Transcript DNA and Translation Gene

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 nucleotides
• Each mRNA codon matches
with 1 of 20 amino acids
• Ribosome reads codons 1 at a
time
• Codon GUU = Valine
• Codon AUG = Methionine
(Start)
• Codons UAA or UAG or
UGA = Stop
• 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
• tRNA carries over the
• Translation begins
proper amino acid
when the mRNA
– tRNA anticodon
codon “AUG” is read
matches with the
by the ribosome
mRNA codon
• Each mRNA codon
•
One
by
one,
amino
acids
matches with a
are linked together
specific amino acid
• Translation ends when a
– AUG = methionine
“stop” codon is read by
– GCU = alanine
the ribosome
• End result: Polypeptide
(Protein)
Methionine
Proline
Serine
Proline
Glycine
tRNA
tRNA
tRNA
tRNA
tRNA
tRNA
UAC
GGC
UCA
GGU
CCU
AGA
Serine
GAU AUG CCG AGU CCA GGA UCU UGA
Ribosome
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
Quick Review
• Every DNA gene codes for a specific
protein
• Codon/anticodon match guarantees
proper amino acid
• Many amino acids link to make one
protein