B8: Nucleic acids
B.8.1  Describe the structure of nucleotides and their condensation polymers
(nucleic acids or polynucleotides).
[Nucleic acids are polymers made up of nucleotides. A nucleotide contains a phosphate
group, a pentose sugar and an organic nitrogenous base. Students should recognize,
but do not need to recall, the structures of the five bases: adenine(A), cytosine(C),
guanine(G), thymine(T) and uracil (U). Nucleic acids are joined by covalent bonds
between the phosphate of one nucleotide and the sugar of the next, resulting in a
backbone with a repeating pattern of sugar-phosphate-sugar-phospate. Nitrogenous
bases are attached to the sugar of the backbone.]
Nucleic acids = polymers made up of __________________
Examples:
 __________________________ acid (DNA)
 ___________________________acid (RNA)
*More on the complete structures of DNA and RNA later.
A. Nucleotides
Nucleotides consist of:
1. a _________
group:
2. a
sugar:
*DNA contains  _______________
*RNA contains  ______________
3. an organic
:
*DNA contains adenine(A), cytosine(C), guanine(G),and thymine(T)
*RNA contains  adenine(A), cytosine(C), guanine(G), and uracil (U]
DNA bonding base pairs
*Uracil replaces thymine in RNA
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Examples of Complete Nucleotides:
B. Polynucleotides
Nucleotides condense to form ____________________. Each nucleotide is joined by a
_______________________ bond between C3 of the ________________ and the
neighbouring __________________ group.
or
C. Nucleic acids  DNA and RNA
B.8.3  Explain the double helical structure of DNA.
[The structure has two nucleic acid strands that spiral around an axis. Students should describe the
hydrogen bonding between specific pairs of nucleotide bases.
TOK: What are the implications of the discovery of the molecular basis of life in other areas of
knowledge?]
RNA
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B.8.2  Distinguish between the structures of DNA and RNA.
[RNA has ribose as its pentose sugar; DNA has deoxyribose. Deoxyribose lacks an
oxygen atom on C2. RNA has uracil instead of thymine as its base. RNA is a singlestand nucleic acid; DNA is a double-strand nucleic acid.]
Summary:
DNA
RNA
Pentose sugar
Bases
# of nucleic acid
strands
B.8.4  Describe the role of DNA as the repository of genetic information, and explain
its role in protein synthesis.
[DNA is the genetic material that an individual inherits from its parents. It directs
mRNA synthesis (transcription) and, through mRNA, directs protein synthesis
(translation) using a triplet code.]
Protein Synthesis (Steps)
1. ____________________ = synthesis of _________ (i.e. messenger RNA) via
“unzipping” of ________
 mRNA base sequence is ___________________ to that on a section of DNA
e.g. DNA base seqenence
 A G G C T C G A G G T T
Complementary mRNA strand 
 Transcription takes place in the ______________of the cell.
 Upon completion of transcription, the mRNA travels into the
___________ of the cell.
2. _________________= synthesis of _______________chain via the
“decoding” of base sequences on the mRNA strand
 Each ____________ base sequence (i.e. each _________ code) on
the mRNA codes for an ______________ acid.
 There are ____ (i.e. 44) possible triplet codes and only ___ amino
acids. Therefore, most amino acids are represented by more than one
triplet code. (e.g. GCU, GCC, GCA, GCG all code for alanine.)
Some sequences code for start and end of the chain.
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8.8.5  Outline the steps involved in DNA profiling and state its use.
[Aim 8: Include forensic and paternity cases.]
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