1. 1
DNA
The illustration is a ‘model’ of the double helix forming part of a DNA molecule
(Slide 14)

2. DNA stands for deoxyribose nucleic acid2
DNA stands for deoxyribose nucleic acid
This chemical substance is present in the nucleus
of all cells in all living organisms
DNA controls all the chemical changes which
take place in cells
The kind of cell which is formed, (muscle, blood,
nerve etc) is controlled by DNA
The kind of organism which is produced (buttercup,
giraffe, herring, human etc) is controlled by DNA

3. DNA is a very large molecule made up of a long chain of sub-units
DNA molecule 3
DNA is a very large molecule made up of a long
chain of sub-units
The sub-units are called nucleotides
Each nucleotide is made up of
a sugar called deoxyribose
a phosphate group -PO4 and
an nitrogenous base (A, T, C, G)

4. Ribose is a sugar, like glucose, but with only five
Ribose & deoxyribose 4
Ribose is a sugar, like glucose, but with only five
carbon atoms in its molecule (found in RNA)
Deoxyribose is almost the same but lacks one
oxygen atom (found in DNA)
Both molecules may be represented by the symbol
Pentose (5-carbon) sugars. Always represented by pentagons

5. The most common organic bases are
The bases 5
The most common organic bases are
Adenine
(A)
Thymine
(T)
Cytosine
(C)
Guanine
(G)

6. This is a structure of a NUCLEOTIDE6
The deoxyribose,
the phosphate
and one of the bases
Combine to form a nucleotide
adenine
deoxyribose
PO4
It is the phosphate group which gives DNA its acidic properties
(Phosphate + sugar + nitrogen base) = nucleotide

7. Joined nucleotides 7
PO4
sugar-phosphate
backbone
+ bases
A molecule of DNA is formed by millions of nucleotides joined together in a long chain

8. Parts of a Nucleotide A, T, C, G
Phosphate + Pentose sugar Nitrogen Base
(deoxyribose)
(ribose)

9. In fact, the DNA usually consists of a double strand of nucleotides8
In fact, the DNA usually consists of a double
strand of nucleotides
The sugar-phosphate chains are on the outside
and the strands are held together by chemical
bonds between the bases

10. The bases always pair up in the same way
Bonding 1 10
The bases always pair up in the same way
Adenine forms a bond with Thymine
Adenine
Thymine
and Cytosine bonds with Guanine
Cytosine
Guanine

11. 2-stranded DNA 9 sugar Phosphate
PO4
PO4
Covalent bonds found b/t sugars and phosphates
PO4
PO4
Hydrogen bond found between Nitrogen bases
PO4
PO4
sugar
PO4
Nitrogen base
PO4
PO4
Phosphate

12. 14
THE DOUBLE HELIX
bases
sugar-phosphate
chain

13. On my webpage, there are questions for you to answer in your notes13
The paired strands are coiled into a spiral called
A DOUBLE HELIX
The term “Double Helix” was coined by two British Scientists named James Watson and Francis Crick in the 1950s...but should they have received the Nobel Prize??
If you haven’t already done so. Do a quick search and read about Watson & Crick and Rosalind Franklin.
On my webpage, there are questions for you to answer in your notes

14. A DIY model of part of a DNA molecule can be found at Wal-Mart15
A DIY model of part of a DNA molecule can be found at Wal-Mart
This is a teaching model. The colours of the bases do not conform to the accepted
scheme today

15. 1. Before a cell divides, the DNA strands unwind and separate
DNA replication 16
1. Before a cell divides, the DNA strands unwind
and separate
2. Each strand makes a new partner by adding
the appropriate nucleotides
3. The result is that there are now two double-stranded DNA molecules in the nucleus
4. So that when the cell divides, each nucleus
contains identical DNA
5. This process is called replication

16. 1. The strands separate 17
PO4
PO4
During DNA replication, the weak hydrogen bonds between the bases break—and the DNA unzips

17. Two new strands of DNA have been copied18
2-4. Each strand builds up its partner by adding the appropriate nucleotides
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
The nucleotides are present in the nucleoplasm. The nuclear equivalent of cytoplasm
PO4
PO4
PO4
PO4
PO4
Two new strands of DNA have been copied

18. RNA (ribonucleic acid)

19. Ribonucleic Acid Single stranded form of DNA
Responsible for Protein synthesis (making proteins)
Travels to the ribosomes (since the DNA cannot leave the nucleus), and aids in protein synthesis
There are three types:
Messenger RNA (mRNA)-brings message from DNA
Ribosomal RNA (rRNA)- makes structure of ribosome
Transfer RNA (tRNA)-transfers the amino acid to the site of protein synthesis

