3.07 Blood Type Origins

Question 1

Concept wherein a certain gene has many alleles across the population

Answer 1

polymorphism

Question 2

Where many genes encode for the same phenotype

Answer 2

polygeny

Question 3

Inheritance pattern wherein the offspring expresses both sets of genes from parents

Answer 3

co-dominance

Question 4

The basic mechanism on how the blood system works (key terms: antibodies, antigens)

Answer 4

Antibodies bind to antigens on foreign RBCs marking them for the extermination of the immune system (activates the complement cascade)

Question 5

Serves as the precursor for other ABO blood types

Answer 5

H antigen

Question 6

The four monosaccharide rings that compose the precursor for the ABO blood types

Answer 6

galactose, N-acetylglucosamine, another galactose and fucose

Question 7

The H antigen is completed by the enzyme __

Answer 7

fucosyltransferase

Question 8

Fucosyltransferase is encoded by the __ gene on chromosome 19, and it evidently adds the monosaccharide __.

Answer 8

FUT1; 19; fucose (4th)

Question 9

The ABO locus is located in which chromosome?

Answer 9

chromosome 9

Question 10

The blood type of a person is dictated by this general mechanism of antigen synthesis (three-step mechanism)

Answer 10

allele –> enzyme –> monosaccharide

Question 11

What are the corresponding enzymes and monosaccharides responsible for the four blood types?

Answer 11

A - alpha-1,3-N-acetylegalactosamine transferase - H antigen + GlcNac
B - alpha-1,3-galactosyl transferase - H antigen + Gal
O - NO enzyme - nothing added to H antigen

Question 12

What causes the lack of an enzyme for the O antigen?

Answer 12

Deletion of guanine at position 261 of exon 6

Question 13

Inactive counterpart of the H allele

Answer 13

h

Question 14

What does having a homozygous h/h do to a person?

Answer 14

It removes the ability to produce the enzyme fucosyltranferase, thereby rendering the H antigen incomplete. It makes it difficult for them to receive blood through transfusion because their bodies will recognize non-homozygous h blood types as foreign.

Question 15

What do you call the phenotype for homozygous h individuals?

Answer 15

Bombay phenotype

Question 16

T/F. ABO antigens are either membrane-bound or free form.

Answer 16

True

Question 17

If the antigens are membrane-bound, they can either be attached to __ or __ of RBCs.

Answer 17

glycoproteins; glycolipids

Question 18

T/F. Saliva can always be used as a substitute for blood typing because ABO antigens can also be found in secretions.

Answer 18

False. Not everyone is a secretor, or those whose ABO antigens exist in water-soluble forms

Question 19

The ABO antigens may exist in free form and manifest themselves in bodily secretions except __

Answer 19

Cerebrospinal fluid

Question 20

T/F. There is no correlation between ABO phenotype and blood clotting.

Answer 20

False. Blood group O have 25% less FVIII and vWF in their plasma

Question 21

How many known antigens are there for the Rh blood group system? What are the five most important?

Answer 21

49; D, C, c, E, e

Question 22

What does having the Rh factor imply?

Answer 22

Having the D antigen; not having the Rh factor (negative) means you don’t have the D antigen

Question 23

The antigens involved in the Rh blood group system are __ while those of the ABO system are __.

Answer 23

proteins; oligosaccharides

Question 24

Two genes that encode for the Rh blood type. They are located in chromosome __.

Answer 24

RHD and RHCE; chromosome 1

Question 25

How does the D/d polymorphism arise?

Answer 25

Through a deletion of the entire RHD gene

Question 26

The C/c polymorphism arises from what?

Answer 26

Four SNPs in the RHCE gene, one of which determines the C or c antigen specificity

Question 27

How does the E/e polymorphism arise?

Answer 27

Single SNP in the RHCE gene

Question 28

T/F. RHCE protein is a transmembrane multipass protein while RHD isn’t.

Answer 28

False. They are both transmembrane multipass proteins.

Question 29

T/F. Rh proteins are not glycosylated.

Answer 29

True.

Question 30

What are the functions of the Rh proteins?

Answer 30

Maintenance of membrane integrity - loss of which may cause mild hemolytic anemia
Involved in the transport of ammonium across the RBC membrane

Question 31

Hemolysis in Rh incompatibility is (intra-/extra-)vascular.

Answer 31

extravascular

Question 32

What is the severity of having:
Anti-D antibodies?
Anti-c antibodies?
Anti-C antibodies?
Anti-E antibodies?
Anti-e antibodies?

Answer 32

Anti-D and -c can cause severe diseases

Anti-C, -E, and -e can cause mild to moderate disease.

Question 33

T/F. Blood antigens can only be found in RBCs.

Answer 33

False. HLAs.

Question 34

Loci of HLA

Answer 34

Chromosome 6

Question 35

HLA genes are divided into:

Answer 35

Class I (HLA A, B, C) and Class II (HLA DP, DM, DOA, DOB, DQ, DR)

Question 36

T/F. HLA genes are polymorphic, polygenic, and co-dominant.

Answer 36

True.

Question 37

Class of MHC that presents peptide remnants to cytotoxic T cells; those recognized as foreign will be induced to apoptose.

Answer 37

Class I

Question 38

Class of MHC that binds peptides derived from extracellular proteins, peptides are presented to helper T cells

Answer 38

Class II

Question 39

Happens when T cells bind to non-self MHCs

Answer 39

Cross-reactivity

Question 40

Two ways that cross-reactivity occurs

Answer 40

Peptide-dominant binding

MHC-dominant binding

Question 41

T/F. GVHD is when the body rejects the transplanted tissue.

Answer 41

GVHD happens when the transplanted tissue is the one that rejects the body itself.

Question 42

Testing used to know the histocompatibility of transplants. It uses sera that contain specific antibodies to HLA antigens.

Answer 42

Serologic Testing