Question

1. What is a "Parasitic Chromosome" and how is it different from an ordinary chromosome? Give an example.

2. What is a Homing Endonuclease and how are they named?

Answer 1

1. Chromosomes that spread throughout cell divisions, even if they have no advantages to the overall organism's existence is known as parasitic chromosome. It is a selfish chromosome, it can continue even if slightly harmful to existence, as is features of some selfish genetic element.
Parasitic chromosome they are not necessarily present in the majority of the species population but the ordinary chromosome present in majority of the species and parasitic chromosome are not needed for basic life functions, in the contrast to ordinary chromosome.
An example of a parasitic chromosome is the b24 chromosome.

2. The homing endonucleases are a collection of endonucleases. They catalyse the hydrolysis of genomic DNA within the cells that synthesize them, but do so at very few, or even singular, locations. The homing endonuclease encoded either as freestanding genes within introns, as fusions with host proteins, or as self-splicing inteins. Repair of the hydrolyzed DNA by the host cell frequently results in the gene encoding the homing endonuclease having been copied into the cleavage site, hence the term homing to describe the movement of these genes.Homing endonucleases are always indicated with a prefix that identifies their genomic origin, followed by a hyphen: "I-" for homing endonucleases encoded within an intron, "PI-" (for protein insert) for those encoded within an intein.