Leading and lagging strands?

[hivesaeed4]

I'm confused regarding one aspect concerning the leading and the lagging strands. Are they the strands which were present before replication occurs (i.e. the original/parent strands) or are they the strands which come into being after replication is completed (i.e. the newly synthesized/daughter strands).

Note:- I understand the 5' to 3' and vice versa distinctions/definitions of the two so don't explain in terms of that.

 

[atyy]

Usually the daughter strands (but the terminology is not so fixed that you can't say "leading strand replication" or "leading parent strand" or "leading template strand").

http://www.ncbi.nlm.nih.gov/books/NBK26850/ (Fig. 5.8)
http://www.ncbi.nlm.nih.gov/books/NBK21751/ (Fig. 12.9)

 

[Ygggdrasil]

As atyy said, "leading" and "lagging" refer to the daughter strands. This is in part because the parent strand can template both leading and lagging strand synthesis. For example, consider a replication bubble. On the side of the bubble, the left side of the bubble, the top parent strand acts as the template for leading strand synthesis while on the right, the same parent strand acts as the template for lagging strand synthesis.

 

[hivesaeed4]

That cleared up any confusion I had. Thanks.

 

[LudusRex]

The leading and lagging strands refer to the two strands of DNA that are synthesized during replication. The leading strand is the one that is continuously synthesized in the 5' to 3' direction, while the lagging strand is synthesized in small fragments in the opposite direction and then joined together to form a continuous strand.

To answer your question, the leading and lagging strands are both present before replication occurs, as they are part of the original parent DNA. However, during replication, the leading strand is the first to be replicated and serves as a template for the synthesis of the lagging strand. So, in a way, the leading strand can be seen as the "older" parent strand, while the lagging strand is the "newly synthesized" daughter strand.

I hope this clarifies any confusion you had regarding the leading and lagging strands. It's important to remember that both strands are essential for DNA replication and play different roles in the process.