1. Ch.6s.2 Genetics: Protein Synthesis
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The order of nucleotide bases in a strand of DNA is the DNA sequence -instructions for the cell
A sequence of 3 nucleotide bases (codon) is an instruction to add one particular amino acid, (from the twenty possible) at that location, to a protein chain
Proteins are long chains of amino acids in a sequence determined by the sequence of codons in a gene
DNA sequence
Codon
Amino acid
protein

2. Ch.6s.2 Genetics: Protein Synthesis
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Characteristics
Protein synthesis
Transcription
mRNA
translation
Proteins act as chemical messengers and cause characteristics: shapes, sizes, colors and textures of an organism
Protein synthesis includes two steps: transcription of a gene into a strand of messenger RNA (mRNA)
translation of an mRNA strand into a protein

3. Ch.6s.2 Genetics: Protein Synthesis
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Transcription:
in the nucleus, helicase separates complementary base pairs on the two strands of a gene
RNA polymerase attaches free RNA nucleotides to template strand DNA form a primary RNA transcript
this transcript is modified to become the completed mRNA strand
mRNA travels through a nuclear pore out to the cytoplasm
Helicase
RNA polymerase
Primary RNA transcript
mRNA
cytoplasm

4. Ch.6s.2 Genetics: Protein Synthesis
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RiboNucleic Acid
Ribose
Uracil (U)
Nucleus
RNA stands for RiboNucleic Acid.
RNA is made from DNA, but…
RNA has a different type of sugar (ribose not deoxyribose)
RNA is a single strand
RNA has uracil (U) not thymine (T)
DNA never leaves the nucleus

5. The DNA to RNA base-pairing rules are (DNA – RNA) A – U T -- A C – G
Ch.6s.2 Genetics: Protein Synthesis
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DNA to RNA base-pairing rules
(NEW ONES!)
mRNA
tRNA
rRNA
The DNA to RNA base-pairing rules are (DNA – RNA)
A – U
T -- A
C – G
G – C
Three types of RNA:
Messenger RNA (mRNA)
transfer RNA (tRNA)
ribosomal RNA (rRNA)

6. Ch.6s.2 Genetics: Protein Synthesis
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Translation:
In the cytoplasm, ribosomal subunits form around one end of the mRNA strand
A tRNA with an anticodon complementary to the first mRNA codon bonds
The next complementary tRNA attaches to the next mRNA codon and attaches its amino acid to the first amino acid
Complementary tRNAs continue attaching their amino acids to the protein chain
Ribosomal subunits
tRNA anticodon
protein

7. Ch.6s.2 Genetics: Protein Synthesis
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Mutation
insertion
deletion
substitution
translocation
Mutations occur when there is a change in the order of bases in a DNA strand
An insertion occurs when an extra nucleotide is added
A deletion occurs when a nucleotide is deleted
A substitution occurs when one nucleotide is replaced with a different nucleotide
Translocation occurs when part of the DNA sequence moves to another location

8. Ch.6s.2 Genetics: Protein Synthesis
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Repair enzymes
Fixed
No change in protein
Negative change
Positive change
mutagen
Repair enzymes normally fix mutations
if mutations are not fixed, 3 consequences could occur
Changes in DNA may not cause any change in the protein (most common)
Changes in DNA may cause a negative change in protein
Changes in DNA may cause a positive change in protein
A mutagen is anything that causes a mutation in DNA
Radiation, chemicals