Download transcription, translation

Replicate this strand of DNA
ATT ATT CGT GTA
Agenda for Tuesday May 10th
1. Transcription: Making RNA
2. Translation
DNA Info
• DNA never ever leaves the nucleus
– DNA is the master copy of the directions a cell
needs to live so it needs to be protected
DNA in the
nucleus is
safe
But DNA in the
cytoplasm can
be destroyed
RNA
• RNA is a copy of DNA that goes out into the
cytoplasm to tell the cell what to do in order
to stay alive
– RNA: ribonucleic acid
• RNA is similar to DNA
– Sugar is ribose not deoxyribose
– Nitrogen Base thymine is replaced with Uracil
– Single stranded
RNA
How many
strands?
DNA
RNA
2
1
Nucleotide
subunit
Phosphate
Group
Bases
Thymine (T)
Adenine (A)
Guanine (G)
Cytosine (C)
Nitrogen
Deoxyribose
Sugar
Base
T–A
G–C
Phosphate
Group
Uracil (U)
Adenine (A)
Guanine (G)
Cytosine (C)
Ribose
Sugar
Nitrogen
Base
U–A
G–C
3 types of RNA
• Messenger RNA (mRNA) – complementary to DNA
– C=G, A=U
– Travel from nucleus to ribosome
– Direct synthesis of protein
• Ribosomal RNA (rRNA) – associates with proteins to
form ribosomes
• Transfer RNA (tRNA) – transport amino acids to
ribosome
Transcription
• RNA is made from 1 strand of DNA
– Specifically mRNA (messenger RNA) because it
sends a message from DNA to the cytoplasm
DNA safe in
the nucleus
Uses mRNA
To send a
message to
the cytoplasm
Transcription
1. Unzip DNA
2. RNA Polymerase binds to synthesize RNA
3. Match up bases to one strand of DNA in the
5’ to 3’ direction (adds to 3’ end)
1. Use Uracil instead of thymine
4. mRNA detaches from the DNA
5. mRNA moves out of the nucleus and into the
cytoplasm
DNA
mRNA
mRNA
Cytoplasm of
cell
Nucleus
Transcription
happens in the
nucleus. An RNA
copy of a gene is
made.
Then the mRNA that
has been made moves
out of the nucleus
into the cytoplasm
Once in the
cytoplasm, the mRNA
is used to make a
protein
Transcribe your DNA
(get your paper from replicating DNA)
1. Does the mRNA model more closely resemble the
DNA strand from which it was transcribed or the
complementary strand that wasn’t used? Explain
2. Explain how the structure of DNA enables the
molecule to be easily transcribed. Whys is this
important for genetic information?
3. Whys is RNA important to the cell? How does an
mRNA molecule carry information from DNA?
4. If DNA strand read AAC GTC GCG TAC, what would
the mRNA strand be?
A little more about RNA
• RNA is shorter than DNA
• DNA is interrupted by short sequences that are
not in the final mRNA
– These are called introns
– Sequences that are kept in the final mRNA sequence
are called exons
Translation
The Code
• 20 amino acids (AA) used to make proteins
– DNA provides at least 20 different codes
• If each base coded for an AA then we could
only get 4 AA
• If a pair of bases coded for an AA then we
could get 16 (4x4)
• If 3 bases coded for an AA then we could get
64 (4x4x4)
The Code
• We find that every 3 bases codes for an amino
acid sequence
– Some amino acids are repeated
• Three base code is called a codon
– All but 3 codons code for an amino acid
• A chart was made to show each AA that
DNA/mRNA codes for
Translation
• mRNA is synthesized and moves to the ribosomes
– Located on the Rough ER
• mRNA then attaches to the ribosome
• tRNA interprets the mRNA codon sequence and
brings the appropriate amino acid
– Several amino acids make proteins
– Continues until a stop codon is reached (3)
tRNA
• 3 base sequence at the bottom – anticodon
– Matches the codon on the mRNA strand
Ribosome
• 2 subunits – only together during translation
– Attach the to mRNA strand
– 3 grooves, E site, P site, and A site
• Each groove holds a tRNA
– E site – exit
– P site – add amino acid to polypeptide chain
– A site – new tRNA arrives
Translate your DNA
Questions
1. Write your Amino Acid Sequence
2. Would you make a complete protein?
Explain.
3. Transcribe and translate the following DNA
sequence. Draw a line separating each
codon:
A T C G T C C A A
Transcribe (make RNA) and translate
(make amino acids/proteins) from this
strand of DNA
AAA TGC ACG TCG
Agenda for Wednesday May 11th
1. Review Replication, transcription, and
translation
2. Practice
Replication
• DNA Helicase unzips DNA
– Proteins bind to keep it apart
• Primers bind to DNA strands
• DNA Polymerase adds nucleotides to DNA
– Leading – continuous adding of bases
– Lagging – Okazaki fragments
• DNA Ligase fills in gaps
Transcription
• DNA Helicase unzips DNA
• RNA Polymerase adds bases to the template
strand of DNA
– Only 1 strand of DNA gets copied
• RNA detaches from DNA strand
• RNA moves into cytoplasm
Translation
• mRNA attaches to ribosomes
• tRNA moves into ribosome
• Anticodon matches with mRNA strand and
adds an amino acid
– tRNA leaves ribosome
• Stop codon is reached & amino acid chain
(polypeptide) detaches from ribosome
– Folds and creates a protein
DNA vs. RNA
DNA
RNA
2 Strands
1 Strand
Deoxyribose sugar
Ribose Sugar
A-T
C-G
A-U
C-G
How is RNA different from DNA
Agenda for Thursday May 12th
1. Practice with transcription and translation
2. Regulations and Mutations
Which RNA gets translated (mRNA,
tRNA, rRNA)?
Agenda for Monday Nov 8th
1. Replication, transcription, translation (one
last time)
1. Questions 2 and 3 on page 335
2. Questions 1 – 4 on page 341
2. Practice
3. Gene Regulation