Happy Homecoming Friday!!!
1. Which of the following is required for osmosis to occur?
A. An enzyme
B. A fully permeable membrane
C. ATP
D. A solute concentration gradient
2. Which of the following processes take place during interphase?
I. Respiration
II. Active transport
III.Protein synthesis
IV.Replication of DNA
A. I only
B. I and II only
C. I, II and III only
D. I, II, III and IV
Pelican Book 1st
• Then IB book 3.3
• THEN go over diffusion/osmosis lab
• Test Corrections due when?!?!
IB Topics: DNA,
Transcription, Translation
3.3, 3.4, 3.5
http://simplescience.net/dna.html
3.3
DNA Structure
3.3.1 Outline DNA nucleotide structure in terms of
sugar (deoxyribose), base and phosphate.
• Chemical formulas not required! 
• Simple shapes!
• Bases:
–
–
–
–
A
T
G
C
• Carbon #s
3.3.2 State the names of the four bases in DNA.
PYRIMIDINES
3.3.3 Outline how DNA nucleotides are linked
together by covalent bonds into a single strand.
• Phosphodiester bond = cov
• 5’ P group + 3’ OH group
• Condensation rxn—water
Released
Nucleotides added to 3’ end!
Sugar-phosphate backbone
3.3.4 Explain how a DNA double helix is formed
using complementary base pairing and hydrogen
bonds.
• A-T; G-C
– A, G are purines—bigger
– T, C are pyrimidines—smaller
• Consistent width of dbl helix
• Opposite directions (anti-parallel)
3.3.5 Draw and label a simple diagram of the
molecular structure of DNA
TOK:
story of elucidation of DNA
structure
(collaboration; Watson and
Crick’s discovery of 3D
structure dependent on
Franklin’s data…shared
without her knowledge or
consent!!!)
3.4
DNA Replication
3.4.1 Explain DNA replication in terms of unwinding the double helix
and separation of the strands by helicase, followed by formation of the
new complementary strands by DNA polymerase.
• Interphase, before cell division
– Chromatin
• Helicase (100s of base pairs per sec!)
– Moves base pair at a time, breaks H bonds
– Each strand is now a template
• DNA polymerases
– Covalent bonds b/w new strand n’tides
– Free nucleotides (nucleoside
triphosphates)
3.4.2 Explain the significance of complementary
base pairing in the conservation of the base
sequence of DNA.
• Double stranded, complementary
• Each becomes a template
• Complementary  Identical daughter
strands
• Accuracy for passing on information
– Gene expression
– Fatal mistakes
3.4.3 State that DNA replication is semiconservative.
• Neither is completely “new”
– (Semi-conservative)
• Meselson & Stahl expts
• Heavy & light isotopes of N
3.5
Transcription & Translation
3.5.1 Compare the structure of RNA and DNA.
**similarities & differences!! 5 are listed (not 10!):
DNA
RNA
5-C sugar
5-C sugar
Deoxyribose sugar
Ribose sugar
Each nucleotide has 1 of
4 nitrogenous bases
Bases are C, G, A, T
Each nucleotide has 1 of
4 nitrogenous bases
Bases are C, G, A, U
Double-stranded
Single-stranded
Why’s the nucleus called the
“control center”?
• Protein synthesis
• Some are enzymes
• Effects biochemistry of cell...carbs,
lipids, etc.
3.5.2 Outline DNA transcription in terms of the formation
of an RNA strand complementary to the DNA strand by
RNA polymerase.
• Gene region on DNA is unzipped
• RNA polymerase moves along template DNA
strand (1) & complementary RNA n’tides pair
• U instead of T
• Compl copy of ONE GENE of the
chromosome
3.5.3 Describe the genetic code in terms of codons
composed of triplets of bases.
•
•
•
•
3 mRNA bases
Codes for ONE amino acid
“codon”
Sequence for polypeptide
Happy THURSDAY!!! March 4th!
Test Monday, Articles & Review Tomorrow!
1. During the process of translation which of the following statements
describes the relationship between nucleic acids?
A.
Anticodons on mRNA bind to complementary codons on DNA.
B.
Anticodons on tRNA bind to complementary codons on mRNA.
C.
Bases on DNA bind to complementary bases on mRNA.
D.
A single strand of mRNA is produced from the DNA in the nucleus.
2. Define the term degenerate as it relates to the genetic code. (1 mark)
more than one codon / base triplet codes for an amino acid 1
Translation
3.5.4 Explain the process of translation, leading to
polypeptide formation.
• Include the roles of messenger RNA
(mRNA), transfer RNA (tRNA), codons,
anticodons, ribosomes and amino
acids.
RNA
• mRNA:
– complementary copy of a gene, codes for one
polypeptide
• rRNA:
– ribosomal (ribosome = rRNA + ribosomal protein)
• tRNA:
– transfers ONE of the 20 AA to ribosome for
polypeptide formation
– anticodon complementary to codon, determines
which AA attaches to tRNA
3.5.4 Explain the process of translation, leading to
polypeptide formation.
• mRNA leaves through
nuclear pore, goes to
ribosome @ 1st 2 codons
3.5.4 Explain the process of translation, leading to
polypeptide formation.
• tRNA anticodons match up,
bring amino acids in
sequence
3.5.4 Explain the process of translation, leading to
polypeptide formation.
• 2nd tRNA brings next one,
condensation rxn  cov
bond creates peptide bond
3.5.4 Explain the process of translation, leading to
polypeptide formation.
• tRNA breaks bond w/amino acid, floats
away & reloads
• Ribosome moves down mRNA, ...until
stop codon: all dissociate
http://learn.genetics.utah.edu/content/begin/dna/firefly/
3.5.5 Discuss the relationship between one gene
and one polypeptide.
• Originally (1940s) 1 gene  1 enzyme
•  all proteins
•  many proteins are multiple polypeptides,
each translated by a separate gene
• would invariably code for one polypeptide,
but many exceptions have been discovered.
• ACTUALLY...one mRNA can be modified in
different ways to produce different
polypeptides...
•
TOK: The way in which theories are modified as related evidence
accumulates could be discussed, and whether contrary evidence
should cause a theory to be discarded immediately if there are
exceptions to it. Where a theory is suddenly and totally abandoned, to
be replaced by a different theory, this is known as a paradigm shift.