16. DNA Double Helix
T A C G C A T C T A T G G C A G G G C T G C G T C A A A C T
A T G C G T A G A T A C C G T C C C G A C G C A G T T T G A
RNAP binds to promoter region
41. RIBOSOME
mRNA STRAND
A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
rRNA forms ribosome
42. mRNA STRAND
A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
START CODON STOP CODON
mRNA binds to ribosome (AUG)
43. mRNA STRAND
A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
U A C tRNA
Anti-codon
Amino tRNA brings in the anti-codon
Acid
44. mRNA STRAND
A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
G C A
PEPTIDE BOND
Amino Acid attached to tRNA binds with a peptide bond
45. A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
U C U
46. A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
A U G
47. A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
G C A
48. A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
G G G
49. A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
C U G
50. A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
C G U
51. A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
C A A
52. Ribsome hits stop codon and completes the
protein
A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
A C U
53. A U G C G U A G A U A C C G U C C C G A C G C A G U U U G A
1 2 3 4 5 6 7 8 9 10
Methionine Arginine Arginine Aspartic acid Valine
1 2 3 4 5 6 7 8 9 10
Arginine Tyrosine Proline Alanine Stop
54.
55. Summary
• There are two steps to creating proteins in a cell. These two steps are transcription and
translation. During transcription, which is the first step, RNA polymerase in the nucleus attaches to
DNA and unwinds it. The RNA polymerase then binds to the promoter region. The start codon tells
the RNA polymerase which gene it should replicate to get a specific protein. The RNA polymerase
reads the code that DNA stores and makes an RNA strand using the information. The only
difference between these strands (besides the fact that the mRNA strand is complementary to the
DNA one so the nucleotides are reversed) is that instead of using thymine, or T, RNA strands uses
uracil, or U. The mRNA strand is released from the DNA strand as soon as it hits the stop codon
which symbolizes the end of the gene. The mRNA then slips though the holes that allow things to
travel in and out of the nucleus. DNA needs mRNA because it is to big to slip through these holes
while mRNA can. The mRNA goes out into the cytoplasm. The next step is translation. In the
cytoplasm rRNA forms ribosomes; which bind to the mRNA strand and the start codon. Once the
ribosome is bound tRNA brings anticodons to the mRNA strand. An amino acid attached to tRNA
forms a peptide bond with other amino acids on other tRNA. The tRNA starts to fall off as new ones
attach, leaving the amino acid strand behind. Once the ribosome hits the stop codon the process
stops and the amino acid chain is left over. Depending on what amino acids there are in the chain
the protein will fold up in a specific way and form a new protein. You can get multiple proteins from
one mRNA strand by reusing it. That would be a lot of DNA coding for just one protein per time!
