Hi,

This might be an interesting read for you (for me it was):

doi: 10.1016/S0921-8777(99)00017-8

Cheers,

Lech

That is ok. But, here, the question is what are the advantages of linear DNA over circular DNA. Why linear DNA is selected in higher organisms in evolutionary process?

My (un)educated guess would be that (as DNA of eukaryots is much longer) in a linear form it is more easy to physically manipulate it (e.g. wrap and unwrap of histones, condense during mitosis, align homologous chromosomes, etc.). If you have a long tangled thread, is it easier for you to untangle it when the ends are connected, or when they are not?

Cheers,

Lech

Thank you Dr. Lech Kaczmarczyk for the reference. Nice article and nice arguments. Could be the possible explanation to my doubts. Thank you.

Here I am quoting it...  Any one interested, please read it..

"A loopy view of telomere evolution" Titia de Lange

"WHY LINEAR CHROMOSOMES?

Before the linear chromosomes of eukaryotes emerged 1 Gy ago, circular chromosomes had been

successfully used for 2 Gy and they continue to predominate in the most common organisms on this

planet (eubacteria and archaea). What were the disadvantages of circular chromosomes that could

have ensured the supremacy of an incipient eukaryote with linear chromosomes?

It has been suggested that the answer lies in the first division of meiosis (Ishikawa and Naito,

1999). Meiosis may have first evolved as a mechanism to correct polyploidy arising from genome

segregation mistakes. Furthermore, the counterpart of meiosis, the syngamic fusion of haploid

cells to form diploids may have been advantageous to survive famine as well as providing greater

resistance to the highly mutagenic environment that existed 1 Gy ago. It was argued that switching

between diploid and haploid states poses a problem for organisms with circular chromosomes.

In the reductional division of meiosis, the homologous chromosomes are held together by their

chiasmata where recombination has generated a crossover between homologous chromatids. A single

meiotic crossover (or any uneven number of crossovers) generates a dicentric circle, which will lead

to non-disjunction of the homologs. As this problem is circumvented with linear chromosomes,

linearization may have provided a selective advantage.

This argument ignores systems like the bacterial XerD/C resolution machinery, which efficiently

cuts dimeric circular chromosomes at specific dif sites (Barre et al., 2001). A similar system could

have been used to resolve dimeric circles in the meiosis of early eukaryotes. Below I propose that

linear chromosomes arose as the consequence of the invasion of a circular genome with repeat

sequences. Once formed, linear chromosomes may have had advantages under certain circumstances

but their raison d’etre, I argue, is found in the way linear DNAs with repetitive sequences at their

termini escape re-circularization through ligation."