Karyotyping: Spying The Faulty Genes

 

Ms. Rashmi Sharma

Clinical Instructor, Army College of Nursing, Jalandhar Cantt.

 

ABSTRACT:

Karyotype is number of chromosomes and its appearance in the nucleus of a eukaryotic cell³. And the study of karyotype is called Karyotyping or chromosomal analysis. It provides insight to the genes in order to detect any genetic and chromosomal problems. A small sample of individual’s cells is sufficient to rule out root cause of genetic disorder. In this, chromosomes of an organism are paired and ordered by using standardised staining procedure, enables to analyze its characteristics and structural features². It reveals chromosomal deletions, translocations, duplication and inversions². Karyotyping in the present scenario indeed act as a boon and ensure wellbeing of foetus.

 

 

 

INTRODUCTION:

Arrival of physically and mentally handicap baby surely influences the family deeply and inculcate the guilt feeling among them. Several factors like adopting sedentary lifestyle, unhealthy food consumption, environmental changes, conceiving after the age of 30, hectic schedules, stress and many more led human being of this modern world to undergo several changes. These transitions in day to day life are enough potent to cause the genetic material alterations. Due to these mutations the percentage of babies with genetic disorders is rising. To halt this spike, ultrasound scan is the most commonly used tool to monitor the foetal well being. Through this, plethora of disorders and complications can be ruled out. However, USG findings that are sometimes are suggestive of abnormal fetal growth requires further confirmation to track the faulty genes causing this, by analysing chromosomal material called karyotyping.

 

DEFINITION:

Karyotyping is also known as chromosomal analysis, is being used in wide variety of tertiary hospitals to detect all of the visible traits of chromosomes in the specific cell. A karyotype can be defined as number and appearance of chromosomes in the nucleus of a eukaryotic cell³. Chromosomes contain thousand of genes in specific location; it contains body’s genetic blueprint.

 

INDICATIONS:

For prenatal karyotyping:

·      Known or suspected family history of chromosomal abnormalities⁵

·      Cancer diagnosis (tumour biopsy)

·      Early spontaneous abortions⁴

·      Predominantly trisomies¹

·      Polyploidy

·      Monosomy X

·      Fetal death with multiple congenital abnormalities or dysmorphic features⁵

 

For postnatal karyotyping:

·      Ambiguous genitalia/indeterminate gender

·      Delayed puberty or inappropriate secondary sexual development

·      Short stature, amenorrhoea in females.

·      Oligospermia or azoospermia

·      Unexplained learning difficulties/developmental delay/behavioural problems.

 

Parentral Karyotyping:

·      Known or suspected family history of chromosomal abnormalities

·      Pregnancy loss of unkaryotyped fetus with multiple congenital abnormalities or severe IUGR

·      Multiple congenital abnormalities⁶

 

ADVANTAGES:

·      The chromosomal analysis has allowed the physician to diagnose any chromosomal abnormalities like Down syndrome, Turner Syndrome, Edwards syndrome⁴; certain hematologic, lymphoid disorder in an individual and birth defects in foetus during the pregnancy.

·      Helps in ruling out cause of recurrent miscarriages, infertility among couples⁴.

·      Identifies cancer specific genes

·      Provides direction for molecular studies of pathogenetically important genes

·      Highly reliable diagnostic test, sensitive and specific in nature

·      Provides wide range of information in a single assay

 

SAMPLING SOURCES:

·      Chorionic villi (chorionic villi sampling)

·      Amniotic fluid (amniocentesis)

·      Bone marrow biopsy

·      Vein (for blood cell study). The cells collected in the sample are sent to specialised laboratories for examinations⁶

·      Skin biopsies, tumour biopsies

·      Tissue from miscarriage or still birth

·      Tissue from child with congenital abnormality

 

PROCEDURE:

Sample is obtained → cultured in nutrient enrich medium → undergoes cell division, observed in growth phase (as are easy to distinguish) → cell divisions arrested using colchicines → isolating the chromosomes → rearranged vertically according to size, placement of centromeres and structure in pairs 1 to 22 followed by pair of sex chromosome(banding pattern)² → slide preparation using different types of stains (G- stains) and karyograms¹ → fixation done on slides → microphotographs are taken → observation for alteration in structure, number of genes².

 

LIMITATIONS:

·      Expensive

·      Complex karyotypes take longer time for evaluation

·      Requires specialised equipments and expert for interpretation

·      Requires fresh tissues

ROLE OF NURSE:

·      Create awareness among people regarding this test.

·      Nurse can help in early detection and management of congenital anomalies.

·      Educating parents for genetic testing to fix recurrent miscarriages.

·      Reducing population of genetic handicaps by guidance to parents.

·      Health education regarding healthy diet, avoidance of junk food, protection from harmful rays, stress buster activities, counselling, at least four antenatal visits and precautions to be taken in high risk pregnancies.

 

CONCLUSION:

With the advent of genetic testing, early detection and intervention of some of the disorders is possible. However, in developing countries like India, many people being unaware of it are incapable of getting its benefit. They accept genetic disorders as a part of their destiny. Awareness can act as a wizard for those with inherited ailments. Each medical personnel has important role to play in imparting education regarding karyotyping³ in order to raise the healthy society.

 

 

Figure no. 1 Showing normal male karyotype

 

 

Figure no. 2 showing karyotype showing trisomy 21, down syndrome

 

REFERENCES:

1.     https://www.nature.com/scitable/topicpage/karyotyping-for-chromosomal-anormalities-298

2.     https://www.labtestsonline.org.au/learning/test-index/chromosome-analysis-karyotyping

3.     https://en.wikipedia.org/wiki/Karyotype

4.     https://www.webmd.com/baby/what-is-a-karyotype-test#1

5.     https://www.verywellhealth.com/how-to-how-is-a-karyotype-test-done-1120402

6.     https://www.lalpathlabs.com/blog/karyotype-test/

 

 

 

Received on 16.05.2019        Modified on 31.05.2019

Accepted on 21.06.2019      ©A&V Publications All right reserved