Genome size and organization in the blacklegged tick,Ixodes scapularisand the Southern cattle tick,Boophilus microplus.

Genome sizes and the organization of repetitive DNA were determined in the hard ticksIxodes scapularisandBoophilus microplususing reassociation kinetics. TheI. scapularisgenome contains∼2.15 pg (2.1 × 10³ Mbp) of DNA and consists of no foldback (FB), 27% highly repetitive (HR), 39% moderately repetitive (MR), and 34% unique DNA. TheB. microplusgenome contains 7.5 pg (7.1 × 10³ Mbp) DNA, and consists of 0.82% FB, 31% HR, 38% MR, and 30% unique DNA. In both species, repetitive sequences occur in a mixture of long and short period interspersion but most (65–80%) of the DNA follows a pattern of short period interspersion. Genome size and organization in the three tick species so far examined are distinct from other arthropods in having a greater proportion of MR, a lower proportion of unique and HR DNA of very low sequence complexity. [ABSTRACT FROM AUTHOR]