Why is there no helicase in PCR? Need precise answer.?

Posted by Jack on December 12, 2022
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    Hi there! I'm a biochemistry student and have been doing some research on polymerase chain reaction, but have run into an impasse. I was wondering if you could help me out?

    I want to know the exact reason why there is no helicase in PCR.

    As I understand it, the reason there is no helicase in PCR is because you don't need it. Taq polymerase can copy DNA without a helicase, so the enzyme that does this job for you is unnecessary.

    The reason why you need a helicase is to unwind the DNA so that it can be copied. The enzyme unwinds the double helix and uses one strand as a template for building a new strand (the other will remain unchanged). Taq polymerase copies only from single-stranded DNA, which means that if your sample contains both double-stranded and single-stranded DNA, then your reaction won't work properly.

    What is the difference between reverse transcriptase and polymerase chain reaction?

    Reverse Transcriptase is an enzyme that converts RNA into DNA. PCR is a technique in molecular biology used to amplify a single or few copies of a specific DNA fragment from among millions of other DNA fragments present in the sample.

    What enzyme could be added to PCR to introduce targeted mutations?

    You could use a mutagen to introduce mutations into an organism. Mutagens are enzymes that introduce point mutations and frameshifts during replication.

    PCR is a tool used to detect specific DNA sequences in DNA samples, so it would be important for you to understand what your goal is before you add an enzyme into the reaction. For example, if your goal was to make sure that your PCR product has been modified by the mutagen and has introduced a specific mutation at one of its sites, then perhaps you'd want to choose an enzyme that creates specific mutations at locations where it recognizes certain sequences directly rather than randomly throughout the genome as happens with most mutagens (like ethidium bromide).

    Why do we have to denature DNA when starting a PCR instead of allowing Taq Polymerase to bind directly?

    PCR is a very efficient process for amplifying the desired DNA sequence. However, it's important to note that the Taq Polymerase does not bind directly to double-stranded DNA. Instead, it needs to bind only to single-stranded DNA in order to start copying the template strand.

    The reason for this is because your template DNA sample contains both single-stranded and double-stranded regions of sequences. The double strands of your template are complementary mirror images of each other and can't be copied by the Taq Polymerase because they're already double stranded! This means that one side will have A's while its partner side has T's - these would lead to sticky ends if they were copied together during replication (which can be problematic). Instead, we use heat denaturation (heat up) after annealing primers at 96 degrees Celsius for 10 minutes so that all strands become single stranded again before adding Taq Polymerase...

    What is the role of primers in polymerase chain reaction (PCR)?

    Primers are DNA fragments that are designed to bind to the target DNA, and then be extended by the polymerase enzyme. The term "primer" refers to the fact that they need to bind to a specific part of your intended target before the polymerase can start adding more nucleotides onto the existing strand. Once it binds, it's called an "extension product" (or just extension).

    The most important thing about primers is that you need them for PCR! In order for a polymerase chain reaction (PCR) to work properly, you must create two complementary strands of DNA from whatever source material you have. This means that you're going only copy one strand over again many times; this is called exponential amplification because after one round of replication produces two new copies with each cycle (hence "exponential"), but eventually reaches saturation point when all available free molecular sites have been used up. In order for this whole process not repeat endlessly without producing any new information (which would happen if all four bases were present at every position), we need some way to ensure only one base pair exists in each position during each step along its journey from beginning through completion—and this is where primers come into play!

    Why is it required that the melting temperature of primers should be 58-60 degrees Celsius, and not much higher or lower?

    You have to make sure that the melting temperature of your primers is 58-60 degrees Celsius, and not much higher or lower. Otherwise, the polymerase will not bind to the primer. This is due to the high specificity of Taq DNA polymerase.

    For example, if you use a primer with a melting temperature of 80 degrees Celsius (an extreme case), then your DNA template cannot be amplified because any strand fragments that form during PCR will melt at such high temperatures and reform into single strands instead of double strands when they are melted by heat denaturation after elongation by Taq DNA polymerase in reaction mix under conditions where no primer is present for hybridization.

    Is it possible for a primer in primer extension reaction to bind at multiple sites on a single strand of DNA?

    The primer will bind to the first site it encounters. The enzyme will extend the primer by adding nucleotides to the 3' end. This process continues until all four nucleotides are added and the primer can no longer bind to that specific site on DNA.


    Reverse transcriptase, a class of enzymes, is the enzyme that allows HIV to replicate. It is also used in the process of PCR, which we'll get into later. But there's one thing you should know: none of these enzymes can be called "helicases." There are no helicases in either reverse transcriptase or polymerase chain reaction (PCR).

    The reason why this happens is because reverse transcriptase and polymerase chain reaction (PCR) are two different types of processes that use different kinds of enzymes for their jobs; so it's possible to use RNA polymerases to help make DNA from RNA, or use DNA polymerases with proofreading activity for your PCR reactions—and both will work perfectly well without needing any kind of helicase!


    This is a very interesting question, and one that I'm sure many people have asked themselves. The answer is not quite as complicated as you might think; it's actually pretty straightforward. So let's dive into it!

    Why is there no helicase in PCR? Well, first off, the polymerase chain reaction (PCR) isn't really a helicase-dependent process at all. It relies on an enzyme called Taq polymerase which can be found in nature but has been modified so that it works better with DNA than other similar enzymes do -- meaning that it helps amplify your target sequence more efficiently than they could ever hope to do alone! So there aren't any problems related specifically towards this process losing its ability due to lack of helicases being present in the mix - they aren't needed anyways (or so we thought).

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