44
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How do proteins 'know' where to go?
Even though this animation is very well-known and the narrator says it is "... an accurate representation of the actual DNA replication machine ...", be very careful of its visual appeal. It ...
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Are all Y-chromosomes the same?
Actually, no. There are also recombination prone regions of the Y chromosome that recombine and exchange material with X chromosomes, and these are called pseudoautosomal regions (PARs).
Y ...
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11
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How do proteins 'know' where to go?
This answer is specific to the "two-legged" proteins from the end of the video (motor proteins).
The animation shows identical proteins moving in perfect lockstep, but really there is wide ...
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Does gene orientation relative to origin of replication matter on small plasmids?
I like this question, and I had a similar thought when reading that "Forward or Reverse Strand" post. I've since found a 2005 publication by Mirkin and Mirkin1, which investigates the ...
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9
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How do proteins 'know' where to go?
There have been some suggestions that biological molecules may 'know where to go'.
Barry Honig's group at Columbia analyzed the electrical charge arrangements in protein and proposed that by placing ...
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7
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DNA & mRNA During Transcription
Transcription occurs in a special structure known as transcription bubble. Inside the bubble are present the mRNA, template DNA being transcribed and the RNA Polymerase. Upstream of bubble is the DNA ...
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7
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Do mitochondria contain the genes to specify themselves?
The answer is a bit more complicated than that. Mitochondria contain their own genome called mitochondrial DNA (mtDNA), encoding 13 proteins that are part of respiratory complexes I, III, IV, and V, ...
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7
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Thermodynamically, how did the first cell arise?
The first amino acids
For how life arose from no life, the Miller-Urey Experiment demonstrates how in primordial Earth conditions, a spark in the atmosphere (analogous to lightning) could have ...
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6
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Can mitochondria become cancerous?
Interesting question.
As a prelude, I should probably mention that single celled organisms cannot get cancer as we understand and define it. Mitochondria are not, of course, single celled organisms, ...
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Why is DNA replication so much faster in prokaryotes than eukaryotes?
The difference in DNA replication rate between prokaryotes and eukaryotes is still under current research, but the basics are understood. It is very much a matter of complexity, as eukaryotes are more ...
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Two 20 million yr old fossils of Hummingbirds found "The amazing thing about the fossil is that it's essentially a modern hummingbird
Hummingbirds were not created, they evolved.
Ancestors of a modern species need not be that morphologically different from their progeny, even over a time span of millions of years. And organism will ...
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Why doesn't telomerase activity cause DNA to get longer each time a cell undergoes DNA replication?
I will assume that you are referring to humans, though much of the research to elucidate telomerase function was performed in yeast.
The first reason is that only a small subset of somatic cells ...
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DNA replication: How many DNA polymerase molecules work in parallel?
In the (beautifully rendered) video you linked to, the green molecules are DNA polymerases. So you can already see that there are more than two DNA polymerases at work!
At each replication fork, ...
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Chemistry of phosphodiester bond formation by DNA polymerase
I found this paper, which goes very deep into the molecular details of the individual steps of this reaction and also discusses how this is coupled to nucleotide selectivity.
The 'basic' details ...
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Typical DNA replication times
A mammalian cell takes about 8 hours to replicate all of its DNA in its S phase; a yeast cell would take about 40 minutes.
Some other information that you seem to not have quite the right information ...
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Can DNA replicate without polymerase?
Nope. Not happening.
The high temperature (90 °C) needed to separate a DNA strand also makes an association of free floating bases to a template strand much too unstable.
Even if the bases associated ...
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4
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Role of dam methylase in bacteria
The dam methylase has three different functions:
Correction replication errors, since the new DNA molecule
is only hemimethylated (the old strand is methylated, the newly
synthesized is not). Since ...
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4
votes
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When does histone synthesis occur in relation to DNA replication?
Yes, they have to. But that is just half of the story.
The (canonical) histones which are used in DNA replication are synthesized at the beginning of the S phase, and subsequently transported into ...
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4
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Typical DNA replication times
I think your view of DNA replication is a little off-target in relation to strand separation (which produces what you call “single helix structure”). The strands of the DNA are separated continually ...
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4
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Why does the structure of RNA change?
Summary
Most nucleic acid species have specific structures (or a limited number of alternative structures) which may involve a greater or lesser amount of double helix through complementary base ...
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Time required for DNA replication in E. coli
Remember that E. coli has a single circular chromosome, and that chromosome is replicated bidirectionally. Hence, your calculated value (90 minutes) is exactly twice that of the correct answer.
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Why do eubacterial DNA Ligases use NAD whereas eukaryotic and archaeal DNA Ligases use ATP?
This difference is certainly intriguing, but, like many other general ‘why?’ questions, can be approached on different levels.
Because they evolved differently.
is one answer, and not a trivial one ...
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3
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How do point mutations arise from mistakes in DNA replication?
Source of your misunderstanding
Your misunderstanding is very comprehensible as the figure is misleading.
The figure only shows a single event of replication. What you see as a second replication ...
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The Semi-Conservative Model of DNA Replication: Question
I believe the reason you are having trouble understanding the concept is due to a poor usage of colors in the diagram. Don't focus on the colors, but on the concept. It's the same for both replication ...
3
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Why isn't the DNA in bacteria always split up and replicating?
Bacterial DNA replication is initiated at the oriC by DnaA in E. coli. Think about ways in which DnaA binding or activity can be regulated in a way that inhibits or permits DNA replication. In ...
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When does histone synthesis occur in relation to DNA replication?
In Molecular Biology of the Cell (Chapter 4), it is written that
The major histones are synthesized primarily during the S phase of the cell cycle and assembled into nucleosomes on the daughter DNA ...
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How is a portion of DNA selected and unwound from nucleosome?
This answer will be a very broad overview and is based largely on information from the textbook "Molecular Biology of the Gene" by Watson et al. (which I highly recommend).
Nucleosomes are dynamic ...
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3
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Don't understand how multiple replication bubbles work
You mistake replication direction with polymerase synthesis direction. Indeed, the polymerase synthesizes new strands 5' -> 3' but if the replication of each strand was continuous, there would be no ...
3
votes
After the primer is removed from the leading strand, how does DNA polymerase I add dNTPs without a 3'-OH?
The leading strand post-initiation
First consider the DNA replication fork after initiation has occurred.
The 3′-OH primer on the leading strand is the 3′-end of the strand of DNA being synthesized in ...
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Why does inbreeding cause genetic defects, but cell division in one's own body does not?
I suspect your problem is grasping what is a deleterious recessive allele. Wikipedia and textbooks explain it much better but I will try to illustrate with respect to your question.
I have to merge ...
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