Leading Strand: Priming, Placement, and Primers

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In summary, the leading strand moves in the right direction at a rate of 500-5000 base pairs per minute in eukaryotes and 1,000,000 base pairs per minute in bacteria. The source of the movement is debated, with some evidence suggesting a central non-moving replisome in bacteria. The placement of RNA primers on the leading strand appears to be random, but they are synthesized at regular intervals. In eukaryotes, there will be a large number of primers on the leading strand compared to the lagging strand, with approximately 1 primer per 200 base pairs. It is possible to have double-stranded RNA, but the body has mechanisms, such as TLR-3, to
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student007
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Question: How does the leading strand work? (I know that it moves in the right direction...i.e. relatively fast) Where is the RNA primer placed on it (i.e. is it just an arbitrary point)? On eukaryotic DNA, about how many total primers will there be on the leading strand relative to the lagging strand?

(This is not a homework question. I have a quiz tomorrow, and i approached these issues while studying)
 
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student007 said:
Question: How does the leading strand work? (I know that it moves in the right direction...i.e. relatively fast)

the rate for eukaryotes DNA polymerase is about 500 to 5000 base pairs per minute and for bacteria it can reach 1,000,000 base pairs per minute.

The source of the movement is debate. It is usually accepted that polymerase and other enzymes, which as a group is called the replisome, are moving along the DNA strand. However, there is evidence in bacteria that there is a central non moving replisome and that the DNA is pushed through the replisome.

student007 said:
Where is the RNA primer placed on it (i.e. is it just an arbitrary point)?

It appears to be random but primers are synthesised at a fairly regular interval.

student007 said:
On eukaryotic DNA, about how many total primers will there be on the leading strand relative to the lagging strand?

there will be alot. In E. coli, there 1 primer per 1000 base pairs. In eukaryotes, the Okazaki fragments are shorter so the frequency would be lower,it is around 1 every 200 base pair. Just do to math, the human genome has 6 billion base pair, Encephalitozoon cuniculi has the smallest genome with 2,9 million base pair and yeast has 12,5 million base pair. Some amphibiands and some plants can have over 100 billion base pair genome.
 
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Thanx...one other thing...just wondering...is it EVER possible to have a double-stranded RNA molecule
 
  • #4
Only some virusses have dsRNA, the human body has Toll-like receptors that recognize dsRNA (TLR-3) and induces the innate immune response to break down cells expressing it.
 
  • #5
Yes, it is possible to have double-stranded (ds) RNA; however, the dsRNA are quickly degraded in the cell and dsRNA can be used to regulate gene expression. Some viruses have dsRNA genome. It has been sugested that the machinery that degraded dsRNA has evolved to protect the cell against dsRNA viruses.
 
  • #6
Interestingly you can knock-down genes in mammals by injecting dsRNA: the normal RNA for that transcript will be down-regulated.
 

1. What is the leading strand in DNA replication?

The leading strand is the template strand of DNA that is replicated continuously in the 5' to 3' direction during DNA replication. It is called the leading strand because the DNA polymerase enzyme can add nucleotides in the same direction as the replication fork is moving.

2. What is priming in DNA replication?

Priming is the process of adding a short RNA primer to the template strand of DNA before DNA replication can begin. This primer provides a starting point for DNA polymerase to begin adding nucleotides and allows for the formation of a new complementary DNA strand.

3. How is the leading strand primed in DNA replication?

The leading strand is primed by an enzyme called primase, which synthesizes a short RNA primer complementary to the template strand. This primer is then used by DNA polymerase to start adding nucleotides and continue replicating the DNA strand in the 5' to 3' direction.

4. What is the role of placement in DNA replication?

Placement, also known as elongation, is the process of adding nucleotides to the growing DNA strand in the 5' to 3' direction. This is done by DNA polymerase, which reads the template strand and adds complementary nucleotides to form the new DNA strand.

5. What is the importance of primers in DNA replication?

Primers are crucial for DNA replication because they provide a starting point for DNA polymerase to begin adding nucleotides. Without primers, DNA polymerase would not have a template to follow and DNA replication could not occur. Additionally, primers also help to ensure the accuracy and fidelity of DNA replication by providing a checkpoint for the correct placement of nucleotides.

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