Genetics in Immunohematology – ABO & Rh Systems

Vocabulary flashcards covering essential terms and definitions from the Genetics in Immunohematology lecture.

Gene

Segment of DNA that codes for a specific protein.

Allele

Different forms of a gene (e.g., A, B, O).

Genotype

Genetic makeup (e.g., AO, BB).

Phenotype

Observable trait (e.g., blood type A, B, O).

Homozygous

Two identical alleles (e.g., AA, BB).

Heterozygous

Two different alleles (e.g., AO, BO).

Dominant

An allele that is expressed when present.

Recessive

An allele that is only expressed when two copies are present.

Codominant

Both alleles expressed equally (e.g., A and B).

ABO Gene

Controlled by ABO gene on chromosome 9.

Alleles in ABO System

Three main alleles: A, B, and O.

ABO Dominance

A and B are codominant; O is recessive.

A Antigen Addition

A adds N-acetylgalactosamine to H antigen.

B Antigen Addition

B adds galactose to H antigen.

O Antigen Function

O has no functional enzyme; H antigen unchanged.

AA or AO Genotype

Results in Phenotype Type A.

BB or BO Genotype

Results in Phenotype Type B.

AB Genotype

Results in Phenotype Type AB.

OO Genotype

Results in Phenotype Type O.

H Antigen

Precursor substance for A and B antigens.

Bombay Phenotype

Lacks H antigen; cannot form A or B even if genes present.

Rh Blood Group Genetics

Controlled by RHD and RHCE genes on chromosome 1.

D Antigen

Determines Rh positive or negative status.

Presence of RHD Gene

Indicates Rh positive blood type.

Absence of RHD Gene

Indicates Rh negative blood type.

Other Rh Antigens

Include C, c, E, and e.

Rh Inheritance

Inherited as haplotypes (e.g., DCe, dce).

Haplotype Inheritance

One haplotype comes from each parent.

D Dominance

D is dominant over absence (denoted as d).

Rh+ Genotype

Can be DD or Dd; Rh- is dd.

Example Rh Cross

Parent 1: Dd (Rh+), Parent 2: dd (Rh-), offspring 50% Rh+, 50% Rh-.

ABO Incompatibility

Can cause severe immediate hemolysis.

Rh Incompatibility

Can lead to Hemolytic Disease of the Fetus and Newborn (HDFN).

Clinical Importance of Genetics

Important for predicting inheritance patterns.

Applications of Genetics

Used in paternity testing and transfusion safety.

ABO System Key Points

A and B are codominant; O is recessive.

Universal Recipient

AB blood type is the universal recipient.

Universal Donor

O blood type is the universal donor.

H Antigen Requirement

Required for A and B expression.

Bombay Phenotype Characteristic

Lacks H antigen.

Rh D Antigen

Most important antigen in the Rh blood group.

Rh Antibody Formation

Rh antibodies form only after exposure.

Blood Genotype

The genetic combination that determines blood type.

Genetic Makeup

The set of genes that contribute to individual traits.

Observable Trait

The physical manifestation of a genotype.

Transfusion Reaction

An adverse reaction due to incompatibility.

Inheritance Patterns

The transmission of genetic traits from parents to offspring.

Immunohematology

The study of blood groups and their immune responses.

Genetic Variation

Differences in alleles among individuals.

Phenotypic Expression

The outward expression of a genotype.

Co-dominance

Situation where both alleles are fully expressed.

Chromosome 9

Location of the ABO gene.

Chromosome 1

Location of RHD and RHCE genes.

H Antigen Role

Essential for A and B antigen formation.

Blood Type Testing

Determining an individual's blood type.

Rh Factor Testing

Determining whether an individual is Rh positive or negative.

Genetic Disorders

Medical conditions caused by abnormalities in genes.

Population Genetics

The study of genetic variation within populations.

Mendelian Inheritance

Patterns of inheritance discovered by Gregor Mendel.

ABO System Importance

Critical for blood transfusion compatibility.

Rh Incompatibility Consequences

Can be severe in pregnancy.

Genetic Screening

Testing individuals for genetic disorders.

Gene Expression

The process by which information from a gene is used.

Allele Frequency

Proportion of different alleles in a population.