20. DNA vs. RNA (please copy this table)
Number of Strands 2 1
Nitrogen Bases
A, T, C, G
A, U, C, G
Sugar
Deoxyribose
Ribose
Base Pairing
A=T
C=G
A=U
Job (function)
Genetic material, instructions for cell function
Protein synthesis, making proteins
Location
Nucleus
Travels through cytoplasm ribosomes

21. DNA to Proteins
Protein Synthesis

22. Instructions for making proteins
DNA inside of the nucleus gives instructions for protein synthesis.
The DNA cannot leave the nucleus, so the mRNA must travel to the ribosomes
The RNA helps the ribosomes to make proteins.

23. The sequence of bases in DNA forms the
Genetic code 1 19
The sequence of bases in DNA forms the
Genetic Code
A group of three bases (a triplet or codon) controls
the production of a particular amino acid in
the cytoplasm of the cell
The different amino acids and the order in which they are joined up determines the sort of protein being produced

24. RNA Base Pairing DNA & RNA share many similarities and differences.
One of the main differences in the base pairing.
There is no THYMINE in RNA…there is URACIL
So A = U
Example
DNA Strand AAT CGC CAT
RNA Strand UUA CGC GUA

25. Rules of Protein synthesis
1. You are given a DNA base strand
2. You must convert it to mRNA
3. Find the amino acid that codes for the mRNA (p. 292 in Blue textbook has an amino acid chart)
FYI-chains of amino acids make PROTEINS.
Example:
DNA base strand: AAA CAT
mRNA strand: UUU GUA
AMINO ACID: Phenylalanine Valine

26. The Central Dogma (Protein Synthesis)
DNA RNA Proteins
mRNA travesls through the cytoplasm to the ribosomes where proteins
DNA inside of the nucleus gives instructions for Protein synthesis
The chains of amino acids make proteins
RNA codon:
UUU
Amino Acid: Phenylalanine
DNA codon: AAA

27. Valine Alanine For example Codes for Codes for Coding 21 Cytosine
Adenine
Valine
Codes for
Thymine
Cytosine (C)
Alanine
Codes for
Guanine (G)
Adenine (A)

28. This is known as the triplet code22
This is known as the triplet code
Each triplet codes for a specific amino acid
CGA - CAA - CCA - CCA - GCT - GGG - GAG - CCA -
Ala
Val
Gly
Gly
Arg
Pro
Leu
Gly
The amino acids are joined together in the correct
sequence to make part of a protein
Although the DNA in the nucleus specifies the amino acids and their sequence, it is in the cytoplasm that the protein build-up takes place. The DNA of the nucleus makes a single strand of messenger RNA (ribo-nucleic acid) which leaves the nucleus and builds up the protein in the cytoplasm. The RNA code is complementary, but not identical, to the nuclear DNA. Text books usually give the coding for the RNA but in this presentation it is for the DNA itself
Ala
Val
Gly
Gly
Arg
Pro
Leu
Gly

29. The proteins build the cell structures
DNA and enzymes 23
The proteins build the cell structures
They also make enzymes (enzymes are proteins)
The DNA controls which enzymes are made and
the enzymes determine what reactions take place
The structures and reactions in the cell determine
what sort of a cell it is and what its function is
So DNA exerts its control through the enzymes

30. A sequence of triplets in the DNA molecule may
Genes 24
A sequence of triplets in the DNA molecule may
code for a complete protein
Such a sequence forms a gene
There may be a thousand or more bases in
one gene

31. Question 1 Which of the following are components of nucleotides?
(a) deoxyribose
(b) amino acids
(c) phosphate
(d) enzymes
(e) organic bases

32. Question 2 Which of the following represent a correct
pairing of bases?
(a) adenine with thymine
(b) adenine with guanine
(c) thymine with adenine
(d) guanine with cytosine
(e) thymine with thymine

33. Question 3 DNA molecules are formed from (a) organic bases
(b) amino acids
(c) deoxyribose
(d) nucleotides

34. Question 4 Which of the following are organic bases? (a) Valine
(b) Guanine
(c) Thymine
(d) Serine

35. Question 5 Replication of DNA occurs (a) During cell division
(b) before cell division
(c) at any time

36. Question 6 A nucleotide triplet codes for (a) a protein
(b) an amino acid
(c) an enzyme
(d) an organic base

37. Answer
CORRECT

38. Answer
INCORRECT