When these bases are bound to a sugar 2-deoxyribose for DNA , they form the nucleosides Adenosine, Cytidine, Guanosine or Thymidine respectively:. When the nucleosides are bound to one or more phosphate groups, they become nucleotides. The general structure of a nucleotide is source :. Finally, nucleotides are joined together through their phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings.
This polymer is what we know of as DNA:. So, after this long introduction, the acidity of DNA is caused by the presence of the phosphate groups which are themselves acidic.
You can see this by comparing the structure of DNA to that of Phosphoric acid:. As explained very well here :.
In chemical terms, such a group is called a phosphate diester. The remaining proton is now quite acidic, and is relatively easily lost, thereby giving DNA its acidic character. Indeed, under neutral conditions, DNA is deprotonated at this site, and the oxygen atom bears a negative charge.
Despite the fact that DNA does contain many basic groups, their basic properties are masked somewhat because of the fact that they hydrogen bond with each other to form base pairs. DNA is made of three types of molecules in equal proportions - basic nucleotides, sugar deoxyribose and acidic phosphate groups.
The bases are on the inside of the helix and partly hidden from the outside. Deoxyrybose and phopshates are on the outside, forming a backbone. This language tells the cell's protein-making machinery the precise order in which to link the amino acids to produce a specific protein. This is a major task because there are 20 types of amino acids, which can be placed in many different orders to form a wide variety of proteins. But nearly a century passed from that discovery until researchers unraveled the structure of the DNA molecule and realized its central importance to biology.
For many years, scientists debated which molecule carried life's biological instructions. Most thought that DNA was too simple a molecule to play such a critical role.
Instead, they argued that proteins were more likely to carry out this vital function because of their greater complexity and wider variety of forms. By studying X-ray diffraction patterns and building models, the scientists figured out the double helix structure of DNA - a structure that enables it to carry biological information from one generation to the next. Despite his scientific achievements, Dr. Scientist use the term "double helix" to describe DNA's winding, two-stranded chemical structure.
This shape - which looks much like a twisted ladder - gives DNA the power to pass along biological instructions with great precision. To understand DNA's double helix from a chemical standpoint, picture the sides of the ladder as strands of alternating sugar and phosphate groups - strands that run in opposite directions. Each "rung" of the ladder is made up of two nitrogen bases, paired together by hydrogen bonds.
Because of the highly specific nature of this type of chemical pairing, base A always pairs with base T, and likewise C with G. So, if you know the sequence of the bases on one strand of a DNA double helix, it is a simple matter to figure out the sequence of bases on the other strand.
DNA's unique structure enables the molecule to copy itself during cell division. When a cell prepares to divide, the DNA helix splits down the middle and becomes two single strands. These single strands serve as templates for building two new, double-stranded DNA molecules - each a replica of the original DNA molecule. In this process, an A base is added wherever there is a T, a C where there is a G, and so on until all of the bases once again have partners.
In some cases, one buffer is not optimal for both enzymes; in this case, you can digest your vector with the first enzyme using its optimal buffer, and then do an ethanol precipitation step as described in our previous answer before digesting your vector with the second enzyme in its optimal buffer.
As you may know, SAP treatment of any vector will decrease the efficiency of the ligation reaction. Also, even though you heat-inactivate the SAP, some residual activity often remains; this may lead to dephosphorylation of your insert and loss of ligation activity.
Therefore, you will likely have many more transformants after you skip the SAP treatment step. We hope this information has been helpful! And best of luck to you as you continue your cloning experiments! Dear sir, thanx for your valuable inputs and suggestions. Now, what should i do to concentrate my ligation mix?? Another problem, a bit weired, i am encountreing, i got blue white transformants once on my plate, ofcourse white colonies will be my interest, i checked them using PCR with my specific primers as well as M13 primers, and give me correct amplification, but i dont know somehow, the clones are unstable as after days if i grow them on lb amp plate, they show growth, but when i isolate plasmid using promega kit i gt only genomic DNA on gel and also smear pattern on gel after digestion.
I am really stuck here as firstly i hardly get any clones on plate after ligation and even if i gt some clones, they show me very weird pattern but at the same time they show correct amplification. Welcome back Anjali, Congratulations on your successful acquisition of white colonies — that is fantastic!
And better yet, your PCR reactions using gene-specific primers or M13 primers yield the expected amplification products. Despite your successes, you are now facing a new type of technical problem: your clones appear unstable, since your miniprepped plasmid DNA does not show up on an agarose gel either before or after you digest it with restriction enzymes.
Prior to digestion, your DNA is difficult to visualize. And after digesting the DNA, you see a smeared pattern on an agarose gel. How can you overcome these technical hurdles? Indeed, we have encountered a similar problem in the lab ourselves. When this happened to us, we discovered that some of the E. These endonucleases directly impact plasmid yield and stability when you carry out the DNA miniprep procedure.
We used two different approaches to overcome this issue. First, we used miniprep kits that include an extra wash step to inactivate endonucleases from the E. Second, we used a commercially available E. You could even use DH5alpha E. We hope they help you successfully isolate and digest your clones of interest. Best of luck to you! Check out the links below to learn more about alternative miniprep kits, E. Are viruses harmful to the respiratory system especially the airborne ones!
Hello Eva, Although there are many different types of viruses, your question deals primarily with respiratory viruses. As with other types of viruses, people of all ages can be infected with respiratory viruses; however, young children and elderly individuals are most at risk of experiencing severe symptoms and associated complications. What can you do to prevent or reduce your risk of being infected by these viruses?
One answer is to wash your hands frequently and thoroughly in order to prevent them from spreading. Vaccines are another preventative measure. However, although vaccines are available for some of these viruses e.
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