Are there genes and proteins responsible for DNA replication?

Question

Are these the same for all cells and life forms that divide?

Answer 1

The mechanisms of DNA replication are mostly conserved throughout the phylogenetic tree. Just think that what we know today about the mechanisms of replication, we have learnt from the SV40 virus and from the yeast Saccharomyces cerevisiae.

The replication machinery is composed of protein complexes that bind to and recognise particular portion of the DNA molecules to be replicated, called replication origins. The first group of proteins to bind an origin is called ORC (origin recongnition complex), a complex with ATPase activity. The ORC complex interacts with two partners, called cdc6 and cdt1, which together with the ORC complex activate the MCM helicases to load onto the DNA. At this stage, normally happening in early G1 or late telophase, the DNA is said "licensed" for replication. MCM helicases have the role of unwinding the DNA double helix and allow the binding of the polymerases. Before this happens, other partners have to bind to the replication complexes, mostly kinases (enzymes in charge of protein phosphorylation), which will activate the MCM complex, as well as other associated proteins (cdc45, RPA, MCM10, cut5, etc..) which travel with the fork of replication. After the kinases will have performed their job, the polymerase enzymes can load onto the replication fork and begin replication in a bi-directional way. Other proteins, such as the RF complex (replication factor complex) and the ring protein PCNA make sure that the polymerase and DNA interact tightly. Replication proceeds from the 5' end to the 3' end of each strand, and the portions left "empty" are filled in with ligases and other complicated protein complexes.

This is what happens in eukaryotes. Between mammals and yeast, the major difference is that yeast replication origins present conserved sequences - called ARS (autonomous replication sequences) (sorry!), whereas in mammals such sequences have not been identified yet. Other differences are represented by the mechanisms of regulation of DNA replication, mainly which kinases are involved, as mammals cells have many redundant kinases, whereas yeast only one or two.

I could go on, but it is a very complicated field. Hope it helped a bit!

Hei, who gave a thumb down to Pieran? He was not wrong - just what he/she describes happens to keep replication going, whereas what I write here are the steps that lead to DNA polymerase binding to the origin and starting DNA synthesis

Answer 2

Yes, and no.
Yes, there are a large number of proteins that are used in the process of DNA replication. In bacteria, at a minimum, there are six that play key roles

Polymerase is responsible for initiation of the unwinding of the DNA. The tension holding the helix in its coiled and supercoiled structure can be broken by nicking a single strand of DNA. Try this with string. Twist two strings together, holding both the top and the bottom. If you cut only one of the two strings, the tension of the twisting is released and the strings untwist.

Helicase accomplishes unwinding of the original double strand, once supercoiling has been eliminated by the topoisomerase. The two strands very much want to bind together because of their hydrogen bonding affinity for each other, so the helicase activity requires energy (in the form of ATP ) to break the strands apart.

DNA polymerase proceeds along a single-stranded molecule of DNA, recruiting free dNTP's (deoxy-nucleotide-triphosphates) to hydrogen bond with their appropriate complementary dNTP on the single strand (A with T and G with C), and to form a covalent phosphodiester bond with the previous nucleotide of the same strand. The energy stored in the triphosphate is used to covalently bind each new nucleotide to the growing second strand. There are different forms of DNA polymerase , but it is DNA polymerase III that is responsible for the processive synthesis of new DNA strands. DNA polymerase cannot start synthesizing de novo on a bare single strand. It needs a primer with a 3'OH group onto which it can attach a dNTP. DNA polymerase is actually an aggregate of several different protein subunits, so it is often called a holoenzyme. The holoenzyme also has proofreading activities, so that it can make sure that it inserted the right base, and nuclease (excision of nucleotides) activities so that it can cut away any mistakes it might have made.

Primase is actually part of an aggregate of proteins called the primeosome. This enzyme attaches a small RNA primer to the single-stranded DNA to act as a substitute 3'OH for DNA polymerase to begin synthesizing from. This RNA primer is eventually removed by RNase H and the gap is filled in by DNA polymerase I.

Ligase can catalyze the formation of a phosphodiester bond given an unattached but adjacent 3'OH and 5'phosphate. This can fill in the unattached gap left when the RNA primer is removed and filled in. The DNA polymerase can organize the bond on the 5' end of the primer, but ligase is needed to make the bond on the 3' end.

Single-stranded binding proteins are important to maintain the stability of the replication fork. Single-stranded DNA is very labile, or unstable, so these proteins bind to it while it remains single straded and keep it from being degraded.

Each of these is coded for by a specific gene.

However, DNA replication uses many different proteins in other organsims, such as viruses, eukyotes and organelles
http://web.indstate.edu/thcme/mwking/dna.html

Answer 3

yes
DNA replication begins with an enzyme,enzymes contain proteins which break the hydrogen bonds between bases that hold the two strands together, thus unzipping the DNA. As the DNA continue to unzip, nucleotides are attached to their bases by hydrogen bonding. More enzymes bond these nucleotide into a chain until the entire molecule has been unzip and replicated. When all the DNA in the chromosomes have been copied by the cell, ther are two copies of the organism's genetic information.

Answer 4

yes....the prime function of a gene is to make its copies to be transmitted to the daughter cells...
the copying of DNA to make more DNA is known as DNA replication...
the enzyme Helicase is responsible for the unwinding the double helix..
it unzips the two strands...
An enzyme Topoisomerase reduces the coiling tension generated....
DNA polymerase III is the most important DNA synthesizing enzyme...
It along with other DNA polymerases(I and II) has the capability to elongate an existing DNA strand...

Answer 5

yes there r some genes responlsible

Answer 6

yes.

http://en.wikipedia.org/wiki/Dna_replication