Non-Mendelian behavior: linked genes. Genes A and B are located on the same chromosome. Shown here is a cross between a homozygous dominant parent and a homozygous recessive parent that results in F₁ hybrid progeny, all AaBb. Because the alleles for the two genes are close together on the same chromosome (A, B and a, b), they cannot separate during the formation of gametes. Each gamete receives one copy of this chromosome, and thus either the A and B alleles or the a and b alleles; no gametes containing A and b or a and B are formed. The two genes A and B are linked and do not assort independently during meiosis in the formation of gamete cells.