The spectacular advances in molecular biology have led to the localization and identification of numerous genes involved in genetic pathologies.
The Department of Genetics provides comprehensive prenatal genetic testing to determine whether a pregnancy may be affected with a birth defect or genetic condition.
Prenatal Genetics identifies individuals at increased risk for carrying a fetus with a specific birth defect, provides up-to-date information about the inheritance of genetic conditions, the cause of various birth defects, and the tests that are available to determine whether an individual/couple has a chance to have a child with that condition or birth defect.
Our Prenatal Genetics Departments Center provides an early, accurate, convenient and safe option for chromosomal aneuploidies and gender determination.
Y chromosome microdeletion is the most frequently encountered genetic abnormality in male infertility. The estimated frequency of Yq11.21-23 microdeletions is 10 – 15% in cases of azoospermia (absence of sperm) and 5 – 10% in cases of oligospermia, Y chromosome microdeletions typically occur de novo.
Azoospermia is known to be associated with deletions in azoospermia factor (AZF) regions of the Y chromosome. There are 13 common deletion sites (SY81, SY84, SY86, SY121, SY124, SY127, SY128, SY130, SY133, SY134, SY182, SY254 and SY255) in 3 AZF regions (a, b and c) that have been screened. Microdeletions of the AZFa region are mainly associated with Sertoli Cell-Only Syndrome (SCOS; Spermatogenic failure); 5% of cases. Microdeletions of the AZFb region are mainly associated with azoospermia/spermatogenic arrest; 10% of cases. Microdeletions in both the AZFb and AZFc are associated with SCOS/spermatogenic arrest; 13% of cases. A range of phenotypes from azoospermia to oligospermia are associated with the absence of the AZFc region; 70% of cases.
Y-chromosome microdeletions are detected using genetic markers called sequence tagged sites (STS) which map along the length of the long arm of the Y chromosome. These STS are PCR-amplified, and the products are subjected to gel electrophoresis. The absence or presence of DNA indicates whether or not deletions are present on the Y chromosome.
Small amounts of a baby’s DNA pass into the blood stream of the mother during pregnancy. New technology allows us to analyze this DNA directly from the mother’s blood and screen for chromosomal abnormalities. Until recently it has only been possible to screen for abnormalities with highly invasive procedures such as chorionic villus sampling (CVS) or amniocentesis. These tests carry an elevated risk of miscarriage and are only performed later in pregnancy. Initial screening with Janini can help to avoid this potentially unnecessary and invasive testing. There is no risk to mother or baby and Janini provides the earliest testing available.
Janini delivers a clear positive or negative result for chromosomal abnormalities where an extra copy of one chromosome is present (Trisomy). Down syndrome, the most common chromosomal abnormality, can be detected with an accuracy rate of >99.9%.
Janini also screens for changes in the number of X or Y chromosomes. The test is also suitable if you are pregnant with twins.
What does Janini screen for?
The test can also detect abnormalities of the sex chromosomes:
Why should you choose Janini test?
How is the test is performed?
A single blood sample, collected from mother. Test results are typically provided to your physician within 10 days of sample date received.
|Gently invert the tube ten times immediately after blood sampling.
Whole-genome sequencing with next-generation sequencing (NGS) technology to analyze cfDNA fragments across the whole genome, which has proven advantages over other NIPT methodologies such as targeted sequencing and array-based methods. Test failure rates are substantially lower with whole-genome sequencing versus other methodologies.
janini (XY) test
Early sex determination has evolved from invasive techniques such chorionic villus sampling and amniocentesis to noninvasive prenatal testing through the analysis of cell-free fetal DNA (cffDNA). The identification of fetal DNA in maternal blood paved the way for subsequent analysis of fetal DNA for non-invasive prenatal diagnosis.Since its discovery, several studies have shown detectable amounts of cffDNA in maternal circulation as early as 10 weeks gestation.
cffDNA represents about 10% of the total cell-free DNA in maternal plasma at 10 weeks gestation. Multiple studies have demonstrated the use of maternal plasma DNA for fetal sex determination.These studies utilized Y-chromosome target sequences.
Test is based on a novel real-time PCR system for quantification of total human (autosomal) and human male (Y) DNA using cell-free DNA (cfDNA) prepared from a blood sample of a pregnant women; this test has been validated in single pregnancy of at least 10 weeks gestational age. The technology takes advantage of the specific interaction between two modified nucleotides to achieve quantitative PCR analysis. Generated data are exported to the analysis software to determine the presence or absence of the (Y) DNA.
Fetal gender results should be considered in combination with other standard of care information, such as the results from sonographic screening.
For further information, please contact: