From DNA to protein

We said that the DNA codes for proteins. How does this work?

Proteins, like DNA, are long chains of building blocks. In proteins, there are 20 building blocks called amino acids.

DNA has 4 types of bases, so if one base coded for one amino acid, we would only be able to have 4 types of amino acid.

If a pair of bases codes for one amino acid, we would be able to have 4x4 (=16) amino acids.

If a group of three bases codes for one amino acid, we would be able to have 4x4x4 (=64) amino acids.

This table shows the genetic code:

Code	Amino acid	Code	Amino acid	Code	Amino acid	Code	Amino acid
TTT	F	TCT	S	TAT	Y	TGT	C
TTC	F	TCC	S	TAC	Y	TGC	C
TTA	L	TCA	S	TAA	stop	TGA	stop
TTG	L	TCG	S	TAG	stop	TGG	W
CTT	L	CCT	P	CAT	H	CGT	R
CTC	L	CCC	P	CAC	H	CGC	R
CTA	L	CCA	P	CAA	Q	CGA	R
CTG	L	CCG	P	CAG	Q	CGG	R
ATT	I	ACT	T	AAT	N	AGT	S
ATC	I	ACC	T	AAC	N	AGC	S
ATA	I	ACA	T	AAA	K	AGA	R
ATG	M	ACG	T	ACA	K	AGA	R
GTT	V	GCT	A	GAT	D	GGT	G
GTC	V	GCC	A	GAC	D	GGC	G
GTA	V	GCA	A	GAA	E	GGA	G
GTG	V	GCG	A	GAG	E	GGG	G

Each of the 20 amino acids has a 1-letter abbreviation for its name: A alanine, C cysteine, D aspartic acid, E glutamic acid, F phenyl-alanine, G glycine, H histidine, I isoleucine, K lysine, L leucine, M methionine, N asparagine, P proline, Q glutamine, R arginine, S serine, T threonine, V valine, W tryptophan, Y tyrosine.

On the Next Page we will use a simplified genetic code and see if we can decode what it means.