[citation needed] Such procedures can test only the integrity of a tiny part of the overall 23 million base pair long Y chromosome.
Present diagnostic techniques can only discover certain types of deletions and mutations on a chromosome and give therefore no complete picture of genetic causes of infertility.
[citation needed] The preferred test for genetic mutation, namely complete DNA sequencing of a patient's Y chromosome, is too expensive for use in epidemiological research or clinical diagnostics.
[citation needed] In up to 20% of men with reduced sperm count, some form of YCM has been detected.
[5] Additional genes associated with spermatogenesis in men and reduced fertility upon Y chromosome deletions include RBM, DAZ, SPGY, and TSPY.