Interaction between the autosomal recessive bar gene and the Y-linked snakeskin body (Ssb) pattern gene in the guppy, Poecilia reticulata

Many color varieties of the guppy, Poecilia reticulata, are commercially cu ltured in Singapore for the aquarium industry. In the group of guppy variet ies called Snakeskin, males characteristically have snakeskin-like reticula tions on the body and caudal fin. The snakeskin pattern on the body of male Snakeskin guppies is due to a Y-linked gene (Ssb). Female guppies, being h omogametic (XX), do not carry the Ssb gene. About 90% of Yellow Snakeskin m ales have the typical snakeskin pattern on their bodies and tails. The rema ining males are different in that the snakeskin body pattern has been modif ied into four or five vertical bars on the caudal-peduncle region. F-1 and F-2 results of single-pair reciprocal matings of the Yellow Snakeskin varie ty show that a single gene is responsible for the vertical bar pattern. Thi s gene, bar, is autosomal recessive. In the homozygous condition (barbar), it interacts with the Y-linked Ssb gene to give vertical barring patterns o n the caudal-peduncle of Yellow Snakeskin males. This pattern is not expres sed when the dominant allele, bar(+), is present.