1. Translation
Once outside of the nucleus, the mRNA strand is
Translated into an amino acid.
Start codon. Each codon codes for an amino acid. This
three letter sequences “tells” the ribosome to start
creating a polypeptide (lots of amino acids linked
together).

2. Codons & Translation
 Each codon = 1
amino acid.
 A codon is made up
of 3 bases (letters).
 There are 20 amino
acids, but there are
multiple codons for
each amino acid.

3. Codons & Translation
2ND LETTER
 This is a codon chart.
1ST
 The 20 amino acids 3RD
are represented by L
the different colored E L
T E
circles. T
T
 The amino acids E T
have different R E
characteristics like R
positive or negative
charges,
hydrophobic, or

4. Quick Ribosome Review
 Ribosomes make
proteins
 Located throughout the
cell and on the ER.
 Have 2 parts:
 Large subunit
 Small subunit
 mRNA is “sandwiched”
between the large and
small subunits.

5. Translation
The large ribosomal subunit (LRS)
has 3 binding sites: E,P, and A.
The mRNA joins the small
ribosomal subunit (SRS) at the
5’ untranslated region.

6. Translation
The LRS attaches to the SRS
so the first codon lines up
with the P-binding site.

7. Translation
A tRNA (transfer RNA)
carrying the amino acid
Met attaches to the start
codon (AUG).
This starts elongation
(making the protein).

8. Translation
What does GAC code for?

9. How does the ribosome “know” to
stop adding amino acids?
 There is a STOP
codon.
 When the ribosome
reaches this codon it
stops adding amino
acids and falls away
from the polypeptide.
 Translation is now
complete!

10. Information on Translation
 To practice transcribing and translating your
own protein click here.
 For a detailed description and images for
translation click here.
 To learn about mutations that can occur
during transcription and translation keep
reading!

11. Now it’s your turn..
 You should be able to use the notes you took
for homework to complete the questions up
through the elongation stage of translation.
 Remember: There are lots of resources on the
blog to help you!

12. Mutation
Is this what you
think of when you
think of
mutation?

13. Mutation: Fact & Fiction
 FICTION
All mutations are bad…………………….
 Mutations are a source of evolution… FACT
 Mutation can be silent……………………
FACT
 Mutations only happen when DNA is exposed to
things like radiation………………………..
FICTION

14. Fiction #1:
All mutations are bad
 Sickle Cell Anemia:
 Replacement of A with T at the 17th nucleotide in
a beta chain of hemoglobin.
 The mutation changes from GAG (glutamic acid)
to GTG (valine).
 People with sickle cell anemia are resistant to
malaria (very helpful in areas with a high rate of
the disease).

15. Fact #1:
Mutations are a source of evolution
 All new genetic
variation comes
from mutation.
 Antibiotic resistance
 Peppered Moth?

16. Fact #2:
Mutations can be silent
 Most amino acids
are encoded by
several different
codons.
 A mutation at the 3rd
codon is likely to
have little effect.

17. Fiction #2:
Mutations only happen when DNA is
exposed to things like radiation.
 Environmental
causes are a source
of mutation, but not
the only source.
 Mutations can also
occur when the DNA
is being copied for
cellular division.

18. Types of Mutations
 Single Base substitutions
 Insertions and Deletions
 Duplications
 Translocations

19. Single base substitutions
 A is substituted for T
and vice versa.
 C is substituted for G
and vice versa.
 These subst. are not
as detrimental as non-
pair substitutions (e.g.:
T for C).

20. Insertions and Deletions
 Insertion: a base
pair is added to the
DNA.
 Deletion: a base pair
is subtracted from
the DNA.
 This shifts the
reading frame for
the codons.
Huntington Disease Fragile X

21. Duplications
 Doubling of a section
of the genome.
 Duplicates can be be
beneficial.
 Over time, duplicates
can acquire new
function.

22. Translocations
 Translocations are
the transfer of a
piece of one
chromosome to a
nonhomologous
chromosome.
 Translocations are
often reciprocal; that
is, the two
nonhomologues
swap segments.

23. Are all mutations passed on to the
next generation?
Germline Mutations:
Somatic Mutations:
• Found in every cell • Occur in non-reproductive body
descended from the cells (bone marrow, liver, etc.)
zygote (fertilized egg
& sperm).
• Mutation does NOT get passed
• Mutation CAN be onto the offspring.
passed onto the
offspring.