REPORT OF THE COMMITTEE ON THE GENETIC CONSTITUTION OF CHROMOSOME-10, CHROMOSOME-11, CHROMOSOME-12, CHROMOSOME-X, AND CHROMOSOME-Y

The lipase-A (LIPA) locus has been assigned to chromosome 10 by analysis of the karyotype and the chromosome 10 marker GOT 1 in human-Chinese hamster hybrids. Some individuals have a fragile site at 10q23 in a small proportion of their cells. Its frequency is enhanced when the cells are grown in medium lacking folic acid and thymidine or containing amethopterin. The assignment of GOT1 to the region 10q24→10q26.2 has been confirmed. The gene coding for human β-hemoglobin (HBB) was assigned to chromosome 11 by nucleic acid hybridization and somatic cell hybridization methods. The presence of human chromosome 11 is both necessary and sufficient for the release of murine xenotropic endogenous oncornavirus expression from hybrids of BALB/c mouse cells and human cells. The data suggest the existence of a human gene, BVIX, that is involved in oncornavirus expression. Regional assignment of seven genes on chromosome 12 has been carried out, based on both cytogenetic data and a statistical mapping analysis of their patterns of segregation in hybrid clones. The X-linkage of gene coding for phosphoribosyl pyrophosphate synthetase (PRPS) has been established by pedigree analysis in families with an altered form of the enzyme that has increased activity. The role of the human Y chromosome in sex determination leads to the conclusion that a factor determining the differentiation of the embryonic gonads into testes is located in the Y chromosome. Studies of structurally abnormal y chromosomes suggest that this factor is located in the short arm.