DNA replication
DNA replication is the process of copying a double-stranded DNA molecule. Both strands serve as templates for the reproduction of the opposite strand. The process is sometimes called "semi-conservative replication" because the new DNA from the original strand contains half of the original and half of the newly synthesized DNA.
![](http://up.wiki.x.io/wikipedia/commons/thumb/7/70/DNA_replication_split.svg/150px-DNA_replication_split.svg.png)
This process occurs in all life forms with DNA.[1] There are some differences in the control of DNA replication in prokaryotic and eukaryotic organisms.
In a cell, DNA replication begins at specific places in the genome, called origins.[2] As the DNA unwinds and as DNA helicase rips apart the double helix structure of DNA,[3] the synthesis of new strands forms at a replication fork.[4] In addition to DNA polymerase,[5] other enzymes at the fork help to start and continue the DNA synthesis.
DNA polymerase
changeDNA polymerases are a family of enzymes that carry out all forms of DNA replication.[6] However, a DNA polymerase can only extend an existing DNA strand paired with a template strand; it cannot begin the synthesis of a new strand. To begin synthesis, a short fragment of DNA or RNA, called a 'primer', is created and paired with the template DNA strand.
In general, DNA polymerases are extremely accurate, making less than one mistake for every 107 (10 million) nucleotides added.[7] Even so, some DNA polymerases also have 'proofreading' ability: they can remove nucleotides from the end of a strand in order to correct mismatched bases.
DNA repair
changeDNA in cells is constantly being damaged.[8] The nucleus of cells contains a number of repair mechanisms which fix almost all of this damage. "A large set of DNA repair enzymes continuously scan the DNA and repair any damaged nucleotides".[9]
References
change- ↑ Most viruses use RNA instead.
- ↑ Berg J.M.; et al. (2002). Biochemistry. W.H. Freeman. ISBN 0-7167-3051-0.Chapter 27, Section 4: DNA Replication of both strands proceeds rapidly from specific start sites
- ↑ Encyclopaedia Britannica (2023-03-20). "DNA replication". britannica.com. Retrieved 20 March 2023.
- ↑ Mazouzi, Abdelghani; Velimezi, Georgia; Loizou, Joanna I. (2014-11-15). "DNA replication stress: Causes, resolution and disease". Experimental Cell Research. DNA DAMAGE AND REPAIR. 329 (1): 85–93. doi:10.1016/j.yexcr.2014.09.030. ISSN 0014-4827. PMID 25281304.
- ↑ The enzyme which synthesizes new DNA by adding nucleotides matched to the template strand.
- ↑ Berg J.M.; et al. (2002). Biochemistry. W.H. Freeman. ISBN 0-7167-3051-0. Chapter 27, Section 2: DNA Polymerases require a template and a primer
- ↑ McCulloch S.D. & Kunkel T.A (2008). "The fidelity of DNA synthesis by eukaryotic replicative and translesion synthesis polymerases". Cell Research. 18 (1): 148–61. doi:10.1038/cr.2008.4. PMC 3639319. PMID 18166979.
- ↑ Causes include reactive molecules, chemicals and radiation from the environment, and damage caused by heat.
- ↑ Alberts B et al 2002. Molecular biology of the cell. 4th ed, Garland. p275. ISBN 0-8153-3218-1
Other websites
change- DNA Workshop
- WEHI-TV - DNA Replication video Archived 2007-10-12 at the Wayback Machine- Detailed DNA replication animation from different angles with description below.
- Basic Polymerase Chain Reaction Protocol Archived 2007-10-13 at the Wayback Machine
- Animated Biology Archived 2007-10-27 at the Wayback Machine
- DNA makes DNA Archived 2004-09-15 at the Wayback Machine (Flash Animation)
- DNA replication info page by George Kakaris MSc.
- Reference website on eukaryotic DNA replication
- [“DNA Replication.” Genome.gov, https://www.genome.gov/genetics-glossary/DNA-Replication.]
- [“Structure and Composition of DNA.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/heredity-genetics/Structure-and-composition-of-DNA#ref944097.]