What’s the difference between DNA, a genome, and a chromosome?

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What’s the difference between DNA, a genome, and a chromosome?

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They can be represented by a book analogy.

DNA pairs are individual alphabet letters.

3 DNA pairs make up a triplet representing words in a book.

Genes are chapters of a book made up of DNA triplets.

A chromosome is a book containing many genes.

A genome is a complete set of chromosomes like a complete encyclopedia book set.

Let’s start from the smallest building blocks. We can put a nucleobase (flavor A, T, C or G) together with a deoxyribose sugar to form a nucleoside. If we then attach a phosphate group to the ribose part of our nucleoside, it becomes a nucleotide capable of linking to others like it; deoxyribose alone won’t link to other deoxyriboses, so we need phosphates between them. Once you have several nucleotides connected to each other, you refer to the whole thing as **DNA** — deoxyribonucleic acid. It looks something like [this](https://humanbiology.pressbooks.tru.ca/wp-content/uploads/sites/6/2020/01/DNA.png). And since the nucleobases (the A/T/C/G parts) like to bind to each other, specifically A-T and C-G, two pieces of DNA will line up together like that. Complicated chemistry stuff means that lining-up happens at a slight angle, and that causes the typical double helix structure.

So that’s DNA. In living organisms, their total DNA isn’t just one long strand (double helix!); it’s divided into a number of separate strands. These are **chromosomes**, and in addition to just the strand of DNA, they also contain proteins named histones which the DNA is kind of wrapped around to help keep it organized. Humans have 23 unique chromosomes, and two of each (one from their mother, one from their father).

Then, the **genome** is pretty easy. It’s just the collective of genetic material (= DNA) in a person. It can also refer to the species as a whole, i.e. “the human genome is divided over 23 chromosome pairs”. That’ll usually be obvious from context.

DNA is a chemical. It’s got a structure that allows any molecule to be of arbitrary length, and to encode information by varying the exact composition along the strand.

A genome is the full set of genes of an organism. These genes are encoded in the DNA.

A chromosome is a physical structure found in cells, consisting of DNA coiled up on itself. In most organisms these come in pairs, and each pair contains the same genes (but with variations between them).

DNA is like a language. Each nirogen base (adenine guanine cytosine and thymine or uracil in RNA) is like a letter and put alot toghether into a sequence and you’ll get words and sentences. That can be used as instructions

A Chromosome is like two very very very long strands of that DNA but crumpled together into a thick rod. Think of it like a book.

A genome is the sum of chromosomes that an entire species share

DNA is a chemical. It’s a long chain of simpler units called “nucleotides” (four kinds: Adenine, Cytosine, Guanine, and Thymine) linked together by a sugar (ribose) and phosphate (phosphorous atom with 4 oxygen atoms).

A chromosome is made of two DNA chains that are complementary, meaning they run in opposite directions, and the nucleotides mirror each other (an Adenine on one strand has a Thymine opposite, a Cysteine has a Guanine opposite it).

A genome means “all the genetic material in a cell”. It can mean all the chromosomes / DNA in a specific cell, it can mean all of it in an organism (knowing there may be small differences between cells), or it may mean the DNA found in cells of a particular species (again, with the understanding that there’s differences between individuals).