Replication, Transcription, Translation
Supplementary Material
Biological Molecules and Processes
1. DNA
2. RNA
3. Protein
Replication: 1 DNA molecule replicates
(doubles) into 2 identical DNA copies
Transcription: DNA molecule transcribed
(copied) into RNA molecule
Translation: RNA molecule translated (the code
is read and interpreted) to produce protein
Replication
When a cell divides,
the entire DNA
content in a cell
needs to replicate in
order for identical
DNA information to
be contained in
both cells
Transcription/Translation
Proteins need to be
created in cells to carry
out many cellular
functions, including
carry out reactions and
transport things
• Example: hemoglobin
is a protein that is
contained within red
blood cells and
delivers oxygen
throughout our
bodies
DNA/RNA molecules have 2 different
“ends”
The shape of DNA is a double helix. If you were to unwind it, you
would see two single strands of DNA that are connected by base
pairs (A pairs with T, G pairs with C). Each of these single strands
has a “LEFT” end and a “RIGHT” end.
The two single strands of DNA have opposite orientation. So one
strand reads from the “LEFT” end to the “RIGHT” end as you look
at the sequence horizontally across the page. The other strand
reads from the “RIGHT” end to the “LEFT” end
DNA
LEFT - TCCACAGTCTTG - RIGHT
RIGHT - AGGTGTCAGAAC - LEFT
Transcription
• As DNA is transcribed into RNA, complimentary bases are added. G pairs
with C (and vice versa), T pairs with A, A pairs with U
• Both single strands can be transcribed into RNA. The RNA is transcribed in
the LEFT to RIGHT orientation. *This means that bases are copied on the
DNA from the RIGHT end to the LEFT end. So when you are copying DNA
into RNA, start at the RIGHT end of the DNA strand and move toward the
left. However, the RNA you are writing starts at the LEFT end.
• Arrows indicate the direction of transcription
DNA
2nd RNA
UCAGAAC - LEFT
LEFT - TCCACAGTCTTG - RIGHT
RIGHT - AGGTGTCAGAAC – LEFT
LEFT - UCCACA
1st RNA
Transcription
After you copy the entire sequence, you will realize that each DNA
strand has a RNA copy in the same end to end orientation, only with
every T replaced by a U. We call the LEFT to RIGHT DNA strand the
coding strand for the Blue RNA sequence shown below. The RIGHT to
LEFT DNA strand is the coding strand for the Red RNA sequence.
RNA
DNA
RNA
RIGHT - AGGUGUCAGAAC - LEFT
LEFT - TCCACAGTCTTG - RIGHT
RIGHT - AGGTGTCAGAAC - LEFT
LEFT - UCCACAGUCUUG - RIGHT
Translation
• In translation, we read the RNA code
to determine what amino acids are
chained together to form protein. The
RNA is translated in the LEFT to RIGHT
orientation.
• Boxes indicate the first three RNA
bases that form a codon (CAA for the
red, UCC for the blue). The codon
table is used to determine what amino
acid is added
RIGHT - AGGUGUCAGAAC - LEFT
LEFT - UCCACAGUCUUG - RIGHT
Translation
• Arrows show the direction of
translation. Unlike transcription, the
amino acid sequence will be different
for the two RNA molecules depending
on which direction you are heading.
So it is important that you start
translation from the LEFT end of the
RNA sequence.
Gly - Cys - Asp - Gln
RIGHT - AGGUGUCAGAAC - LEFT
LEFT - UCCACAGUCUUG - RIGHT
Ser - Thr - Val - Leu
Practice Problems
You have unwound a double helix and exposed a single strand
with the following sequence and orientation:
LEFT – AGTTCATGCATCCGA – RIGHT
1) During DNA replication, the molecule will once again
become double stranded. Provide the correct sequence
and orientation to make a double stranded DNA helix.
2) Transcribe each strand of DNA to a molecule of RNA.
Draw an arrow to show the direction that transcription
proceeds
3) For each RNA molecule you made, translate it into the
correct amino acid sequence. Draw an arrow to indicate
the direction of transcription
Answers
1) LEFT – AGTTCATGCATCCGA – RIGHT
RIGHT – TCAAGTACGTAGGCT – LEFT
2) LEFT – AGUUCAUGCAUCCGA – RIGHT
RIGHT – UCAAGUACGUAGGCU – LEFT
3) Ser – Ser – Cys – Ile – Arg
STOP – Ala – Asp – Ser
Mutations
Two main types of mutations
1) Point mutations – when a single base is
substituted for a different base
LEFT - UCCACAGUCUUG - RIGHT
LEFT - UCCACCGUCUUG - RIGHT
1) Insertions/deletions – when single or
multiple bases are added/subtracted
LEFT - UCCACAGUCUUG - RIGHT
LEFT - UCCA_ _GUCUUG - RIGHT
LEFT - UCCAGUCUUG - RIGHT
Practice on Your Own!
Write out a random sequence of bases. This will represent
your RNA to be translated
1) Translate your sequence into a sequence of amino acids.
2) Use a single point mutation to change the sequence.
Does this affect the amino acid sequence? Which point
mutations will affect the sequence? Which mutations will
not? (Hint: think about what position the mutation is at in
the codon)
3) Try varying levels of insertions/deletions (indels) in your
sequence. What numbers of indels are most likely to
affect the amino acid sequence? What numbers of indels
are least likely to affect the amino acid sequence?