IB 169: Case 2 O Blood Type

Human Blood Type Alleles

-3 blood type alleles: A, B, O -Each human has 2 of these alleles -A or B are each dominant over O which is recessive but neither A or B are dominant over each other -When both A and B alleles (blood type AB) occur together they are CO-DOMINANT

AB Genotype

-A person with AB genotype is NOT capable of making antiA or antiB Ab and can receive blood from any of the genotypes -People with AB genotype (AB phenotype) are UNIVERSAL RECIPIENTS

Maternal Exposure to Fetal RBCs During Pregnancy

-A small number of fetal RBCs CROSS the PLACENTA and enter the mom's blood during 2nd and 3rd trimester

Case 2: Why was O type/phenotype blood in low supply?

-All 3 blood type alleles (A,B, O) are present in contemporary CA human populations which are made up predom of people whose ancestors originated from Latin America, Europe, Asia, Africa, and Oceania in addition to a small percentage of Native CA Indiatns -A and B are dominant -O is RECESSIVE -Blood type O is much LESS COMMON than blood types A or B in contemp CA populations, hence supply of type O is less

Human Migration to the Americas

-At least 20,000 yrs ago the migration into the Americas occurred -1 or more migrations by relatively small groups of SIBERIAN HUMANS over the landmass called BERINGIA which connected present day Siberia and Alaska between 20,000-8,000 yrs ago because of the fallen ocean level during the last glacial period -As the N. Amer glaciers began to melt and recede about 20,000 yrs ago, the way for southward migration was opened and H. Sapiens reached southern. S. Amer as early as 14,000 yrs ago -An example of the LOW GENETIC DIVERISTY in Native Americans is the fact that nearly ALL have blood phenotype O/genotype OO (esp western USA, Mexico, C Amer, and S Amer Indians) with a very LOW FREQUENCY of blood type A and B

Bottlenecks, Founder Effects, and Subsequent Population Growth

-BOTTLENECK generated a SMALL POPULATION compared to original source population size -This small population tended to be influenced by GENETIC DRIFT but could have also been influenced by NATURAL SELECTION, however, there was NOT LIKELY a significant selective force for the O allele over the A or B alleles

Case 2:Chumash Indian Patient Outcome

-Because no O type blood was available, this male was immediately given fluids to maintain his blood pressure -Soon after his arrival into the ER, 2 of his sisters arrived and both had their blood immediately typed and both were O type/phenotype -Blood was donated at that time from his sisters and he was given a transfusion of fresh O type/phenotype blood -He recovered from his injuries and was discharged to go home 3 days later

Blood Phenotype B

-Blood group B is highest frequency in NORTHERN INDIA AND CENTRAL ASIA -Believed to be entirely ABSENT from NAT AMER & AUSTRALIAN ABORIGINALS populations prior to the arrival of Europeans -Today, frequency of type B blood allele in Native Amer is 4%, even though type B blood is significantly more common in the Asian population from where the Native Americans migrated

Influence of Blood Type/Phenotype Expression by Interaction of 2 Dom Alleles (A and B) with 1 Rec Allele (O)

-Both A and B allele MASK the rec O allele so frequency of O blood type/phenotype in the contemp CA human pop is much lower than the O allele frequency in the population -O blood is the UNIVERSAL DONOR -These features contribute to the relatively LOW SUPPLY of O blood type/phenotype in CA today -The supply of donor blood is further limited for people with O blood type/phenotype because they are universal donors and can ONLY receive O blood

Antibodies of ABO System

-Depending on blood type, they may develop anti-A antibodies, anti-B antibodies or none -Anti O Ab are NOT formed by humans -Persons with genotype AA, AO, or OO will form antiB Ab if they are exposed to blood from a person with a BB, AB, or BO genotype causing them to reject the blood -Genotype BB, BO, or OO will form anti-A Ab if they are exposed to blood from a person with AA, AB, or AO, causing them to reject the blood -Genotype OO form both antiA and antiB Ab when exposed to both A and B alleles -Genotype AB: no Ab

Maternal-Fetal ABO Blood Group Incompatbility

-Humans may be blood group A, B, AB, or O -Group O is universal donor and group AB is universal recipient -If mom is blood O conceives a fetus that is A or B, a small amount of fetal blood cells can leak into maternal blood circulation -The group O mom may develop antiA/B IgG Ab to fetal blood antigens -Maternal antiA/B IgG Ab can then pass thru the placenta into the fetal circulation and cause DESTRUCTION OF FETAL RBCs which can result in ELEVATED BILIRUBIN -ABO maternal-fetal blood group incompatibility typically results in significantly LESS SEVERE effects on the fetus/infant compared to RH INCOMPATABILITY

O Allele and Protection Against Plasmodium Falciparaum

-It has been suggested that the O allele protects against severe malaria -Common variation in the ABO GLYCOSYLTRANSFERASE is associated with susceptibility to severe Plasmodium falciparum malaria -Since malaria was not present in the Americas when H. Sapiens migrated in, there would NOT have been a selective advantage for this allele

Genetic Drift

-LARGE populations: in the absence of selection, allele frequencies tend to change SLOWLY over generations -SMALL populations: in the absence of selection, the STOCHASTIC nature of reproductive processes means that alleles may be lost (0% freq in pop) or fixed (100% freq in pop) within a FEW GENERATIONS

O Allele and Susceptible to Heliobacter pylori Infections

-O allele is more susceptible to HELIOBACTER PYLORI infections -Attachment of Heliobacter pylori to HUMAN GASTRIC EPITHELIUM mediated by blood group antigens

O allele and Cholera Susceptibility

-O allele is more susceptible to severe forms of cholera infections -Severe life-threatening cholera associated with blood group O in PERU: implications for the LATIN AMERICAN EPIDEMIC -The higher rates of the B allele in Northern India give people more protection against cholera

