Direct Vs Indirect Molecular Diagnostic Tests

Genetic testing, through interrogation of DNA, RNA, chromosomes, or proteins, can provide critical information for the detection of heritable disease genotypes for a number of different applications Table 3 15 . Many procedures can be used in either a direct or indirect mutation analysis. Most types Applications of Molecular Genetic Testing Diagnostic testing Testing for a gene mutation in symptomatic individuals as a diagnostic aid. Newborn screening Testing is used to screen populations to...

Constitutional Chromosomal Abnormalities

Microsatellite Instability

Chromosomal abnormalities occur quite commonly. Most are not compatible with life and are aborted spontaneously. Over 50 of early SABs have an abnormal karyotype 21 . The attrition rate of fetuses with chromosomal abnormality decreases as pregnancy progresses, and about 5 of stillbirths 21 and a smaller percentage of term deliveries are chromosomally abnormal. Chromosomal abnormality is a significant cause of major birth defects. Abnormalities of the sex chromosomes are generally better...

Indications For Chromosomal Evaluation

Human Metaphases

AMNIOTIC FLUID The reasons for karyotypic evaluation vary by sample type. Amniotic fluids are the primary sample for prenatal evaluation. Genetic amniocenteses are ideally performed at about 16 wk of gestation and are generally offered to women when their risk of having a chromosomally abnormal fetus is greater than the inherent risk of the amnio-centesis procedure itself. Early amniocentesis can be performed at 10-12 wk. The most common reason for performing a genetic amniocentesis is...

Mendellian Inheritance Patterns

Pedigree For Unaffected Male Symbol

Inheritance patterns of single-gene disorders are based on traditional Mendelian laws of segregation and independent assortment. The following assumptions are made as a result of these laws 1 An offspring inherits one autosomal chromosome from each parent and, thus, one of any given allele from each parent 2 both alleles, regardless of inheritance, are equally expressed and heterozygotes can transmit either allele to their offspring with equal frequency and 3 the phenotypic pattern of...