1. A molecule of DNA consists of 2 strands that create a dual helix framework.

You are watching: Why is dna called the blueprint for life

DNA is a macromolecule consisting of two strands that twist approximately a common axis in a shape dubbed a double helix. The double helix looks favor a twisted ladder—the rungs of the ladder are created of pairs of nitrogenous bases (base pairs), and the sides of the ladder are comprised of alternating sugar molecules and also phosphate groups.

Molecules of DNA variety in length from numerous thousands to countless base pairs. The smallest chromosome in the huguy genome, Chromosome 21, has around 48 million base pairs.


A molecule of DNA has actually two strands, composed of nucleotides, that develop a dual helix form.

Downpack DNA Lab Activities

2. Each DNA strand also is created of nucleotides—units made up of a sugar (deoxyribose), a phosphate team, and also a nitrogenous base.

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

The sugar in DNA’s nucleotides is dubbed deoxyribose—DNA is an abbreviation for deoxyribonucleic acid. RNA molecules usage a different sugar, called ribose. Covalent bonds sign up with the sugar of one nucleotide to the phosphate group of the following nucleotide, creating the DNA strand’s sugar-phosphate backbone.

A nitrogenous base is an organic molecule that consists of nitrogen and also has the chemical properties of a base. Tright here are four nitrogenous bases that take place in DNA molecules: cytosine, guanine, adenine, and also thymine (abbreviated as C, G, A, and also T). RNA molecules contain cytosine, guanine, and also adenine, yet they have actually a different nitrogenous base, uracil (U) rather of thymine.


3. The sequences of nitrogenous bases on the 2 strands of a DNA molecule are complementary.

The sequence of nitrogenous bases on one strand also of a DNA molecule’s double helix matches up in a certain method with the sequence on the various other strand also. Adenine pairs through thymine and also cytosine pairs via guanine.

Why carry out the nitrogenous bases pair in this specific way? The bases on each strand are joined to the bases on the various other strand through hydrogen bonds, however different bases have various chemical structures. Cytosine and thymine (and also uracil in RNA) are pyrimidines, containing one ring. Adenine and also guanine are purines, containing two rings. The pyrimidines pair with the purines: cytosine and guanine create 3 hydrogen bonds, and also adenine and thymine create 2.

4. Specific sequences of nitrogenous bases that code for certain proteins or regulatory RNA molecules are dubbed genes.

Each strand also of DNA is like a recipe book for manufacturing proteins. Certain sequences of nitrogenous bases alengthy the strand encode certain RNA molecules. These sequences are called genes. mRNA molecules transcribed from genes are interpreted into proteins later.

Chromosomes can vary widely in their number of base pairs and also genes. The longest chromosome in human cells, Chromosome 1, is approximately 249 million base pairs lengthy and also has actually in between 2000 and 2100 distinctive genes. Chromosome 21, the shortest huguy chromosome, consists of 48 million base pairs and also contains between 200 and 300 genes. Overall, prokaryotic cells have actually shorter chromosomes through fewer genes. For instance, the bacterium Carsonella rudii has actually only 159,662 base pairs and 182 genes in its whole genome.

Although genes gain many of the credit for what DNA does, they make up only around 1% of DNA (in humans). Genes are separated from one one more by sequences of nitrogenous bases that don’t carry out instructions for RNA synthesis. These are called intergenic regions. Even within genes, there are regions of noncoding DNA dubbed introns.

See more: What Do You Call Someone Who Inspires You, What Do You Call Someone That Inspires Others

Noncoding areas of DNA are essential because they carry out binding sites for proteins that aid activate or deactivate the process of transcription. They have the right to also carry out defense for the coding regions. For instance, telomeres consist of repeated sequences that protect the hereditary indevelopment on each DNA molecule from being damaged during cell department.