DNA and Translation
• Gene: section of DNA that
creates a specific protein
– Approx. 25,000 human
genes
• Proteins are used to build cells
and tissue
• Protein synthesis involves two
processes:
1) Transcription
2) Translation
• Transcription takes place in the nucleus
– 1) DNA double helix is broken apart
– 2) mRNA nucleotides match up
– 3) Finished mRNA detaches, and moves to a
ribosome
• Codon: Combination of 3 mRNA
• AUG codon: Activates
nucleotides
the ribosome
(start codon)
• Each mRNA codon matches with 1
of 20 amino acids
• UAA or UAG or UGA
codon: deactivates the
• Ribosome reads codons 1 at a
ribosome (stop codon)
time
• Defined: Process of making proteins
– Step 1: mRNA enters ribosome
– Step 2: Ribosome reads one mRNA codon at a time
– Step 3: tRNA delivers amino acids until a protein is
created
Translation Details
• Translation begins when the mRNA codon “AUG” is
read by a ribosome
• Ribosome reads one codon at a time
AUG = methionine
GCU = alanine
• tRNA carries over the proper amino acid
– tRNA anticodon matches with the mRNA codon
– Prevents delivery of wrong amino acid
• One by one, amino acids are linked together
• Translation ends when a “stop” codon is reached
• What just happened?: A ribosome made a protein
Now the codon and
anticodon match. This
ensures
proper
Thisthe
is why
the
amino
acid (serine)
anticodon
is is
delivered.
important!
Because the codon and anticodon don’t match, the
wrong amino acid will not be delivered.
Questions to answer:
1) In order, list the amino acids that will be delivered to this ribosome.
2) What is the anticodon of each codon?
tRNA
tRNA
tRNA
tRNA
tRNA
tRNA
UAC
GGC
UCA
GGU
CCU
AGA
3) When finished, how many amino acids in size is this protein?
Methionine Proline
(MET)
(PRO)
ignore
Serine
(SER)
Proline
(PRO)
Glycine
(GLY)
Serine
(SER)
tRNA
tRNA
tRNA
tRNA
tRNA
tRNA
UAC
GGC
UCA
GGU
CCU
AGA
GAU AUG CCG AGU CCA GGA UCU UGA
start
Ribosome
stop
Practice Problem
Always use mRNA to find
the amino acid
DNA
mRNA
codon
tRNA
anticodon
Amino Acid
Practice Problem
Always use mRNA to find
the amino acid
DNA
mRNA
codon
tRNA
anticodon
Amino Acid
Practice Problem
Always use mRNA to find
the amino acid
DNA
mRNA
codon
tRNA
anticodon
C
C
A
G
G
U
C
C
A
Amino Acid
Review
1) Define transcription? Translation?
2) What are genes and how are they different from
chromosomes?
3) How many nucleotides make a codon?
4) The anticodon can be found on which object?
5) The anticodon must match the ______.
6) Place the following steps in order from start to finish:
a. Proteins are assembled
b. Ribosome reads a codon one at a time
c. mRNA arrives at the ribosome
d. tRNA delivers amino acids to the ribosome
7) Be able to solve practice problems similar to the three
examples on slides #8-11.
mRNA codes