why is DNA semi-conservative?
does it have something to do with two new strands are formed using the two molecules from the original DNA
DNA is double strand, during transcription, they (the parents or original strands) separate into two single strands. Then the new strand will attach to each of the parent strand and form a new DNA molecule and because this new molecule consist half the parent and half the new strand, that's why it is semi-conservative.
i did this today, but didn't understand it... now i do! thank you
Yes, the semi-conservative nature of DNA refers to the fact that when DNA replicates, each new double-stranded DNA molecule contains one original ("old") strand and one newly synthesized ("new") strand. This process ensures the preservation and accurate transfer of genetic information from one generation to the next.
The semi-conservative replication of DNA was first demonstrated by the famous Meselson-Stahl experiment in 1958. Here's a step-by-step explanation of why DNA is semi-conservative:
1. DNA replication begins with the unwinding of the double helix structure of the DNA molecule.
2. Enzymes called DNA helicases break the hydrogen bonds holding the two strands together, creating a replication fork.
3. Each separated strand serves as a template for the synthesis of a new complementary strand.
4. The enzyme DNA polymerase adds nucleotides to the growing DNA strand, following the base-pairing rules (A with T, and C with G).
5. One strand serves as the leading strand, where replication proceeds continuously towards the replication fork.
6. The other strand, known as the lagging strand, is synthesized discontinuously in short sections called Okazaki fragments.
7. The enzyme DNA ligase joins the Okazaki fragments together, creating a continuous new strand.
8. Once replication is complete, each resulting double helix consists of one original strand and one newly synthesized complementary strand.
This semi-conservative replication process ensures that the genetic information encoded in the original DNA molecule is faithfully passed on to the next generation. It also allows for error correction mechanisms to repair any mistakes that may occur during replication.