ABO Alleles and Disease Susceptibility

-O allele is more susceptible to the BUBONIC PLAGUE -A allele is more susceptible to SMALL POX -May account for the incr freq of the B allele in CHINA, INDIA, & PARTS OF RUSSIA which suffered epidemics of both of these diseases

OO Genotype

-OO genotype can make BOTH ANTI-A or ANTI- B Ab and therefore can NOT receive AA, BB, AB, AO, or BO genotype blood because it will be rejected -OO genotype can ONLY receive blood from a person with OO genotype -OO genotype (O phenotype) are UNIVERSAL DONORS because Ab are not formed against O by A, B, AB, or O

Acute Hemolytic Reaction

-Occurs during REJECTION of blood transfusion because of ABO blood type mismatch -Type O blood recipient will reject any blood type (A, B, AB) other than type O -Type B blood recipient will reject A and AB -Type A will reject blood B and AB -Type AB will accept all blood types (univ recipient)

Case 2: Blood types

-Only blood available was A, AB, and B blood types (phenotypes) -This Native Amer Chumash male is O phenotype and can only receive O -Chumash Indian ancestral distribution is along the COAST in SOUTHERN CA

Native Amer Founder Population

-POPULATION BOTTLENECKS from migration of small groups from the original population have resulted in FOUNDER EFFECTS which have caused a HIGH LEVEL OF GENETIC HOMOGENEITY in Nat. Amer in N. Amer, Mexico, C Amer, and S Amer -Some scientists suggest that the original founder population in the Americas may have been 70 or fewer individuals -Amerindians are found to mostly have blood phenotype (genotype OO); this high frequency of blood type O is thought to be due to a genetic bottleneck that generated a founder effect

Human Blood Transfusions

-RELATIVELY RECENT in human history -In relationship to blood transfusions, the disadvantage that people with Type O blood phenotypes have and the advantage that Type AB blood phenotypes have are recent in human history and are NOT traits that have been influenced by SELECTION

ABO System

-The most important blood-group system in determining appropriate donors and recipients for human-blood transfusions -Transmitted through MONOGENIC INHERITANCE -Humans have the same blood type phenotype (characteristic) but diff genotypes (gene sequences) -3 blood type alleles: A, B, O -Each human has 2 of these alleles -A or B each dominant over O which is recessive, but neither A or B are dominant over each other -6 possible genotypes: AA, AO, BB, BO, AB, OO -4 blood types/phenotypes: A, B, AB, O

Case 2: Adult Male from Chumash Indian Tribe with O blood type in Emergent Need of Blood Transfusion

-This 30 yr old Chumash Indian male was injured in a car accident and arrives by ambulance to the ER of a small hospital in CA -Due to multiple lacerations, he has lost a fair amt of blood and his bp is 40/90 which is dangerously low -He needs a blood transfusion emergently -He is O phenotype blood -Unfortunately, there is no O type blood available in this hospital.

Bottleneck

A dramatic REDUCTION in POPULATION SIZE due to MIGRATION of a small population from the original population in Asia

ABO Phenotypes and Genotypes

AA genotype: phenotype A BB genotype: phenotype B AB genotype: phenotype AB (UNIVERSAL RECIPIENT) AO genotype: phenotype A BO genotype: phenotype B OO genotype: phenotype O (UNIVERSAL DONOR)

Dominant Allele

An allele that masks the other allele

Human Blood Types

BLOOD TYPE/BLOOD GROUP: A classification of blood based on the presence or absence of INHERITED ANTIGENIC SUBSTANCES on the surface of RBC -These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system -Blood types are inherited and represent contributions from both parents -A total of 30 human blood group systems are now recognized by the International Society of Blood Transfusion

Co-Dominant Alleles

Both alleles are expressed -e.g. blood type AB

What parental genotype(s) generate a blood phenotype O in all offspring?

Both parents need to be homozygous for OO for all offspring to be genotype OO and O blood type/phenotype

Mendelian Monogentic Inheritance: Homozygous vs Heterozygous

HOMOZYGOUS: the pair of alleles at a locus are identical HETEROZYGOUS: the pair of alleles at a locus are different A population of organisms within a species may include multiple alleles at the locus among various individuals -ALLELIC VARIATION at a locus is measurable as the number of DIFFERENT alleles present, or the PROPORTION OF HETEROZYGOTES at that LOCUS in the population

What was the evolutionary pathway responsible for the high amt of O blood type phenotype in Native Amers?

Human MIGRATION to the Americas

Blood Phenotype B has Some Protection Against Cholera

It is believed that the high frequency of blood phenotype B in NORTHERN INDIA along the GANGES RIVER BASIN is because it was positively selected for since it offers protection against CHOLERA DIARRHEA

What genotype(s) generate(s) a blood phenotype O?

OO genotype generates a blood phenotype O

Evol Pathway Responsible for the High Amount of O Blood Type Phenotype in Native Americans

Outcome of DEMOGRAPHIC HISTORY Migration of small population producing a BOTTLENECK which generated in a FOUNDER EFFECT which resulted in the high blood O allele frequency in the population which was likely fixed through DRIFT

Recessive Allele

The allele that is masked

Why is This Native Amer Chumash O blood type/phenotype and OO genotype?

The distribution of O blood phenotype in native populations is HIGHEST in the WEST COAST OF AMERICAS -AFRICA, RUSSIA

Founder Effect

The principle that the founders of a SMALL NEW POPULATION generated by a bottleneck, carry only a FRACTION of the TOTAL GENETIC VARIATION in the original larger source population

Blood Types in the USA

Type A: 42% Type B: 10% Type AB: 4% (universal recipient) Type O: 44% (universal donor)