Question

Why is DNA replication called semiconservative?

Answer 1

 
Hint: DNA replication is the process of production of two replicas of DNA from one original parent DNA molecule and this is the principle process for biological inheritance. During DNA replication the strands formed in the new molecule are complementary with new strands formed in antiparallel fashion against one of the original template strands.

Complete step by step answer:
DNA has a double- helical structure. For DNA replication, the parent DNA molecule is first spliced using the helicase enzyme to separate the two strands of DNA. Each of the separated strands is then used as a template to synthesize a new daughter DNA strand. Thus, in a new daughter DNA molecule, one half of it, i.e., one of the strands in the daughter molecule is the parent strand and the other strand is newly synthesized. Since, one parent strand is conserved in each new molecule, this type of replication is known as the semiconservative type of DNA replication.

Additional Information: DNA replication takes place in three major steps.
- Opening of the DNA double helix and separation of the strands - Priming of template strands - Assembly of DNA segments that are newly formed
Enzymes play a very important role in DNA replication. The main enzymes that take part in DNA replication are:
- Helicase: It is the enzyme that splices or splits the parent DNA to form two template strands. This splitting occurs at a specific point called the origin.
- DNA Primase: They are enzymes that attach short RNA primers that are short RNA sequences, to the strands in the replication fork to begin the process of DNA replication.
- DNA Polymerases: They are the prime enzymes that are responsible for DNA replication and add the nucleotides one by one and thus increasing the length of the daughter strands. There is more than one type of DNA polymerase used in the process of DNA replication.
- DNA ligases: It joins the DNA strands together by forming phosphodiester bonds.
- Topoisomerase: They release the topological stress formed due to the process of replication. They splice one end of the strand and move around the other and re- join the strand.

Note:  There are other models of DNA replication other than the semiconservative model called the conservative model and dispersive model.
- In the conservative model of DNA replication, the parental DNA molecule directs the synthesis of an entirely new DNA molecule, such that after one round of replication, one molecule is conserved as it has two old strands and this is repeated in the second round too.
- In the dispersive model the material in the two parental strands gets distributed more or less randomly between the two daughter molecules. Thus, there can be similarities between the parent and daughter molecule, but there are no strands that are 100 percent similar to the parent strand.