Water-siphon test. Dr Henry Knipe â and Dr Marcin Czarniecki â et al. The water siphon test may be performed as part of a barium swallow to assess for gastro-oesophageal reflux in a hiatal hernia. It is performed in the supine RPO position with the patient drinking water continuously. The test is said to be positive if there is visible barium reflux in the oesophagus.
In some instances, offspring can demonstrate a phenotype that is outside the range defined by both parents. In particular, the phenomenon known as overdominance occurs when a heterozygote has a more extreme phenotype than that of either of its parents. Indeed, in a few examples, a trait that shows overdominance sometimes confers a survival advantage in the heterozygote (Parsons & Bodmer, 1961).
Gene Amplification, also known as gene duplication or chromosomal duplication, is a cellular process in which multiple copies of a gene are produced.The result is an amplification of the phenotype, or expressed trait, associated with the gene.ot all gene amplification has great importance to evolution. Sometimes, the amplified trait dies with the single organism that experiences the gene duplication. This happens when a gene is over expressed and the trait it codes for is expressed to a level that is unhealthy to the organism.