CLS 251 UNIT 3 CONCEPT MAP

bolded only

what are blood group systems?

group of antigens on the RBC membrane that share related serologic properties and genetic patterns of inheritance

what is a phenotype?

physical (observed) expression of traits

what is a punnett square used for?

used to predict the probability of an offspring’s genotype

summarizes every possible combination of maternal and paternal alleles of a particular gene

what is codominant?

equal expression of two different alleles → most blood group antigens are codominant

what is amorphic?

genes that do not express a detectable product due to loss of function

when does linkage occur?

when 2 genes that are close to each other are inherited together

what is a haplotype?

each set of linked genes

where are most blood group system genes located?

on autosomes

where are Xg genes (sex linked) found?

on the X chromosome

what happens if the father carries the Xg allele?

he will pass it to all of his daughters

what happens if the mother carries the Xg allele?

all of their children will express Xg

what is a person called if a person inherits identical alleles?

homozygous

AA, BB, MM (M+ N-)

what is a person called if a person inherits different alleles?

heterozygous

what is dosage?

a variation in antigen expression due to number of alleles present

what is “double dose”?

in some blood group systems, a person homozygous for an allele will have a double dose of an antigen on their RBCs compared with a person who is heterozygous for an allele

what can affect the expression of the antigen?

location of inherited genes in cis or trans positions

what is a cis position?

alleles on the same chromosome

what is a trans position?

alleles on opposite chromosomes

what is the definition of population genetics?

studies of the frequency of genetic variation in different human populations and the use of genetic variants for characterizing genetic differences among humans

what does a phenotype calculation enable?

enables finding a unit of RBCs with certain antigen characteristics

what is the hardy-weinberg formula calculate?

calculates a determination of the gene frequencies that produced a trait

how would you calculate a phenotype if a patient with multiple antibodies needs blood?

convert all percentages into decimals then multiply

how would you calculate a phenotype if a patient with multiple antibodies needs X amounts of units?

convert all percentages into decimals then multiply then divide # of units needed by antigen negative frequency

what does p and q represent in the hardy-weinberg formula?

• p represents allele 1

• q represents allele 2

how is gene frequency represented in the hardy-weinberg formula?

p + q = 1

what are the genotype proportions in the hardy-weinberg formula?

(p + q)² = 1.0 or p² + 2pq + q² = 1.0

what does the landsteiner’s rule state?

that healthy individuals possess ABO antibodies to the ABO blood group antigens absent from their RBCs

who coined the term horror autotoxicus?

german immunologist and nobel laureate, paul ehrlich in 1845 - 1915

when are ABO antigens detected?

in the embryo as early as 5 to 6 weeks gestation

what is a null cell?

O cells lacking both A and B antigens → will have many H antigen sites

what blood group is the universal recipient?

AB patients

what blood group is the universal donor?

O patients

what does the H gene control?

the presence or absence of the ABH antigens on the RBC membrane

what does the Se gene influence?

the presence of absence of the ABH antigens in secretions

what is the oligosaccharide chain?

basic precursor structure for several RBC antigens, including A, B, and H

what antigen is the foundation for the A and/or B antigens?

H antigen

what does the H gene code for?

codes for a glucosyltransferase enzyme that transfers the immunodominant sugar, L-fucose

what does the A gene code for?

codes for a transferase that adds the immunodominant sugar, N-acetylgalactosamine

what does the B gene code for?

codes for a transferase that adds the immunodominant sugar, D-galactose

what percentage of A or AB individuals are A₁?

80%

what percentage are A₂ and A₂B?

20%

why is it important to identify subgroups?

to avoid transfusing ABO incompatible blood, avoiding a transfusion reaction, and a BAD patient outcome

what are ABO antibodies?

non-RBC stimulated and may not be detected until 3 to 6 months of age

what are the antibodies in blood group O?

• anti-A

• anti-B

• anti-A,B

antibody class is mostly IgG

what is the Anti-A1 antibody?

produced by subgroups of the ABO group A type rather than A1 when exposed to A1 cells… has specificity to the A₁ antigen but will not agglutinate A₂ cells & may cause incompatible crossmatches on IS testing

what is forward grouping?

RBCs are tested for ABO antigens

what is reverse grouping?

serum or plasma is tested for ABO antibodies

if a patient is group A, what types can be given to them in whole blood, RBCs, and plasma?

whole blood

• A

RBCs

• A, O

plasma

• A, AB

if a patient is group B, what types can be given to them in whole blood, RBCs, and plasma?

whole blood

• B

RBCs

• B, O

plasma

• B, AB

if a patient is group AB, what types can be given to them in whole blood, RBCs, and plasma?

whole blood

• AB

RBCs

• AB, A, B, O

plasma

• AB

if a patient is group O, what types can be given to them in whole blood, RBCs, and plasma?

whole blood

• O

RBCs

• O

plasma

• O, A, B, AB

when do ABO discrepancies occur?

when the forward grouping does not agree with the reverse grouping

what are the causes for extra agglutination?

• anti-A₁

• cold alloantibodies

  • antibodies specific for human RBC antigens that react at room temp or below

• cold autoantibodies

  • antibodies specific for autologous antigens that react at room temperature or below

• rouleaux

  • false-positive agglutination, saline replacement of serum best resolution for rouleaux

what is the bombay phenotype?

RBCs lack the H antigen (hh) & first reported in 1952 in bombay, india

what can only be used for those who have the bombay phenotype?

only autologous units or rare donor units can be used

who linked the Rh system to HDFN?

levine and stetson in 1940

what did landsteiner and wiener find regarding anti-Rh?

15% of RBCs did not agglutinate and are thus Rh negative

when stimulated by Rhesus monkey RBCs, what was found regarding human anti-Rh?

found that human anti-Rh was similar to guinea pig and rabbit antibodies produced when stimulated with Rhesus monkey RBCs

what is the order of the genes? how are they sometimes ordered?

order of genes is usually DCE but they are sometimes ordered alphabetically as CDE

what antigen is the most immunogenic in the Rh system?

D antigen

what is a genotype?

the genetic makeup and can be predicted by using the phenotype and by considering the race of an individual

what is phenotype the result of?

the result of the reaction between the RBCs and the antisera

what blood should D-negative individuals receive?

should receive D-negative blood

if they receive D-positive blood, it may produce an anti-D in response

what happens if a person is exposed to the D antigen a single time?

may result in the formation of anti-D

what is D antigen composed of?

composed of several component antigens (mosaic)

what is weak D antigen?

RBCs that test positive only by the indirect antiglobulin test (IAT) at AHG → IAT is usually required to detect the weak antigen

when may the D antigen appear weak?

when the C antigen is inherited trans to D

what blood should patients who are weak D positive not receive?

cannot receive D positive blood

what are Rh antibodies?

usually RBC stimulated from transfusion or pregnancy and most are immunoglobulin G (IgG₁)… does not activate complement

what are useful for identifying Rh antibody?

potentiators

what antibodies react stronger to homozygous antigens (dosage)?

antibodies to C, c, E, and e