Questions tagged [dna-replication]

The biosynthetic process by which copies of a DNA molecule are made.

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28
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4answers
255k views

Why is DNA replication performed in the 5' to 3' direction?

DNA replication goes in the 5' to 3' direction because DNA polymerase acts on the 3'-OH of the existing strand for adding free nucleotides. Is there any biochemical reason why all organisms evolved to ...
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2answers
3k views

Why and how is DNA synthesis so much faster then RNA synthesis in bacteria?

DNA synthesis in E. coli is 20x faster than RNA synthesis at 1000nt/s vs 50nt/s. (Mirkin'05) I find that perplexing since DNA polymerization has better proofreading than the RNA variety, which ...
12
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2answers
253 views

Are there viruses that affect cells across different species?

I'm not a professional in biology nor a student, but I'm curious about this. To be more specific: why doesn't a plant virus affect animal cells? I suspect that different kinds of cells have different ...
11
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2answers
972 views

Why, specifically, does each generation, on average, improve upon the design of the species rather than degrade it?

In every non-life example I can envision, a copy of a copy is always a degraded or less pure version of the original unless some outside influence acts to correct the copy back toward the ideal ...
11
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1answer
2k views

Are all Y-chromosomes the same?

Since the Y-chromosome can only pass from male to male child, it would seem to pass intact. Thus, a boy's Y-chromosomes would, I guess, be the same as his father's. Going backwards, would not all men ...
11
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1answer
253 views

Can mitochondria become cancerous?

Given that mitochondria have their own DNA and can replicate independently, can they ever become cancerous? For example, could a mutation in their DNA cause them to rapidly replicate, ultimately ...
11
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1answer
7k views

Difference in length of Okazaki fragments

The length of Okazaki fragments in the lagging strand is about 100-200 nucleotides in eukaryotes and about 1000-2000 nucleotides in prokaryotes. What (molecular mechanism, enzyme type ) determines ...
9
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1answer
733 views

When do plasmids replicate relative to its host cell cycle?

For plasmids is so much shorter than their host cell's genome (about 1/1000 in my case), it will take only 1/1000 time for it to replicate. With respect to cell cycle, when will that replication ...
9
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2answers
1k views

When does histone synthesis occur in relation to DNA replication?

Do histones have to be synthesized before DNA is replicated to allow the DNA to coil around histones?
9
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2answers
1k views

Which bacteria have the highest mutation rate?

From my reading on M. tuberculosis, I know that this organism has a pretty high mutation rate due to uncorrected sloppy replication, which leads to a high rate of development of spontaneous resistance ...
8
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2answers
2k views

How can E. coli proliferate so rapidly?

The E. coli has a genome with approximately 5×106 bp. The main DNA polymerase involved in its chromosome duplication (DNA pol III , the one with highest processivity) can polymerize ~103 nucleotides ...
7
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1answer
492 views

DNA & mRNA During Transcription

Just a simple, quick question: how are the mRNA and the template strand of the DNA structured during transcription? I've seen models and videos of them when they're both flat/straight (is that just ...
7
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1answer
463 views

Why doesn't telomerase activity cause DNA to get longer each time a cell undergoes DNA replication?

Telomerase extends the ends of the lagging strands in order for all of DNA to be be copied. Doesn't this also mean that DNA gets progressively longer each time it undergoes replication? Why is this ...
7
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3answers
383 views

How is a portion of DNA selected and unwound from nucleosome?

If I understand this correctly during interphase most of the DNA strand is tightly wound around histones in the form of nucleosomes, to conserve space in the nucleus. Yet RNA polymerase in order to ...
6
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1answer
222 views

What regulates the timing of the motion of molecular machines during DNA Replication?

This question is about this video I found on Youtube. I just want to know what is the mechanism which regulates the timing of motion of the parts of these molecular machines. I know that those big ...
6
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1answer
674 views

How do point mutations arise from mistakes in DNA replication?

Hi! I'm trying to make sense of this illustration (from the textbook Biological Science by Scott Freeman). The general question is: How do point mutations arise from mistakes in DNA replication? If ...
6
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1answer
64 views

How does bonding between non-complementary bases occur?

