20

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 chromosomes can be used similarly to mitochondrial DNA to build up profiles of ancestry, but the sequences used for this purpose lie outside PARs, in the non-recombining ...


7

Note: In your PCR program you always set extension time. Case: Product length = 500bp PCR extension time = 50sec Assuming that polymerase adds 1000 nt/min Cycle 1: Strand that binds FP: extends ~800nt to the right (as per the polymerization rate): 300 bp ahead of RP complementary site. This product is lets say P1 Strand that binds RP: extends ~800nt to ...


7

So in mitosis, the cell has to split itself into two cells; each daughter cell has a functional genome that may again split into more daughter cells. The cell replicates the DNA before dividing, so the error in replicating 3x or 4x is that upon division, the daughter cells will have more DNA than the initial cell, and every generation will have more DNA than ...


7

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, 22 transfer RNAs (tRNAs), and two ribosomal RNAs (rRNAs). The separate tRNAs and rRNAs are necessary because the mitochondrial genome uses a slightly different ...


7

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 already transcribed and downstream is the DNA to be transcribed. There is not enough space in cell to have completely unfolded DNA for transcription, so ...


6

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, they are organelles, but this interesting question involves treating them as if they were autonomous. We'll come back to that later. First, single-celled ...


5

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 fill a niche based on its fitness to survive in the niche. If there are strong selective pressures in the environment to maintain the traits that we see today,...


5

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 express telomerase. Most somatic cells are terminally differentiated and mitotically inactive, so they are not called upon to replicate their DNA and divide. And ...


5

Summary: In bacteria or organisms with only one well defined replication origin and a circular chromosome, yes for a given DNA region the same strand is replicated discontinuously. In high order animals, which replicate chromosomes using several origins of replication (ori), this is less clear as the way ori are recognized is still not fully understood but ...


5

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, there is generally one DNA polymerase working on the leading strand, but on the lagging strand, multiple DNA polymerases may be working at the same time (as ...


5

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 about the reaction (quoted from this section, which also has a nice figure): The polymerization reaction proceeds by a simple nucleophilic attack of the 3'OH ...


5

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 about: The DNA polymerase does not unwind/split the DNA—that is the job of DNA helicase. The DNA polymerase cannot bind to the single-stranded DNA until the ...


4

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 the proof-reading only takes place on the new strand, errors introduced during replication can be corrected. Regulation of replication: The ori of the ...


4

I'm not completely clear when you say "what makes the replication terminate when the polymerase reaches the primer at the other end" since when you perform a PCR you go through three phases. The denaturation, whereby the two DNA strands become single stranded, then the annealing, which is when primers attach to their appropriate matching site (but the ...


4

There are many way in which DNA can be damaged. As already pointed out in the comment by @skymninge, the Wikipedia page on DNA repair, as well as the mutation page detail some of the things that can go wrong. You say: If G goes with C and A goes with T, I don't see how that part can mess up. This, however, would imply that the four bases are completely ...


4

For DNA replication and transcription you need NTPs. In a dsDNA purine content will be same as pyrimidine content. I am considering that all nucleotides are synthesized de novo which would consume more ATP than getting nucleotides from the salvage pathway.                  &...


4

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 the nucleus. Studies have shown that newly synthesized DNA is immediately packed into nucleosomes. Thus, it is necessary that these structures are available prior ...


4

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 as replication occurs and then they are copied quite quickly by DNA polymerase. They are not separated completely and then copied. (And DNA polymerase doesn’t ...


3

The length of Okazaki fragments is not necessarily a tight distribution. The lengths are determined by the spacing between adjacent sites where DNA primase has synthesized a short RNA primer on the lagging strand at an active DNA replication fork. In E. coli, as I recall, this occurs on an average of once per 1000 nt. DNA polymerase holoenzyme then uses ...


3

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 events. Each strand of a double helix is used as a template to make a new complimentary strand, giving rise to two new DNA helices from the original. In each ...


3

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 recently replicated bacterial DNA, the DNA is hemimethylated (parental strand has a methyl group, daughter strand doesn't): An inhibiting protein binds to ...


3

TCT AAC TGA TTA GC T CTA ACT GAT TAG C TC TAA CTG ATT AGC AGA TTG ACT AAT CG <<< this is the ORF A GAT TGA CTA ATC G AG ATT GAC TAA TCG If the sequence comes from the middle of a gene we assume it should encode an open reading frame. For this sequence only 1/6 frames does not include a stop codon (shown above in italics). So in standard format,...


3

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 resulting into two double stranded molecules is NOT an event of replication. It actually represents the two possible outcomes from a 'mismatch repair mechanism'. ...


3

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 helices just behind the replication fork (see Figure 5–32). In contrast, most histone variants are synthesized throughout interphase. They are often inserted ...


3

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 structures. The interactions between DNA and histones are non-specific and dynamic. Regions of DNA can be transiently unwrapped from the nucleosome and thus ...


3

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 such structure as a replication bubble whatsoever. Take a good look at the drawings: The thing is the direction of replication is consistent with the direction ...


2

On the sequence alone, you can answer neither of these questions because: from the sequence alone you don't know anything about the gene or the promoter. the same is true for the orientation and the codons, since you don't know if the code is in frame or not. If one base is cut-off from the original sequence, your codons shift, and don't show the original ...


2

There's not much difference between them. The same enzyme and condition can be used whether the template is circular or linear. You can amplify plasmids, but PCR intrinsically generates linear DNA fragments even if you use circular DNAs.


2

Mutation of DNA can be caused by an exogenous or endogenous source. Many external factors like irradiation or chemicals induce mutations. Some endogenous mutations arise from oxidative stress, insufficient DNA repair or spontaneous mutations on the molecular level. There are many mechanisms for DNA repair like base excision repair, nucleotide excision ...


2

The replication fork itself is always asymmetric. This is true for all organisms and is due to the fact that DNA polymerases can only add nucleic acids to the 3'-OH end of DNA. This leads to different mechanisms for the replication of the so called leading and lagging strands. You can find more details on wikipedia https://en.wikipedia.org/wiki/...


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