Question

Could somebody explain to me how DNA is lost in the termination step of DNA replication?

Answer 1

I assume you have heard the vocabulary I will use now. if not, look it up. :-)


first step (first replication):
the DNA is lost in a two-step-process. as you can imagine, the leading strand will be replicated until the matrix strand is completely copied. no problem here.

the lagging strand consists of okazaki fragments, so you have many many primers on it. as you can imagine, the outermost primer will not start on the absolutely last nucleic acid of the matrix strand, but ~80 to 300 bases before that. this means, that those 80 to 300 bases will not be transcribed, resulting in a shorter replicated strand.

thus, you will get two strands after the first replication, and one strand is longer than the other one.

second step (second replication):
the now shorter replicated strand is the matrix for the leading strand. it will be copied, and the copied strand will be ~80 to 300 bases shorter than its precursor.

the lagging strand will be copied from the longer strand. the same problem with the okazaki fragments will occur, resulting in a strand roughly the same length as the other daughter strand.

thus, you will get two strand of equal length, both being ~80 to 300 bases shorter than your original strands from two replications before that. the cacle begins anew.