LRRC3 is a 257 amino acid protein that contains 3 LRR repeats. The gene encoding LRRC3 maps to chromosome 21, the smallest of the human chromosomes. Chromosome 21 contains nearly 300 genes and 47 million base pairs. Down syndrome, also known as trisomy 21, is the disease most commonly associated with chromosome 21. Translocations are found to occur between chromosome 21 and 8, and chromosome 21 and 12, in certain leukemias.