Practice question

Human male karyotype 46,XY contains 22 autosome pairs plus X and Y which are largely nonhomologous aside small pseudoautosomal regions PAR1 PAR2 at tips. Genes outside PAR on X never recombine with Y genes, and Y genes unique to Y chromosome transmitted father to son. Thus X genes form one linkage group and Y genes form separate linkage group distinct from autosomes. Calculation 22 autosomes plus X plus Y equals 24 linkage groups. Exception demonstrates linkage group reflects distinct chromosome types rather than simple haploid number when heterogametic.