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

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DNA is a macromolecule consists of two strands the twist roughly a usual axis in a shape dubbed a double helix. The dual helix looks favor a twisted ladder—the rungs of the ladder are composed of pairs of nitrogenous bases (base pairs), and also the sides of the ladder are made up of alternate sugar molecules and phosphate groups.

Molecules that DNA range in length from numerous thousands to countless base pairs. The the smallest chromosome in the human genome, Chromosome 21, has approximately 48 million basic pairs.


A molecule of DNA has two strands, composed of nucleotides, that type a double helix shape.

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2. Each DNA strand is written of nucleotides—units comprised of a sugar (deoxyribose), a phosphate group, and also a nitrogenous base.

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

The street in DNA’s nucleotides is called deoxyribose—DNA is one abbreviation for deoxyribonucleic acid. RNA molecules usage a different sugar, referred to as ribose. Covalent bonds sign up with the sugar of one nucleotide come the phosphate team of the following nucleotide, forming the DNA strand’s sugar-phosphate backbone.

A nitrogenous base is an essential molecule that has nitrogen and has the chemical properties of a base. There are four nitrogenous bases that happen in DNA molecules: cytosine, guanine, adenine, and thymine (abbreviated as C, G, A, and T). RNA molecule contain cytosine, guanine, and adenine, but they have a various nitrogenous base, uracil (U) instead of thymine.


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

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

Why execute the nitrogenous bases pair in this details way? The bases on each strand are joined come the bases ~ above the other strand v hydrogen bonds, yet different bases have different chemical structures. Cytosine and thymine (and uracil in RNA) space pyrimidines, containing one ring. Adenine and guanine space purines, containing two rings. The pyrimidines pair v the purines: cytosine and also guanine form three hydrogen bonds, and adenine and also thymine type two.

4. Certain sequences that nitrogenous bases that password for details proteins or regulation RNA molecule are dubbed genes.

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

Chromosomes can vary extensively in their number of base pairs and genes. The longest chromosome in human being cells, Chromosome 1, is around 249 million basic pairs long and has between 2000 and 2100 unique genes. Chromosome 21, the shortest human chromosome, is composed of 48 million basic pairs and contains in between 200 and 300 genes. Overall, prokaryotic cells have much shorter chromosomes with fewer genes. For example, the bacter Carsonella rudii has actually only 159,662 basic pairs and 182 genes in its whole genome.

Although genes obtain most of the credit for what DNA does, they make up only around 1% that DNA (in humans). Genes are separated from one another by sequences of nitrogenous bases the don’t administer instructions for RNA synthesis. These are dubbed intergenic regions. Also within genes, over there are areas of noncoding DNA referred to as introns.

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Noncoding regions of DNA room important due to the fact that they administer binding sites because that proteins that aid activate or deactivate the process of transcription. They can also administer protection for the coding regions. Because that instance, telomeres consist of repeated sequences that safeguard the genetic information on every DNA molecule from being damaged during cell division.