genetic testing
TRANSCRIPT
GENETIC TESTING
By:-Firoz qureshiDept. psychiatric nursing
DEFINITION In 1999, the Task Force on Genetic Testing defined
a genetic test as:“the analysis of human DNA, RNA, chromosomes, proteins, and certain metabolites in order to detect heritable disease-related genotypes, mutations, phenotypes, or karyotypes for clinical purposes. Such purposes include predicting risk of disease, identifying carriers, establishing prenatal and clinical diagnosis or prognosis. Prenatal, newborn, and carrier screening, as well as testing in high risk families, are included.”
DEFINITION genetic testing is defined as a “ tests to detect
or exclude an alteration likely to be associated
with a genetic disorder”
PURPOSE Finding possible genetic disease in unborn
babies. Finding out if people carry a gene for a
disease and might pass it on to their children. Screening embryos for disease. Testing for genetic diseases in adults before
they cause symptoms. Confirming a diagnosis in a person who has
disease symptoms.
METHODS OF GENETIC TESTING
METHODS OF GENETIC TESTING
1. A karyotype (Greek karyon = kernel, seed or nucleus) is the number and appearance of chromosomes in the nucleus of a cell.
2. Linkage testing: Linkage is the tendency for genes and other genetic markers to be inherited together because of their location near one another on the same chromosome.
A genetic marker is a segment of DNA with an identifiable physical location.
METHODS OF GENETIC TESTING
markers are often used as tools for tracking the inheritance pattern of a gene that has not yet been identified but whose approximate location is known.
Example- polycystic kidney disease3. Methylation studies: examine the attachment of
methyl groups to DNA molecule. DNA methylation is a biochemical process where
a methyl group is added to the cytosine or adenine DNA nucleotides.
METHODS OF GENETIC TESTING
4. Protein truncation test: tests for proteins that have been shortened & whose function has been altered. Example- breast cancer.
5. Uniparental disomy: tests for two chromosomes from same parent rather than one from each.
6. x-inactivation studies: tests for carrier status in women with x-linked disorders.
METHODS OF GENETIC TESTING
7. FISH(fluorescence in situ hybridization) is used to find out the presence or absence of chromosome segment . Mostly use as confirmative test for trisomies.
METHODS OF GENETIC TESTING
Non-DNA based Testing1. Analyte testing: assesses presence of substance in
body indicative of genetic disorder.2. Enzyme assay: measures rate of chemical reaction
of an enzyme in presence of a particular protein associated with genetic disorder.
3. Protein analysis: tests for structure of proteins known to be associated with genetic disorders
TYPES OF GENETIC TESTS
TYPES OF GENETIC TESTS Newborn screening: It is used just after birth to
identify genetic disorders that can be treated early in life.
Diagnostic testing: It is used to identify or rule out a specific genetic or chromosomal condition. In many cases, genetic testing is used to confirm a diagnosis when a particular condition is suspected based on physical signs and symptoms. Diagnostic testing can be performed before birth or at any time during a person’s life. The results of a diagnostic test can influence a person’s choices about health care and the management of the disorder.
TYPES OF GENETIC TESTS Carrier testing: this is used to identify people
who carry one copy of a gene mutation that, when present in two copies, causes a genetic disorder. If both parents are tested, the test can provide information about a couple’s risk of having a child with a genetic condition.
Forensic testing: it uses DNA sequences to identify an individual for legal purposes. This type of testing can identify crime , rule out or implicate a crime suspect, or establish biological relationships between people (for example, paternity).
TYPES OF GENETIC TESTS Preimplantation testing: it is also called
preimplantation genetic diagnosis (PGD), is a specialized technique that can reduce the risk of having a child with a particular genetic or chromosomal disorder. It is used to detect genetic changes in embryos that were created using assisted reproductive techniques such as in-vitro fertilization.
TYPES OF GENETIC TESTS Predisposition and presymptomatic testing: these are
used to detect gene mutations associated with disorders that appear after birth, often later in life. These tests can be helpful to people who have a family member with a genetic disorder, but who have no features of the disorder themselves at the time of testing.
Presymptomatic testing can determine whether a person will develop a genetic disorder. .
Predisposition testing can identify mutations that increase a person’s risk of developing disorders with a genetic basis, such as certain types of cancer.
TYPES OF GENETIC TESTS Prenatal testing: this is used to detect changes in a
fetus’s genes or chromosomes before birth. This type of testing is offered during pregnancy if there is an increased risk that the baby will have a genetic or chromosomal disorder.
INDICATIONS FOR PRENATAL GENETIC
ANALYSIS
PRENATAL DIAGNOSIS & SCREENING
Ultrasonography- in 2nd trimester Amniocentesis-performed in 2nd
trimester(15-20 weeks) Chorionic villus sampling(CVS)- during 9-11
weeks Umbilical vein blood
sampling(cordocentesis) Triple screen test-this is maternal serum
screening.
LEGAL & ETHICAL ISSUES IN GENETIC
TESTING
ROLE OF NURSE IN GENETIC TESTING
The nurses are responsible for alerting clients of their rights to make an informed decision prior to any genetic testing with considering of special circumstances arising from the Family, culture and community life.
All genetic testing should be voluntary and it is the nurse’s responsibility to ensure that the consent process include discussion of the risk and benefit of the test.
ROLE OF NURSE IN GENETIC TESTING
Nurses need to ensure client’s confidentiality and privacy of genetic testing.
Nurses should address psychological, social and economic issues of person and family undergoing for genetic testing.
ROLE OF NURSE IN GENETIC TESTING
Take informed written consent from patient. Administer prophylactic antibiotic in invasive
tests as per institution’s policy. Offer counseling services as per need of the
patient and family. Inform about follow-up and test result
availability
RESEARCH ABSTRACTDNA sequencing of maternal plasma reliably identifies
trisomy 18 and trisomy 13 as well as Down syndrome: an international collaborative study:
Glenn E. Palomaki PhD, et.al.Purpose: To determine whether maternal plasma cell–free
DNA sequencing can effectively identify trisomy 18 and 13.Result: Among high-risk pregnancies, sequencing circulating
cell–free DNA detects nearly all cases of Down syndrome, trisomy 18, and trisomy 13, at a low false-positive rate. This can potentially reduce invasive diagnostic procedures and related fetal losses by 95%. Evidence supports clinical testing for these aneuploidies.