Female Tac chromosome identification. (a) Paint Y1 covers two copies of X1p, chromosome Y1 is not present. (b) Paint Y2 covers the homology regions on two copies of X2 and X3; Y2 is not present. (c) Paint X3 hybridizes to the chromosome pair X3. (d) Paint X5 hybridized to the chromosome pair X5. (e) Tac meiotic chain configuration. Hybridization with telomeric probe confirms a chain of nine elements. (f) Paint Y4 identifies the last but one chromosome in the chain. (g) Paint X4 covers X4 and Y3, the seventh and sixth element of the chain, the chain configuration is at the right.