Final answer:
Single-stranded DNA (ssDNA) tails invade target sequences during processes such as homologous recombination or retro-transposition, or when viruses like T4 bacteriophage inject their genetic material into host cells for replication.
Step-by-step explanation:
The question is asking about the process by which single-stranded DNA (ssDNA) tails invade a target. In biological terms, ssDNA tails are often involved in the mechanisms of genetic exchange, such as homologous recombination or the process of retro-transposition, where genetic elements move within a genome. During homologous recombination, ssDNA tails can invade homologous sequences of duplex DNA to initiate repair or to facilitate genetic mixing. Retro-transposition involves ssDNA intermediates that integrate into new locations in the genome. Moreover, when discussing viruses like T4 bacteriophage, the concept of ssDNA invasion may refer to the injection of genetic material into a host cell, such as Escherichia coli, for replication and propagation of the virus.