Transcript IB Topics DNA HL no writing

IB Topics: DNA,
Transcription, Translation
(3.3, 3.4, 3.5)
7.1, 7.2, 7.3, 7.4
7.1
DNA Structure
7.1.1 Describe the structure of DNA, including the
7.1.2 Outline the structure of
nucleosomes.
7.1.3 State that nucleosomes help to supercoil
chromosomes and help to regulate transcription.
7.1.4 Distinguish between unique or singlecopy genes & highly repetitive sequences in
nuclear DNA.
7.1.5 State that eukaryotic genes can contain
exons and introns.
Happy Tuesday!! 8/28
Living organisms use DNA as their genetic
material. Explain how DNA is replicated within the
cells of living organisms.
(Total 8 marks)
• helix is unwound;
• two strands are separated;
• helicase (is the enzyme that unwinds the helix separating the
two strands);
• by breaking hydrogen bonds between bases;
• new strands formed on each of the two single strands;
• nucleotides added to form new strands;
• complementary base pairing;
• A to T and G to C;
• DNA polymerase forms the new complementary strands;
• replication is semi-conservative;
• each of the DNA molecules formed has one old and one new
strand;
• [8]
7.2
DNA Replication
7.2.1 State that DNA replication occurs in a 5  3
direction.
7.2.2 Explain the process of DNA replication in prokaryotes, including
the role of enzymes
7.2.2 Explain the process of DNA replication in prokaryotes, including
the role of enzymes
IB Book, fig 7.7 page 200
• Examiner’s Hint
– Draw the figure from memory
– Annotate what’s happening at specific
locations
7.2.3 State that DNA replication is initiated at
many points in eukaryotic chromosomes.
Primer
Primer
LIFE book
Sure Happy It’s Thursday, 8/30
• Explain the process of transcription in
eukaryotes.
• (8)
• RNA polymerase controls transcription / is the enzyme used in
transcription;
• DNA is unwound by RNA polymerase;
• DNA is split into two strands;
• mRNA is made by transcription;
• promoter region (by start of gene) causes RNA polymerase to bind;
• anti-sense / template strand of DNA is transcribed;
• direction of transcription is ;
• free nucleotide triphosphates used;
• complementary base pairing between template strand and RNA
nucleotides / bases;
• Accept this marking point if illustrated using a diagram
• RNA contains uracil instead of thymine;
• terminator (sequence) stops RNA polymerase / transcription;
• mRNA is released / RNA polymerase released;
8 max
• List three of the other molecules, apart from
mRNA, required for transcription.
• 3 mks
• DNA;
• RNA polymerase;
• (ribose) nucleotides / ribonucleotides / RNA
nucleotides;
• transcription factors;
• nucleoside / ribonucleoside triphosphates;
3 max
• Any two of the following: A / C / G / U;
7.3
Transcription
7.3.1 State that transcription is
carried out in a 5  3 direction.
7.3.2 Distinguish between the
sense & antisense strands of
DNA.
7.3.3 Explain the process of transcription in prokaryotes, including the
role of the promoter region, RNA polymerase, nucleoside triphosphates
terminator.
7.3.4 State that eukaryotic RNA needs the removal
of introns to form mature mRNA.
THURSDAY, 9/2
• The information needed to
make polypeptides is carried in
the mRNA from the nucleus to
the ribosomes of eukaryotic
cells. This information is
decoded during translation. The
diagram below represents the
process of translation.
• State the name of the next
amino acid which will attach to
the polypeptide. (1)
• Explain how the amino acid was
attached to the tRNA. (3)
• Alanine / Ala 1
• an activating enzyme attaches amino acid to
the tRNA;
• specific enzyme for specific tRNA;
• recognizes tRNA by its shape / chemical
properties;
• energy (ATP) is needed;
• amino acid attached at end;
• amino acid attached at CCA; 3 max
Happy Thursday! 9/2/2010
Explain the process of translation.
• (Total 9 marks)
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consists of initiation, elongation and termination;
mRNA translated in a 5' to 3' direction;
binding of ribosome to mRNA;
small sub-unit then large;
first / initiator tRNA binds to start codon / to small subunit of ribosome;
AUG is the start codon;
second tRNA binds to ribosome;
large subunit moves down mRNA after a second tRNA binds;
amino acid / polypeptide on first tRNA is transferred / bonded to amino acid
on second tRNA;
peptide bonds between amino acids / peptidyl transferase;
requires GTP;
movement of ribosome / small subunit of ribosome down the mRNA;
loss of tRNA and new tRNA binds;
reach a stop codon / termination;
polypeptide released;
tRNA activating enzymes link correct amino acid to each tRNA;
(activated) tRNA has an anticodon and the corresponding amino acid
attached;
[9]
7.4
Translation
7.4.1 Explain that each tRNA molecule is recognized by a
tRNA-activating enzyme that binds a specific amino acid to
the tRNA, using ATP for energy.
7.4.2 Outline the structure of ribosomes,
including protein and RNA composition, large
and small subunits, three tRNA binding sites,
mRNA binding sites.
7.4.3 State that translation consists of initiation,
elongation, translocation, termination.
7.4.3 State that translation consists of initiation,
elongation, translocation, termination.
7.4.3 State that translation consists of initiation,
elongation, translocation, termination.
7.4.3 State that translation consists of initiation,
elongation, translocation, termination.
7.4.4 State that translation occurs in a 5  3
direction.
7.4.5 Draw and label the structure of a peptide
bond between two amino acids.
7.4.6 Explain the process of translation, including
ribosomes, polysomes, start codons and stop codons.
7.4.7 State that free ribosomes synthesize
proteins for use primarily within the cell, and that
bound ribosomes synthesize proteins primarily for
secretion or for lysosomes.