How do DNA replication take place? Why do variations occur during DNA replication?
Answers
Answer:
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Explanation:
Imagine DNA to be two strings that are twisted together. In order to separate them, particular enzymes should be used. Firstly, helicase unwinds and unzips the helix at place called replication fork. Moreover, gyrase enzyme helps to relief the strain. Now we have two single strands (as if we had single strings) ready to be complementary paired. Recall that in DNA replication adenine pairs with thymine via triple hydrogen bonds and cytosine pairs with guanine via double hydrogen bonds. Interesting is that adding nucleotides (building blocks of DNA) occurs differently on both strands. RNA primase is used to attach RNA primers. Then polymerase III is an enzyme responsible for single nucleotides attachment. One strand- leading one has nucleotides attached continuously while the other- lagging strand has Okazaki fragments- segments of newly added nucleotides in a disocntinuous way. After nucleotides addition DNA polymerase I replaces RNA primers with DNA. Eventually, ligase joins Okazaki fragments together- genetic material is replicated, ready to enter mitosis and divide.
Variations During DNA replications arise due to mutation that is change in DNA sequence. As no biological reaction is perfect changes in DNA mean that genes are altered which contain certain different proteins responsible for development of body organs.
Due to inaccuracy in DNA replication variations arise.