RzRz

RR is a very rare Rh genotype in the Rh blood group system, mostly occurring in Native Americans. It is one of the notable abnormalities in John Amsterdam's medical records. It implies that John's blood changed when the Lenape gave him immortality.
John's other blood abnormalities include:
* high hemoglobin level
* toxic level of lead
* fast blood clotting
* ten times the normal platelet level
* very low levels of factor VIII
==Real world facts==
To understand what RR means, some background on the Rh blood group system is helpful:
*The Rh blood group system has five main antigens. They are D, C, E, c, and e. (There is no lower-case 'd' antigen.)
**The commonly used terms Rh factor, Rh positive and Rh negative refer to the D antigen only. When a person can inherits the D antigen from both parents or from a single parent, the person is Rh positive. If a person does not inherit the D antigen from either parent than s/he is Rh negative. Rh negative is a recessive trait. A person who is Rh negative can have parents who were both Rh positive (though both must have been heterozygous). A person who is Rh positive must have at least one parent who was Rh positive. 
**From each parent, a person inherits either the C or c antigen. A person who inherits the C antigen from both parents lacks the c antigen. On the other hand, a person who inherits the c antigen from both parents lacks the C antigen. A person can have both the C and c antigens if s/he inherits the C antigen from one parent and c antigen from the other parent.
**The E and e antigens work alike to the C and c antigens.
*There is two nomenclatures used for genotypes of the Rh blood group. They are called the Fisher-Race notation and Wiener notation.
**The Fisher-Race notation is more widely used today because it is simpler to explain. It uses "D", "C", "E", "c", and "e" to indicate the presence of each of the main five antigens. It also uses "d" to indicate the absence of the D antigen. (There is no d antigen.)
***For example, the Fisher-Race notation DCe/dcE means a person inherited the D, C, and e antigens from one parent and the c and E antigens from the other parent. 
**Wiener notation uses "R" to represent presence of D antigen and "r" for lack of D antigen. It then adds marks to indicate presence of C, E, c, and e antigens.
***To compare Wiener and Fisher-Race haplotypes: R = Dce, R = DCe, R = DcE, R = DCE, r = dce, r′ = dCe, r″ = dcE, r = dCE.Rh Terminology and Genetics, the missing illustration
***For example, a genotype written as DCe/dcE in Fisher-Race notation is written as Rr″ using Wiener notation.
Facts about RR:
*RR is Wiener notation for John's Rh genotype. The Fisher-Race notation for this genotype is DCE/DCE. That means the phenotype is D+ C+ E+ c- e-, meaning he has the D, C, and E antigens but lacks the c and e antigens.
**A person with D+ C+ E+ c- e- phenotype can have either RR (DCE/DCE) or Rr (DCE/dCE) genotype. The difference is that a person with RR genotype inherited the D antigen from both parents while a person with Rr genotype inherited the D antigen from only one parent. For both genotypes, a person would have inherited the C and E antigens from both parents but lack the c and e antigens.
*While in the show, Sara Dillane says the RR blood type went extinct, in reality it still occurs today. RR occurs in less than 0.05% of the population (<5 in 10,000), it was more common in Native Americans and Native Alaskans.
Facts about John's other blood abnormalities:
*John has 120 micros of lead in his blood, which is triple the adult toxic level, and 12 times the safe level for children.
*John's fast clotting and high platelet level, is despite the low levels of factor VIII which would normally cause hemophilia.
==Relevant dialog==
; 101 "Pilot"
Nurse: 	"Got the blood work back on your disappearing corpse, and it’s a mess."
Dillane:	"Hmm. No, this must be a lab error. These numbers don’t make sense. I mean, the hemoglobin level’s over the moon. 120 micros of lead? That’s enough to kill someone."
Nurse: 	"Yeah, and check out the blood type. It’s this rare form of RR."
Dillane:	"It became extinct when certain Native American tribes disappeared."
Nurse: 	"So, somebody’s pulling our chain?"
Dillane:	"Hope so."
; 103 "Soldier’s Heart"
Dillane:	"Your blood work was curious. It had anomalies."
John: 	"Anomalies?"
Dillane:	"A toxic level of lead. Native American genetic markers."
John: 	"A great-great-great-great-grandmother was part Lenape."
Dillane:	"Lenape?"
John: 	"The original inhabitants of Manhattan."
Dillane:	"The ones who sold it to the Dutch?"
John: 	"Old wives’ tale. Trust me, it never happened."
; 104 "Honor"
Dillane:	"See how fast your blood clots? I got back some more of your tests. Your platelet level is 10 times normal, and you have very low levels of factor VIII."
John: 	"I love it when you talk medical."
==References==