Genetics for Blood Bank Flashcards
blood group genetics
- antigen’s structure & location on RBC
- antibodies they elicit
- genetically defined
- serologically defined
genes
basic units of inheritance that encode for certain traits or visible characteristics
chromosomes
double strands of DNA that contain genetic information
mitosis
cell division of somatic cells - 2N daughter cells
Meiosis
cell division of gametes that result in 4 1N cells
Mendelian genetics
each parent contributes half of their genes to their offspring
Punnett squares
illustrates the probabilities of phenotypes from known or inferred genotypes
loci
specific locations on chromosomes where genes are located
alleles
different forms of the same gene & may exist for each locus
polymorphic
refers to a genetic system that expresses 2+ phenotypes (ABO system & HLA system)
antithetical
‘opposite’ refers to antigens encoded by alleles at the same locus where you can have either one antigen or the other, not both
ex: Kell system
amorphs
silent genes that do not produce a detectable antigen due to gene structural changes (deletions or frameshifts)
ABO amorph - O type
suppressor gene
inhibits the expression of another gene and can lead to a null phenotype
codominant
equal expression of genes
ex: A type & B type = AB
Gene dosage effects
if an individual is homozygous they will have a higher antigen expression and therefore a greater agglutination reaction
law of independent assortment
different antigens, inherited on different chromosomes are expressed & inherited independently of each other
ABO on chromosome 9
haplotype
genes that are inherited together
ex: Rh system, MNS, H
cis genes
inherited on the same chromosome
trans genes
inherited on the opposite chromosome
HLA haplotypes
HLA-A & HLA-B are linked
highly polymorphic!
Calculation of Gene Frequencies
probability of finding a unit negative for specific antigens should patient have multiple antibodies
- find gene frequencies for NEGATIVE antigens
- multiply frequencies to find fraction of negative units
- take inverse to see how many units should be scanned
Direct exclusion
child has traits that neither parent has
indirect exclusion
child lacks marker father should have transmitted to all his offspring
