What is the difference between a nucleotide, gene, and a chromosome?

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sciftw | High School Teacher | (Level 1) Educator Emeritus

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A nucleotide is a building block to DNA. The DNA contains genes, which are located on individual chromosomes. They are related, and you can't really have DNA without genes and for sure not without nucleotides.

A nucleotide is made of three basic pieces.  A phosphate, a five carbon sugar (deoxyribose), and one of four nitrogen bases. The phosphate and sugar stack on top of each other and the base sticks off the side of the sugar. It resembles the shape of an "L." That's a nucleotide. Another corresponding base would attach to the base and then be connected to the sugar with the phosphate on top. Now it should look like a "U" with a flat bottom. That's two nucleotides attached side by side. Stick another nucleotide pair beneath it and another and another and it starts looking like a ladder. Twist that ladder, and you have the double helix that is DNA.

If you made that DNA ladder 3 billion ladder "rungs" long, you would have a human DNA sequence. Divide that up into 46 chunks, and those are the chromosomes present in the human genome.  In other words a chromosome is a really long section of DNA, which is made of nucleotide units.

A gene is a smaller section of a chromosome. A different way to put it is that a gene is a smaller section of DNA, or a group of bases (which are a part of the nucleotide).

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tejastamboli | eNotes Newbie

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Nucleotide is basically one structural block of DNA. one single nucleotide is made up of a nitrogeneous base(any one of 4: adenine, thymine, cytosine, guanine), one molecule of phosphoric acid and 1 molecule of sugar. More than one nuceotide molecules linked together form one strand of DNA molecule, such 2 strands bonded with each other through H-bonds between their nitrogeneous bases make 1 molecule of DNA.

Gene is certain region(a bracket of more than 1 nucleotides) of the long nucleotide sequence responsible for manufacturing certain specific set of proteins carrying out a specific task.

Now, this DNA molecule does not prevail in an isolated independent form in a living organism's cells.Instead, this double stranded DNA molecule is wrapped with few other cohesive protein structures into a relatively robust structure, this structure is called chromosome. 

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olivera | eNotes Newbie

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A nucleotide is one of the structural components/building blocks, of DNA and RNA. They consist of a base (one of four chemicals: adenine, thymine, guanine, and cytosine) plus a molecule of sugar and one of phosphoric acid. Gene is a part/piece of your DNA that has instructions for making specific proteins which determine characteristics of offspring. A chromosome is a strand of DNA that carries genes and are generally found in the nucleus of cells.

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iamkaori | Student, Grade 9 | (Level 2) Salutatorian

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Nucleotides are the building blocks of DNA and RNA. They are composed of a nitrogenous base (cytosine, adenine, guanine, thymine, or urecil), 5-carbon sugar (ribose or deoxyribose), and one or more phosphate group(s). 

DNA can be found in chromosomes. Chromosomes are thread-like structures that have DNA coiled around histone (a protein). It usually looks like an x-shape.

Genes can be found on chromosomes. They are the characteristics that are coded by the DNAs to make each organism different. 

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