http://www.ebsi.co.kr/ebs/lms/lmsx/retrieveSbjtDtl.ebs?sbjtId=S20180001029 17강 유전 물질(2) ================================================================================ Suppose following DNA ================================================================================ Cell division Interphase G1 (Gap1) S (synthesis phase) G2 (Gap2) M phase (Mitotic phase) Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis books.google.co.kr/books?id=_fywAwAAQBAJ&printsec=frontcover&hl=ko#v=onepage&q&f=false ================================================================================ DNA replication during cell division, specifically S in Interphase - anabolism: create polymer substance from small molecules - ATP energy is needed ================================================================================ DNA replication way semiconservative replication which is proved by Meselson and Stahl's experiment ================================================================================ * See 2 template strands * Direction of 2 template strands 5' ----- 3' 3' ----- 5' * Decouple the hydrogen bond by helicase * Direction of decoupling * Now, you have 2 separated template strands ================================================================================ * DNA polymerase adds "corresponding base" to the base on the template strands * Red: template strand * Blue: newly added strand ================================================================================ Mechanism of adding new strand Existing nucleotide New nucleotide which has 3 Ps This is called dNTP (deoxyribo-Nucleotide-Tri-Phospate) 2Ps are detached, and P and -OH have "covalent bond" * Point: P is coupled only to -OH at C3 DNA polymerase can't replicate DNA without the prerequisite The prerequisite is the small piece which supplies "-OH at C3" The prerequisite is the RNA piece than DNA piece The prerequisite is actually called "RNA primer" which is synthesized by "primase" Then, DNA polymerase adds new nucleotides https://youtu.be/TNKWgcFPHqw?t=69 * New nucleotide is added at "-OH at C3" What does it mean? New replicated strand is added in the direction of 5' $$$\rightarrow$$$ 3' * See blue strand. 5' is located in the first position ================================================================================ * DNA replication in this strand (leading strand) is fast because replication direction is well fit * DNA replication in this strand (lagging strand) is slow because direction of replication is not fit * Replicate small piece in the direction of 5' \rightarrow 3' * Replicate small piece in the direction of 5' \rightarrow 3' * All replicated pieces are called Okazaki fragment Okazaki fragment is connected by DNA ligase ================================================================================ After DNA replication, RNA primer is removed Then, the place where RNA primer is removed becomes single strand which is unstable So, single strand is decomposed, resulting in a bit shorter DNA ================================================================================ Generally, after 10 replications, cell becomes death If people can protect the end (telomere) of DNA, lifespan becomes infinity ================================================================================ Cancer cell replicates continuously The end of cancer cell is not decmposed So, it will be good if people can apply the telomere-characteristic of cancer cell to normal cell, to increase lifespan ================================================================================