The present invention provides for a method for isolating and partially characterizing the nucleotide sequence for a novel polypeptide chain of human basement membrane (type IV) collagen, referred to as the .alpha.5(IV) polypeptide chain. The invention provides for the use of the identified nucleotide sequence (or DNA fragments thereof) to detect mutations in individual genes specific for the .alpha.5(IV) chain which can, directly or indirectly, produce several human diseases. Moreover, the invention also relates to procedures for determining genetic or acquired disorders of basement membranes using the identified nucleotide sequence (or DNA fragments thereof) of the .alpha.5(IV) polypeptide chain, probes specific to DNA fragments of said nucleotide sequence,or antibodies to the nucleotide sequence or DNA parts thereof. Also, the invention relates to the use of gene fragments generated through amplification from human genomic or cloned DNA for detection and analysis of the gene, such as in detection of mutations.