BLAST

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19

Chapter 2

CHAPTER 2

Biological Sequences

Sequence similarity is a powerful tool for discovering biological function. Just as the

ancient Greeks used comparative anatomy to understand the human body and lin-

guists used the Rosetta stone to decipher Egyptian hieroglyphs, today we can use

comparative sequence analysis to understand genomes, RNAs, and proteins. But why

are biological sequences similar to one another in the first place? The answer to this

question isn’t simple and requires an understanding of molecular and evolutionary

biology.

The Central Dogma of Molecular Biology

Most courses in molecular biology begin with the Central Dogma of Molecular Biol-

ogy, which describes the path by which information contained in DNA is converted

to protein molecules with specific functions. Stated simply, the Central Dogma is:

“from DNA to RNA to protein.” Figure 2-1 shows a more complete diagram of this

process and will be referenced throughout this section.

DNA

The hereditary material that carries the blueprint for an organism from one genera-

tion to the next is called deoxyribonucleic acid. It is much more commonly referred

to by its acronym, DNA. Every time cells divide, the DNA is duplicated in a process

called DNA replication. The entire DNA of an organism is called its genome, and

genomes ...