RHD zygosity determination

Fig. 1 Genomic organization of the RH locus in RhD-positive and RhD-negative chromosomes. Arrows indicate polymorphic sites used for RH genotyping. SNPs in RHD exons 1-7 and 9 are also detected in some RHD genotyping strategies.

of 109 bp in intron 2, 288 bp in intron 3, and 651 bp in the very short intron 4 have been reported.[2,3,5,7]

The physical distance between RHD and RHCE is approximately 30,000 bp, and it is filled with a Rhesus box and the SMP1 gene. The two RH genes have opposite orientations and face each other with their 3' ends. Considering this chromosomal organization, the lack of the RHD gene in most RhD-negative Caucasians was probable because of an unequal crossing-over event between two highly homologous DNA segments termed Rhesus boxes, which flank either side of the RHD gene, resulting in the formation of a hybrid Rhesus box. The analysis of the hybrid Rhesus box would be a predictor of RHD zygosity.[8] One copy of the hybrid Rhesus box predicts a heterozygous RHD-positive genome (Fig. 1).


segments that may disrupt the secondary or tertiary structure, or may alter the optimal membrane integra-

It is important to note that there also exist unexpressed RHD alleles in RhD-negative phenotypes. These RHD-positive antigen D-negative alleles are most frequently found in non-Caucasian populations and are rare in whites. In Africans, the major RHD-negative allele is a RHD pseudogene designated RHDC.[11]

The RHCE gene also bears its own heterogeneity, which is responsible for C, c, E, and e polymorphisms. RHC and RHc alleles differ in one nucleotide in exon 1 and in five nucleotides in exon 2, whereas RHE and RHe have a difference of a single nucleotide in exon 5.[2,3,5,7] Different RHCE rare alleles are responsible for depressed, partial, or ablated expression of C/c and/or E/e anti-gens.[9,10]

Besides the most common RHD DNA sequence, several allelic RHD variants are responsible for partial D phenotypes, weak D phenotypes, or unexpressed RhD pro-teins.[9,10]

Molecular alterations in partial D phenotypes generally affect at least one extrafacial amino acid. On the contrary, molecular studies of weak D phenotypes have shown that weak D alleles lead to aberrant RhD proteins with amino acid substitutions in transmembranous and intracellular

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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