Genetics of the C 3 System

Abstract

The C 3 types were determined in 56 Norwegian families with 172 children and in 1,220 Norwegian mother/child combinations. No exceptions from the rules of inheritance were observed. Variant C 3 types was seen in 3 families. The inheritance of the two common C 3 proteins was studied in a compiled family material comprising 152 Caucasian American, German, and Norwegian families with 376 children. No deviations from a normal inheritance pattern were observed. The present study revealed no indication of association between C 3 types and phenotypes within the ABO, Rh, MN, Hp, Gc or PGM₁ systems.

Application of the C3 System in Paternity Cases

“…The results are found in table I. The estimations were based on a compilation of the family and mother-child materials reported from the USA [6], Germany [11] and Norway [25]. The total material comprises only individuals of Caucasian extraction.…”

“…This level is satisfactory and should allow the introduction of the system in practical work on paternity cases. An increase in the genetic reference material would, nevertheless, be valuable, especially since a silent allele has been described in this system [4], In an earlier paper [25], it was concluded that most of the C 3 variants so far described can be used as genetic markers in paternity cases.…”

“…The inheritance pattern of the two common molecular forms of C 3 has in this country been studied in 53 families with 161 children and in 1,197 mother-child combinations [25]. No exception to the rules of inheri tance was observed.…”

“…One apparent exception to a regular inheritance pattern has been reported, and was shown most likely to be caused by a silent allele [4]. Studies of several C 3 variants indicate that these are inherited in an auto somal codominant way like the common C 3 proteins [3,6,17,20,22,25], It has been shown that the human embryo synthesizes C 3 at 4-5 weeks gestation [10]. At birth, the C 3 content of the blood is about 50-70% of that of adults, and it increases rapidly towards adult levels during the first months of life [9].…”