Lecture 13. Genetics in Bloodbanking

What are blood group systems?

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

DNA is contained in

Chromosomes

Genetic material is replicated either by _____ or _____

Mitosis/Meiosis

Phenotype

Physical expression of traits (what is observed)

Genotype

Actual genetic makeup (not directly observed)

A person with the phenotype A could have the genotype:

A/A or A/O

Allele

Variant form of a gene at a specific location of a chromosome

A Punnett square predicts:

The probability of an offspring’s genotype

Each person inherits one allele from:

Each parent

Antithetical Antigens

Opposite versions of a blood group antigen

Kp^a and Kp^b antigens are examples of:

Antithetical antigens

ABO do NOT have antithetical antigens (involves codominance, not simple opposite pairs)

True

• K and k,

• Kp^a and Kp^b

• Js^a and Js^b

These pairs belong to the:

Kell Blood Group System

• C and c,

• E and e

These pairs belong to the:

Rh Blood Group System

Fy^a and Fy^b belong to the:

Duffy Blood Group System

Jk^a and Jk^b belong to the:

Kidd Blood Group System

• M and N,

• S and s

These belong to the:

MNS Blood Group System

Lu^a and Lu^b belong to the:

Lutheran Blood Group system

Recessive gene

Is expressed only when inherited by both parents

Codominant gene

Equal expression of two different alleles

Blood group antigens are

Codominant

Dominant gene

Gene that is expressed over another gene

Genes that do not express a detectable product are considered

Amorphic (O gene)

Mendelian principles apply to:

Blood group antigen inheritance

Independent segregation

Each parent passes one gene to the offspring

Independent assortment

Blood group antigens on different chromosomes are inherited separately, creating genetic variation

Linkage

When two genes close together on a chromosome are inherited together

Crossing over happens when:

Two genes on the same chromosome exchange segments

Homozygous occurs when:

A person inherits two identical alleles

MM (M+ N-) is an example of

Homozygous alleles

Heterozygous allele

A person inherits two different alleles

MN (M+ N+) is an example of:

Heterozygous alleles

When it comes to a dosage of antigens, people who have homozygous alleles:

Have a “double dose” of an antigen because they inherited two identical alleles

When it comes to a dosage of antigens, people who have heterozygous alleles:

Have a “single dose” of an antigen because they inherited two different alleles

Cell #1 likely contains

Homozygous c alleles

Cell #2 likely has”

Heterozygous C and c alleles

Phenotype calculation is used to:

Determine the likelihood of finding RBC units with specific antigen characteristics

The Phenotype calculation is particularly useful in:

Identifying antigen-negative blood for patients with alloantibodies

Hardy-Weinberg formula

An equation used to determine gene frequencies that contribute to a trait in a population

A patient with multiple antibodies (anti-C, anti-E, anti-S) needs blood, when all three positive results are multiplied, it comes out to 10%. What does this mean for finding someone who would be compatible for the patient?

Only 10% of the population will be negative for all three antigens; about 1 in 10 units will be compatible