My teacher told me that when DNA polymerase makes an error (roughly every 10 million nucleotides?) that if, for example, it matches an A with a G that the error remains and is the main cause of point ...
5
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2answers
129 views

Do somatic cells alter their own nucleotide sequence?

I seem to remember reading that embryonic cells will frequently replicate the section of their genome containing rDNA by splicing in duplicate genes. The cells use this to produce ribosomes at a rate ...
5
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1answer
837 views

DNA content doubling in interphase

Why does the DNA content of a cell get doubled in interphase? Why doesn't it become tripled or quadrupled? What's stopping it from doing so?
5
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1answer
245 views

How do mutations actually occur?

DNA replication seems so mechanical- the DNA polymerase just running along the template strand. I just don't understand how mutations can arise. When it comes to substitutions, I get that a wrong ...
4
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1answer
7k views

Does DNA polymerase always go the same direction?

I read that mutations are more likely to occur on "the strand that DNA polymerase replicates discontinuously". Does DNA polymerase always replicate the same strand discontinuously and, if so, how/why?
4
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1answer
372 views

Do telomeres appear at just one end of the chromosome?

I have just studied DNA Replication for my Biology Class and I have this question that leaves me stuck, though I have tried to figure it out myself. During telomere replication, I am aware Telomerase ...
4
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0answers
115 views

What would the resulting karyotype be if someone with Klinefelter syndrome fertilized an “empty” egg?

Endoreduplication: is a form of nuclear polyploidization that results in multiple, uniform copies of chromosomes. This process is common in plants and animals, especially in tissues with high ...
3
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2answers
805 views

How are DNA segments selected in PCR?

I understand that in PCR we're able to amplify only selected portions of the DNA... however despite reading it from multiple sources, I cannot figure out how this selection actually takes place. I ...
3
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2answers
298 views

Chemistry of phosphodiester bond formation by DNA polymerase

As I'm teaching General Biology to my college students, I realized that I don't fully understand how a 3-P nucleotide like ATP is broken down to be incorporated into DNA during replication. How does ...
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1answer
1k views

Can replication occur if DNA is methylated?

Can a methylated strand of DNA be replicated without removing methylation? Does it make any difference if the strand is methylated or not (during replication)?
3
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2answers
8k views

What does this equation about DNA replication mean?

Could someone help me understand this equation please? I found it in a paper which said that it was DNA replication, but why? $\ce{dNTP + dNMP_{n} -> dNMP_{n +1} + PPi}$ I found that dNTP means ...
3
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1answer
5k views

ATP required for cell processes [closed]

I haven't been able to find anything that tells me how much ATP is needed for DNA replication, transcription, and translation in humans, just papers that mention ATP used in those processes. I need ...
3
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2answers
844 views

DNA polymerase I exonuclease activity

Does DNA polymerase I in bacteria use forward or reverse exonuclease activity to remove RNA primers? One of my books says it uses 5' to 3', but another says it uses 3' to 5' exonuclease activity. ...
3
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1answer
254 views

Specific numbers of nucleotides in Okazaki fragments

Okazaki fragments are formed during replication of the lagging DNA strand. What determines the length of these fragments?
3
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1answer
29k views

Does DNA replication in 5' to 3' (leading strand) need RNA primase?

https://www.youtube.com/watch?v=27TxKoFU2Nw In the above video it shows that during DNA replication, the lagging strand require RNA primase to add 3' -OH group for further addition of nucleotides. ...
3
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1answer
3k views

Telomere shortening during replication

It is widely know that each cell cycle during DNA replication some fraction of the telomeres is lost, and this phenomenon is called the end replication problem. Well this is due to the fact that the ...
3
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1answer
5k views

What happens when cells in your body run out of telomeres?

In my biology book I read about an experiment where the genes encoding telomerase were 'knocked out', but they could still live a normal life and no adverse effects were noticed until the 6th ...
3
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1answer
818 views

What is a DNA clamp exactly?

