Which nucleic acid contains the sugar deoxyribose

The nucleotide is named according to the nitrogenous base it contains. The phosphate group of one nucleotide bonds covalently with the sugar molecule of the next nucleotide, and so on, forming a long polymer of nucleotide monomers. In its natural state, each DNA molecule is actually composed of two single strands held together along their length with hydrogen bonds between the bases.

Watson and Crick proposed that the DNA is made up of two strands that are twisted around each other to form a right-handed helix, called a double helix. Base-pairing takes place between a purine and pyrimidine: namely, A pairs with T, and G pairs with C. In other words, adenine and thymine are complementary base pairs, and cytosine and guanine are also complementary base pairs.

Adenine and thymine are connected by two hydrogen bonds, and cytosine and guanine are connected by three hydrogen bonds. The diameter of the DNA double helix is uniform throughout because a purine two rings always pairs with a pyrimidine one ring and their combined lengths are always equal. Figure 9. There is a second nucleic acid in all cells called ribonucleic acid, or RNA. Each of the nucleotides in RNA is made up of a nitrogenous base, a five-carbon sugar, and a phosphate group.

In the case of RNA, the five-carbon sugar is ribose, not deoxyribose. RNA nucleotides contain the nitrogenous bases adenine, cytosine, and guanine. Molecular biologists have named several kinds of RNA on the basis of their function. For this reason, the DNA is protected and packaged in very specific ways. In addition, DNA molecules can be very long. Stretched end-to-end, the DNA molecules in a single human cell would come to a length of about 2 meters.

Thus, the DNA for a cell must be packaged in a very ordered way to fit and function within a structure the cell that is not visible to the naked eye. The chromosomes of prokaryotes are much simpler than those of eukaryotes in many of their features Figure 9. Most prokaryotes contain a single, circular chromosome that is found in an area in the cytoplasm called the nucleoid. The size of the genome in one of the most well-studied prokaryotes, Escherichia coli, is 4.

So how does this fit inside a small bacterial cell? Each ribonucleotide base consists of a ribose sugar, a phosphate group, and a nitrogenous base. Adjacent ribose nucleotide bases are chemically attached to one another in a chain via chemical bonds called phosphodiester bonds.

Additionally, RNA contains ribose sugars rather than deoxyribose sugars, which makes RNA more unstable and more prone to degradation. RNA is then translated into proteins by structures called ribosomes. At this time it is possible a mutation may occur. A mutation is a change in the sequence of the nitrogen bases.

Most of the time when this happens the DNA is able to fix itself and return the original base to the sequence. However, sometimes the repair is unsuccessful, resulting in different proteins being created. DNA packaging is an important process in living cells. Without it, a cell is not able to accommodate the large amount of DNA that is stored inside. A eukaryote contains a well-defined nucleus, whereas in prokaryotes the chromosome lies in the cytoplasm in an area called the nucleoid.

In prokaryotic cells, both processes occur together. What advantages might there be to separating the processes? What advantages might there be to having them occur together?

Eukaryotic and prokaryotic cells : A eukaryote contains a well-defined nucleus, whereas in prokaryotes, the chromosome lies in the cytoplasm in an area called the nucleoid.

The size of the genome in one of the most well-studied prokaryotes, E. So how does this fit inside a small bacterial cell? The DNA is twisted by what is known as supercoiling. Supercoiling means that DNA is either under-wound less than one turn of the helix per 10 base pairs or over-wound more than 1 turn per 10 base pairs from its normal relaxed state.

Some proteins are known to be involved in the supercoiling; other proteins and enzymes such as DNA gyrase help in maintaining the supercoiled structure. Eukaryotes, whose chromosomes each consist of a linear DNA molecule, employ a different type of packing strategy to fit their DNA inside the nucleus.

At the most basic level, DNA is wrapped around proteins known as histones to form structures called nucleosomes.

The histones are evolutionarily conserved proteins that are rich in basic amino acids and form an octamer. The DNA which is negatively charged because of the phosphate groups is wrapped tightly around the histone core.

This nucleosome is linked to the next one with the help of a linker DNA. This is further compacted into a 30 nm fiber, which is the diameter of the structure. At the metaphase stage the chromosomes are at their most compact, approximately nm in width, and are found in association with scaffold proteins. Eukaryotic chromosomes : These figures illustrate the compaction of the eukaryotic chromosome.

In interphase, eukaryotic chromosomes have two distinct regions that can be distinguished by staining. The tightly packaged region is known as heterochromatin, and the less dense region is known as euchromatin.

Heterochromatin usually contains genes that are not expressed, and is found in the regions of the centromere and telomeres. The euchromatin usually contains genes that are transcribed, with DNA packaged around nucleosomes but not further compacted.

RNA is the nucleic acid that makes proteins from the code provided by DNA through the processes of transcription and translation. DNA is the genetic material found in all living organisms and is found in the nucleus of eukaryotes and in the chloroplasts and mitochondria.

In prokaryotes, the DNA is not enclosed in a membranous envelope. Each nucleotide is made up of three components: a nitrogenous base, a pentose five-carbon sugar called ribose, and a phosphate group.