GENETICS

Genetics is still fun at this stage. Just when you thought you have learned it all about blood groups, something new never fail to amuse you. From AB, A, B, O to M, N, RhD to Bombay blood type this morning, and I discovered para-Bombay blood type just now, no joke.


The Bombay phenotype is characterized by a complete absence of ABH activity both on red blood cells and in secretions, and by the presence of anti-H, anti-A and anti-B antibodies in the serum because of the absence of both the H and Se enzyme activities. The para-Bombay phenotype (H deficient secretor) is characterized by a lack or a very weak expression of the ABH activity on red cells, and by a presence of ABH substances in secretions because of an absence of the H enzyme activity and a presence of Se enzyme activity.

Taken from: Baojie Wang, Yoshiro Koda, Mikiko Soejima, Hiroshi Kimura. Vox Sanguinis. Basel: Jan 1997. Vol. 72, Iss. 1; p. 31 (5 pages)


Another thing noted by my lecturer was X-inactivation, a genetic regulatory mechanism which operates to equalize the phenotypic expression of characteristics determined by genes on the X chromosome so that they are equally expressed in the human XY male and the XX female.

Of course this makes lots of sense but I too ponder upon the Q put forwarded by my lecturer.

How come those with Turner Syndrome with X0 chromosomes are sterile then?


The existence of genes along the inactive X which are not silenced explains the defects in humans with abnormal numbers of the X chromosome, such as Turner syndrome (X0) or Klinefelter syndrome (XXY). Theoretically, X-inactivation should eliminate the differences in gene dosage between affected individuals and individuals with a normal chromosome complement, but in affected individuals the dosage of these non-silenced genes will differ as they escape X-inactivation.

Too bad those sentences are not cited.

http://en.wikipedia.org/wiki/X-inactivation


Forensic Heroes 2: Episode 21 around the first 11 minutes Dr. Koo tells Madam Ma that her father is fine and Dr Li is going to take care of him. But Mr Ma has a rare blood type called Para Bombay Type A and Dr Koo says he will check blood banks for it which he will probably not find. Since most blood banks rarely stock this rare blood type as rare as it is to find someone that has it.

http://en.wikipedia.org/wiki/Bombay_phenotype

So either the entry is wrong or forensic heroes 2 script is faulty. Bombay blood type can't exist as type A.