I used to think that a DNA clamp is a protein. But today I noticed it doesn't appear in this picture. Then I went to it's Wikipedia page, where it was written: A DNA clamp, also known as a sliding ...
3
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1answer
764 views

Reason behind formation of positive supercoils during DNA replication/ transcription

When a twist is unwound without cutting the DNA strands or is removed by cutting the strand(s) and resealing, negative supercoils are introduced in the DNA. From Cell and Molecular Biology -Karp But ...
3
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1answer
630 views

Why do some bacteria have an asymmetric replication?

Our teacher said that Bacillus subtilis has an asymmetrical replication fork. I know that this happens only in some strain of the bacteria . She asked us to find an explication for this mechanism , ...
3
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1answer
51 views

Are bacterial RNA polymerases distributed evenly throughout the cell or localized?

Bacterial cells aren't internally compartmentalized with membranes (like eukaryotes). This naturally leads to an image of a homogeneous interior, but bacterial cytoplasm isn't homogeneous. Case in ...
3
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1answer
320 views

What is the purpose of two cell divisions in meiosis?

At the moment, my thoughts are that the two cell divisions are necessary for recombination to occur, although I am not sure. I cannot really see why technically, the chromosome from each parent cannot ...
3
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2answers
136 views

From an information perspective, are both strands of DNA necessary?

I am learning about the genetic code, replication, and transcription, and I have a question about whether or not both strands of DNA are really "necessary". In replication, at a high level, we are ...
3
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1answer
660 views

Does DNA polymerase I require a $3^\prime$ end?

DNA polymerase III adds nucleotides in the $5^\prime \rightarrow 3^\prime$ direction because it can only add nucleotides to the $3^\prime$ end of the previous nucleotide. This is why it requires a ...
3
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0answers
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Can a dividing cell that skipped DNA replication become cancerous?

Let's assume that a cell fails to replicate its DNA during the S Phase of the cell cycle. Let's also assume that the appropriate CDKs are inactive (perhaps due to mutation or lack of cyclin proteins ...
3
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0answers
66 views

DNA replication precision

This will sound as a super stupid question, but I just read in the Molecular biology of the gene book (7th edition, Watson, Baker, Bell and al.) that one mistake occurs in 10 million nucleotides added ...
3
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2answers
92 views

Molecular animations of, say, protein synthesis, are simplified, but how exactly?

In several animations of biological processes (eg protein synthesis (go to frame 1.20mins), DNA replication, etc), molecules such as amino acids are shown heading straight to the replicating protein ...
2
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2answers
239 views

Typical DNA replication times

Just out of curiosity (I am completely strange to biology), as I have been unable to find this info on the internet: How long does the whole DNA replication process take? (say, the replication of a ...
2
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1answer
124 views

Do mitochondria contain the genes to specify themselves?

My book says : "Mitochondria contain their own genetic material so when a cell divides, the mitochondria replicate themselves under the control of the nucleus." The book means that the mitochondria ...
2
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1answer
2k views

DNA replication: How many DNA polymerase molecules work in parallel?

Background research I am aware that DNA polymerase works in pairs, at least. This is to process both opposite stands of a given chromosome. The 3'-to-5' "leading strand", and 5'-to-3' "lagging strand"...
2
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1answer
438 views

Role of dam methylase in bacteria

In bacteria, an enzyme called dam methylase (Deoxyadenosine methylase) methylates adenines (A) in the sequence GATC in the new strand formed after replication. What role does this methylation play? ...
2
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1answer
117 views

Why isn't the DNA in bacteria always split up and replicating?

Isn't helicase always free floating in bacterial cells, and the DNA without a nuclear membrane and uncoiled and freefloating and so why doesn't the helicase keep breaking the double helix of DNA? Also,...
2
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2answers
547 views

Bacteria Replication

I learned this at a lecture, but somehow I have trouble in understanding this. It is said that the bacteria such as E.coli need 20 minutes to divide, but its chromosome require 40 minutes to multiply. ...
2
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1answer
2k views

Does DNA helicase or topoisomerase actually “unwind” DNA?

I am reading through my textbook (Genetics, Brooker 4th edition) and the summary it gives seems imprecise for the functionality of helicase and topoisomerase. The following is an exerpt: ...