Haemophilia

It is a group of hereditary genetic disorders that impair the body's ability to control blood clotting or coagulation, which is used to stop bleeding when a blood vessel is broken. Characteristic symptoms vary with severity. In general symptoms are internal or external bleeding episodes, which are called "bleeds”. Patients with more severe haemophilia suffer more severe and more frequent bleeds, while patients with mild haemophilia usually suffer more minor symptoms except after surgery or serious trauma. Moderate haemophiliacs have variable symptoms which manifest along a spectrum between severe and mild forms. The karyotype for hemophilia looks just like that of non-hemophilia. This is because hemophilia only affects a small part of the X chromosome.

Color Blindness

the inability or decreased ability to see color, or perceive color differences, under normal lighting conditions. The most usual cause is a fault in the development of one or more sets of retinal cones that perceive color in light and transmit that information to the optic nerve. This type of color blindness is usually a sex-linked condition. The genes that produce photopigments are carried on the X chromosome; if some of these genes are missing or damaged, color blindness will be expressed in males with a higher probability than in females because males only have one X chromosome (in females, a functional gene on only one of the two X chromosomes is sufficient to yield the needed photopigments).

Diagnosis : The Ishihara color test, which consists of a series of pictures of colored spots, is the test most often used to diagnose red–green color deficiencies. A figure (usually one or more Arabic digits) is embedded in the picture as a number of spots in a slightly different color, and can be seen with normal color vision, but not with a particular color defect. Doesn’t show up in karyotype.

Date: 2014-12-21; view: 1215