DNA and Replication

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DNA and Replication

You pose an interesting question – There are different types of Human

DNA – which there are various classifications, Chromosomal DNA and

Mitochondrial DNA. There is also the DNA present from normal flora

microorganisms such as bacteria, viruses, mites, etc. Some of this

microorganism DNA may be significant, such as E. coli DNA in the gut

or Staphylococcus DNA on the skin. You even have DNA present from

viruses of bacteria such as phage DNA. Some human viruses may be

present in blood cells such as EBV, CMV in nerve cells like herpes

simplex 1, in skin cell like HPV (human papilloma virus) or integrated

into the Human Chromosomal DNA such as various retroviruses, like

human foamy virus, HTLV or HIV

Within Chromosomal DNA there is DNA that codes for genes- exons (mRNA

coding) and non coding regions called introns. There are regions of

DNA within the introns that are called endogenous retroviruses – these

regions have great similarity to retroviruses and may have disease

implications.

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An Okazaki fragment is a relatively short fragment of DNA that is

created by primase and Pol III along the lagging strand (see DNA

replication). They are later removed by RNAse H, and the last

ribonucleotide is removed by and synthesized by Pol I. The nick, or a

broken phosphodiester bond remaining between the fragments is linked

together by DNA ligase

The replication fork is a structure which forms when DNA is ready to

replicate itself. It is created by topoisomerase, which breaks the

hydrogen bonds holding the two DNA strands together. The resulting

structure has two branching "prongs", each one made up of a single

strand of DNA. DNA polymerase then goes to work on creating new

partners for the two strands by adding nucleotides.

A primer is a nucleic acid strand (or related molecule) that serves as

a starting point for DNA replication

Oka-what? Another Look at Okazaki Fragments.

As you have already learned, the two strands of DNA are antiparallel.

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