1. A molecule the DNA is composed of 2 strands that form a twin helix structure.

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DNA is a macromolecule consist of of 2 strands that twist about a typical axis in a shape called a double helix. The dual helix looks prefer a twisted ladder—the rungs the the ladder space composed of pairs of nitrogenous bases (base pairs), and the political parties of the ladder are comprised of alternate sugar molecules and phosphate groups.

Molecules of DNA selection in size from hundreds of thousands to countless base pairs. The smallest chromosome in the human genome, Chromosome 21, has approximately 48 million basic pairs.


A molecule of DNA has two strands, created of nucleotides, that form a dual helix shape.

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2. Every DNA strand is created of nucleotides—units consisted of of a sugar (deoxyribose), a phosphate group, and a nitrogenous base.

Each strand of DNA is a polynucleotide created of units referred to as nucleotides. A nucleotide has actually three components: a street molecule, a phosphate group, and a nitrogenous base.

The sugar in DNA’s nucleotides is called deoxyribose—DNA is an abbreviation because that deoxyribonucleic acid. RNA molecules use a different sugar, dubbed ribose. Covalent bonds join the street of one nucleotide to the phosphate team of the next nucleotide, forming the DNA strand’s sugar-phosphate backbone.

A nitrogenous base is an essential molecule that has nitrogen and has the chemistry properties that a base. Over there are four nitrogenous bases that occur in DNA molecules: cytosine, guanine, adenine, and thymine (abbreviated together C, G, A, and also T). RNA molecules contain cytosine, guanine, and also adenine, however they have a various nitrogenous base, uracil (U) rather of thymine.


3. The assignment of nitrogenous bases on the two strands that a DNA molecule are complementary.

The sequence of nitrogenous bases on one strand of a DNA molecule’s dual helix matches up in a particular method with the succession on the various other strand. Adenin pairs with thymine and cytosine pairs v guanine.

Why perform the nitrogenous bases pair in this details way? The bases on every strand are joined come the bases top top the various other strand through hydrogen bonds, but different bases have different chemical structures. Cytosine and also thymine (and uracil in RNA) room pyrimidines, include one ring. Adenine and also guanine room purines, containing 2 rings. The pyrimidines pair through the purines: cytosine and also guanine kind three hydrogen bonds, and adenine and thymine type two.

4. Particular sequences that nitrogenous bases that code for details proteins or regulatory RNA molecule are dubbed genes.

Each strand of DNA is favor a recipe book for manufacturing proteins. Details sequences the nitrogenous bases follow me the strand encode particular RNA molecules. These sequences are dubbed genes. MRNA molecule transcribed from genes are interpreted into protein later.

Chromosomes can vary widely in their number of base pairs and also genes. The longest chromosome in person cells, Chromosome 1, is around 249 million basic pairs long and has between 2000 and also 2100 distinctive genes. Chromosome 21, the shortest person chromosome, consists of 48 million base pairs and contains between 200 and 300 genes. Overall, prokaryotes cells have much shorter chromosomes with fewer genes. For example, the bacter Carsonella rudii has actually only 159,662 basic pairs and 182 gene in its entire genome.

Although genes obtain most that the credit for what DNA does, they make up only about 1% that DNA (in humans). Genes are separated native one an additional by assignment of nitrogenous bases the don’t provide instructions because that RNA synthesis. This are referred to as intergenic regions. Even within genes, over there are regions of noncoding DNA called introns.

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Noncoding regions of DNA room important because they carry out binding sites for proteins that help activate or deactivate the procedure of transcription. They deserve to also carry out protection because that the coding regions. Because that instance, telomeres consist of of repetitive sequences that defend the hereditary information on every DNA molecule from gift damaged throughout cell division.