1. STRUCTURE OF DNA
TOPIC

2. YEAR 10 BIOLOGY Topics Structure of DNA Chromosomes & Cell division
Genetics & Inheritance
Theory of Evolution
Evidence for Evolution

3. YEAR 10 BIOLOGY Assessment
Evolution poster
Genetics prac report
Unit test
End of semester examination
and various worksheets
/ quizzes throughout the
course...

4. STRUCTURE OF DNA Things to cover
History
Location
Components
Base pairing
Shape

5. HISTORY OF DNA

6. HISTORY OF DNA 1869 DNA was discovered by Friedrich Miescher
His team isolated it from pus on bandages!
He called their discovery nuclein.

7. HISTORY OF DNA 1929
Phoebus Levene determined that the compound had a repeating structure.
He called these repeated units nucleotides.
He also suggested that these units link together to form chains.
His theory was correct, but his prediction about the way the chains formed was not.

8. HISTORY OF DNA
Oswald Avery , and Alfred Hershey and Martha Chase made the suggestion that this compound was capable of transferring genetic information between generations

9. HISTORY OF DNA 1950
Erwin Chargaff determined that there were four types of nucleotides that paired up within the structure of DNA
This is known as Chargaff’s rule or the base pairing rule.

10. HISTORY OF DNA 1953
Rosalind Franklin came very close to solving the DNA structure
She made xray crystallographic portraits of DNA in order to try to determine its 3D structure.
Source:

11. HISTORY OF DNA 1953
Her work was given without her consent to a group of scientists in another laboratory by her colleague, Maurice Wilkins.
Source:

12. HISTORY OF DNA 1953
James Watson and Francis Crick made a model of DNA that incorporated the findings of Chargaff, Franklin and Wilkins.
Their model fit the experiential data so perfectly that it was almost immediately accepted.
Source: tokresource.org

13. HISTORY OF DNA 1962
JOHN STEINBECK
WILKINS
CRICK
WATSON
Watson, Crick, and Wilkins won the Nobel Prize for physiology/ medicine.
Rosalind Franklin had died of cancer in 1956.
Source: achievement.org

14. HISTORY OF DNA 1962
The Nobel Prize only goes to living recipients, and can only be shared among three winners.
Were she alive, do you think she would have been included in the prize?
Source: omniscienceblog.com

16. LOCATION OF DNA

17. LOCATION OF DNA
DNA is a chemical located in the nucleus of every living cell.
NUCLEUS
DNA

18. LOCATION OF DNA It is a nucleic acid.
Its full name is deoxyribonucleic acid.
Its role is to store coded instructions about how to make proteins.
In this way, it directs cell division, growth & function.

19. COMPONENTS OF DNA

20. COMPONENTS OF DNA
DNA is a large molecule made up of smaller sub-units called nucleotides
Each nucleotide consists of:
a nitrogenous base
a pentose sugar
a phosphate group
There are four different DNA nucleotides

21. COMPONENTS OF DNA Pentose sugars
There are two sugars that are used in nucleotides:
deoxyribose sugar  used in DNA
ribose sugar  used in RNA

22. COMPONENTS OF DNA Nitrogen bases
There are four nitrogen bases in DNA:
A = Adenine
T = Thymine
G = Guanine
C = Cytosine
There is a fifth nitrogen base found only in RNA:
U = Uracil

23. COMPONENTS OF DNA Chemical bonds
The three components are held together by covalent bonds.
These bonds are strong so that the unit holds together within the larger molecule.
COVALENT BOND
COVALENT BOND

24. CHARGAFF’S BASE PAIRING RULE

25. BASE PAIRING IN DNA C G A T
The nitrogen bases exhibit complementary base pairing.
This means that each base only join with one other base:
Adenine joins with Thymine (A=T)
Guanine joins with Cytosine (C≡G) C G A T

26. BASE PAIRING IN DNA Reasons behind the rule: Size of bases
Number of hydrogen bonding sites

27. SHAPE OF DNA

28. SHAPE OF DNA DNA is double stranded.
Each strand is made up of nucleotides, connected through chemical bonds.
These two strands are twisted around each other.
This is called a double helix.

29. SHAPE OF DNA The structure is similar to a twisted ladder.
The “rungs” of the ladder are made from the complementary nitrogen base pairs.
The “sides” of the ladder are made from alternating sugar and phosphate groups.
This is called the sugar-phosphate backbone.

30. C G A T COMPLEMENTARY NITROGEN BASE PAIRS SUGAR-PHOSPHATE BACKBONE

31. SHAPE OF DNA
The nucleotides are joined by covalent bonds  these are very strong
The two strands are joined by hydrogen bonds  these are very weak,
This allows the strands to be separated during DNA replication and protein synthesis without destroying the DNA completely

32. COVALENTBONDS
HYDROGEN BONDS C G A T