The amount of guanine in an organism always equal the amount of?
cytosine.they form 3 hydrogen bonds between them.guanine always pairs with cytosine while adenine with thymine forming 2 hydrogen bonds.
The DNA of an organism has thymine as 20% of its bases. What percentage of its bases would be guanine?
B. 30% If thymine is 20%, then its compliment, adnine would be 20% for a total of 40%. The total for all four bases must be 100%. Thus, there is 60% of the bases remaining for cytosine and guanine and that would be divided evenly. So, cytosine and guanine would be 30% each.
Why might an organism have more guanine than cytosine?
There are four nitrogenous organic bases (hereinafter just called bases) found in deoxyribonucleic acid (DNA). DNA consists of two strands. The bases in one strand pair up with bases in the other strand. Wherever there is adenine in one strand there will be thymine in the other. Cytosine in one strand always pairs with guanine in the other strand. Guanine in one strand always pairs with cytosine in the other strand. Thymine in one strand always pairs with adenine in the other strand. Therefore, the quantity of cytosine and guanine should be the same. I can think of one circumstance when there could be more guanine than cytosine. This would be if a mutation occurred and there was one or nucleotides with guanine as their base in a strand where there shouldn't be guanine. Of course, ribonucleic acid is single-stranded. So molecules of mRNA, rRNA and tRNA could have more nucleotides with guanine as their base than nucleotides with cytosine.
Why does cytosine bond only with guanine?
It's most probably the steric hindrances between the bases that simply do not allow the bonding to take place. If they do accidentally bond with the wrong base then it won't be a stable structure and break. Also in DNA replication there are so many error correcting processes that occur. If a mistake happens it will get corrected immediately. Purine bases only join to pyrimidine bases. Purines have 2 rings whereas pyrimidines have just 1 ring.
Why does adenine combine with thymine only and not cytosine?
The base pairing rule of adenine bonding with thymine only and guanine with cytosine only (in DNA) can be clearly understood by carefully looking at the structure of these nitrogenous bases.Adenine and guanine are purines and cytosine and thymine are pyrimidines.The purines have an imidazole ring attached to the pyrimidine ring in their general structure. Now in ds DNA their is only enough space between the two strands to accommodate a purine and a pyrimidine. Two purines will not fit between the strands while two pyrimidines will be too far to bond. Therefore a purine has to make a hydrogen bond with another pyrimidine.Now looking at adenine we see two possible sites for making hydrogen bonds, N1 and amino group. In order to make H bond with the both we require a hydrogen attached to an electronegative atom as well as an electronegative atom both in a particular configuration. These conditions are met by thymine and not cytosine. So N1 of adenine bonds with hydrogen of N3 and amino group hydrogen with oxo group of thymine.Applying similar analysis to guanine, only cytosine can make hydrogen bonds with it in the ds DNA allowing the structure of DNA as seen.Hence adenine makes hydrogen bonds with thymine and guanine makes hydrogen bonds with cytosine.
Why is the proportion of Adenine and Guanine approximately equal to that of Thymine and Cytosine in the table?
The first one is easy: A always pairs with T, and C always pairs with G. (almost always, but let's not worry about mutation yet) So, since this is the case, then your proportion of A will equal your proportion of T, and your C will be proportionate to G. In the final analysis, the percentage of A/C and G/T in a particular organism's DNA will be approximately the same (because the DNA differences between members of a species are so small as to not make a difference in this calculation) The reason that this isn't true in RNA is because RNA has been stripped of non-coding regions (introns) that change the overall makeup of the sequence -- removing different portions, often depending on which gene product is desired (a single mRNA can be spliced to form many final products that code for different proteins, or subsets of a type of protein); therefore, the A/G C/U proportion will be sometimes radically altered. As for C), the thing about this is more of an evolutionary type question. Despite the fact that sharks are physiologically (or phenotypically) very different from squirrels, their DNA is not all that much different in a purely analytical sense -- it does not take a large change in the coding sequences to make something look (and act) totally different from it's progenitor. I would guess that this might indicate a common ancestor, but honestly -- it might also just be coincidence, as there is a limit to how much those ratios can change (the GC content is also critical to the ability of DNA to separate for duplication, so the amount this can decrease/increase does have a limit) Oh, also: I just noted that your table shows mRNA for two (shark and squirrel), and DNA for the third. Sneaky, and from my point of view, somewhat unfair, since human DNA is about 30 percent A/T and 20 percent C/G (which looks like your numbers up there, doesn't it?). IMHO, this is a rather rotten assignment.
Why does adenine pair with thymine and not cytosine?
adenine and guanine are called "purines" and cytosine, thymine and uracil are all "pyrimidines". purines must pair with a pyrimidine, they cannot pair with other purines for the reasons in the answer above mine. Also, purines are smaller than pyrimidines, so if you can imagine two purines pairing on dna it would pull the two strands too close to each other, while two pyrimidines would cause the strands to be too far apart and the structure of DNA just wouldn't work and we'd all be non existing.
Adenine and guanine are called?
Purine. For sure. Because Adenine and Guanine are purines. Cytosine and Thymine are pyrimidines. If this question was asking whether or not they are nitrogenous bases, it would have asked "What are adenine, guanine, cytosine and thymine called?" If it specifically targets at adenine and guanine, it means it's asking for their biochemical properties.
How are DNA of different organisms different?
In simple terms, Dna is made of 4 components A, G, T , C.A is for adenosineG for guanineT for thymineC for cytosineThese are nitrogenous bases. Now coming back to your question. It's the arrangement of these nitrogenous bases which makes up an organism. How? Dna codes for proteins. Most of the stuff in your body are proteins. These proteins take care of your day to day function of your body.Variability of dna in different organism is caused by-Length of the DnaChanges in sequences of A, G, T, CMutations (not the X-men type)Environmental factorsReplication errorThese changes in dna lead to events called speciation. And such speciation events lead to formation of newer species who may or may not be more suited to survive in that specific environment. That is the reason why there are so many species with different sets of Dna.Hope this helped.Up vote below
If a DNA strand contains 20% guanine, then how much will be adenine?
If by DNA strand you mean somehow the DNA helix got stripped and it somehow exist as a single strand, there is no way of knowing how much adenine there is based on the amount of guanine. The single strand could have any amount of adenine depending on what else is in its composition.If, however, the DNA strand is existing as a double helix as we expect it to then; Guanine pairs with Cytosine. Thus there is logically equal amounts of the two. Therefore G =20% and C =20%Leaving 60% to be divided equally between A and T given that A pairs T.