What type of bases are adenine and guanine

And those nucleotides always pair. We also count DNA and the amount of DNA, or the length of DNA by using units of base pairs, so if we're discussing a gene and we want to describe how big is a gene, we might say that the gene is a thousand base pairs long. If it's a really big gene, it may be 10, base pairs, or essentially 10 kilobases long.

Lawrence C. Brody, Ph. Delete Cancel. Adenine, thymine, cytosine and guanine are the four nucleotides found in DNA. This image is linked to the following Scitable pages:. Traits as diverse as the color of a person's eyes and the scent of a rose are determined by the information contained in DNA.

Learn how this information is coded by strings of molecules called nucleotides. Knowing this order is the first step in our efforts to map the DNA sequences of all organisms and thereby connect gene sequence with gene function. Comments Close. The Comment you have entered exceeds the maximum length. Submit Cancel. Comments Please Post Your Comment. The lightly staining regions usually contain genes that are active, with DNA packaged around nucleosomes but not further compacted.

Concept in Action. Watch this animation of DNA packaging. The DNA molecule is a polymer of nucleotides. Each nucleotide is composed of a nitrogenous base, a five-carbon sugar deoxyribose , and a phosphate group. There are four nitrogenous bases in DNA, two purines adenine and guanine and two pyrimidines cytosine and thymine.

A DNA molecule is composed of two strands. Each strand is composed of nucleotides bonded together covalently between the phosphate group of one and the deoxyribose sugar of the next. From this backbone extend the bases. The bases of one strand bond to the bases of the second strand with hydrogen bonds. Adenine always bonds with thymine, and cytosine always bonds with guanine. The bonding causes the two strands to spiral around each other in a shape called a double helix.

Ribonucleic acid RNA is a second nucleic acid found in cells. RNA is a single-stranded polymer of nucleotides. It also differs from DNA in that it contains the sugar ribose, rather than deoxyribose, and the nucleotide uracil rather than thymine. Prokaryotes contain a single, double-stranded circular chromosome. Eukaryotes contain double-stranded linear DNA molecules packaged into chromosomes. The DNA helix is wrapped around proteins to form nucleosomes.

The protein coils are further coiled, and during mitosis and meiosis, the chromosomes become even more greatly coiled to facilitate their movement. Chromosomes have two distinct regions which can be distinguished by staining, reflecting different degrees of packaging and determined by whether the DNA in a region is being expressed euchromatin or not heterochromatin.

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