- Breakage syndromes:- In the following table some of the chromosome syndromes are listed.