SAT2400
Oct14-10, 01:46 AM
1. The problem statement, all variables and given/known data
If life had been "intelligently" design, and if an important design principle is conservation of material and efficiency of process, we would not expect DNA replication to involve the crazy, complex, intricate, Byzantine mechanism for lagging strand synthesis. For example, one way to design the process is to have both strands continuously synthesized. However, evolution is responsible for producing the lagging-strand synthesis mechanism, and evolution is notoriously constrained by ancestry. That is, because evolution works by modifying parts and processes that existed previously in an ancestor, what can exist in the descendent is limited by what existed previously. In general, evolutionary biologists call this "constraint" or "phylogenetic constraint" What is the major constraint that was likely involved in the evolution of the lagging-strand synthesis mechanism? (That is, what was the constraint most likely involved in limiting continuous polymerization to occur on only one strand at the replication fork?)
A. An RNA primer is required to start polymerization.
B. The DNA has to be unwound by a helicase, and this unwinding occurs in one rotational direction.
C. DNA polymerases only attach nucleotide monomers to the 3' end of the molecule.
D. The density of single-stranded binding proteins differs between the two strands.
E. Nucleotides have a particular polarity, with a phosphate at the 5' end and a 3' hydroxyl at the 3' end.
2. Relevant equations
Biology,,,gene replication?
3. The attempt at a solution
I think it's C..because 3' end is the part that should be open?!
Please helP~! thanks!
If life had been "intelligently" design, and if an important design principle is conservation of material and efficiency of process, we would not expect DNA replication to involve the crazy, complex, intricate, Byzantine mechanism for lagging strand synthesis. For example, one way to design the process is to have both strands continuously synthesized. However, evolution is responsible for producing the lagging-strand synthesis mechanism, and evolution is notoriously constrained by ancestry. That is, because evolution works by modifying parts and processes that existed previously in an ancestor, what can exist in the descendent is limited by what existed previously. In general, evolutionary biologists call this "constraint" or "phylogenetic constraint" What is the major constraint that was likely involved in the evolution of the lagging-strand synthesis mechanism? (That is, what was the constraint most likely involved in limiting continuous polymerization to occur on only one strand at the replication fork?)
A. An RNA primer is required to start polymerization.
B. The DNA has to be unwound by a helicase, and this unwinding occurs in one rotational direction.
C. DNA polymerases only attach nucleotide monomers to the 3' end of the molecule.
D. The density of single-stranded binding proteins differs between the two strands.
E. Nucleotides have a particular polarity, with a phosphate at the 5' end and a 3' hydroxyl at the 3' end.
2. Relevant equations
Biology,,,gene replication?
3. The attempt at a solution
I think it's C..because 3' end is the part that should be open?!
Please helP~! thanks!