1. Rosalind Franklin suggested that DNA has a spiral shape. 2. James Watson and Francis Crick presented the DNA model in 1953 at Cambridge University and were later awarded the Nobel Prize for this work. 3. The document goes on to provide more details about the structure of DNA, including that it is a double helix with deoxyribose and phosphate as the backbone and adenine, thymine, guanine, and cytosine as the nitrogen bases that form base pairs between the two strands.

1. Warm up
A. Who suggested that DNA has spiral shape.
B. Who presented the DNA model in 1953 at Cambridge
University, London. The Nobel Prize was awarded for presenting
this DNA model.
Rosalind Franklin James Watson and Francis Crick

2. DNA STRUCTURE (REVIEW)
By Mrs Kasturey
and Mrs Rose

3. Complete DNA-R-US
worksheet as we go
through PPT
3

4. A double-stranded nucleic acid that
contains the genetic information for cell
growth, division, and function
4
DNA
Deoxyribonucleic Acid
1. DNA stands for
___________________________ _________
and is the basic substance of heredity.

5. DNA is a set of _____________ for
building your body and controls
everything about the way you
____ and __________.
What is DNA?
DNA is a set of
instructions for building
your body and controls
everything about the
way you look and
function.

6. Double-helix
3. A DNA _________ looks like a twisted
ladder. Because of its shape, a DNA
molecule is often called a “_______
________”. A helix is shape that twist.
 A DNA _molecule_ looks like a twisted
ladder. Because of its shape, a DNA
molecule is often called a “_double_
_helix_”. A helix is shape that twist.

7. 4. The DNA double helix looks like a twisted ladder.
The side of the ladder, the hand railing, are made
of ___________________ and _____________.
 The DNA double helix looks
like a twisted ladder. The
side of the ladder, the hand
railing, are made of _sugar
molecule and
_phosphate_.
Side railings

8. 5. The rungs of the ladder are formed by pairs of
___________________________.
The rungs of the
ladder are formed
by pairs of
__Nitrogen bases.

9. Nitrogen Bases
6. Nitrogen bases are molecules that contain the
element ______________ and other element.
 Nitrogen bases
are molecules
that contain the
element
__Nitrogen and
other element.

10. 7. The two sides of DNA ladder are made up of
molecules of a sugar called
__________________, alternating with the
molecules known as ________________.
 The two sides of DNA ladder are made up of
molecules of a sugar called _deoxyribose_,
alternating with the molecules known as
_phosphates.
Back bone

11. 8. There are four types of nitrogen bases:
a. (ad uh neen) ________________.
b. (thy meen) _________________.
c. (gwah neen) ________________.
d. (sy tuh seen) ________________.
 There are four types of
nitrogen bases:
a. (ad uh neen)
________________.
b. (thy meen)
_________________.
c. (gwah neen)
________________.
d. (sy tuh seen)
________________.
11

12. 9. Adenine always pair with ________________;
and Guanine always pair with ______________.
 Adenine always
pair with
_Thymine; and
Guanine always
pair with
_Cytosine.
Base pair pairing

13. DNA-R-Us
DNA DNA
guanine G Cytosine
Thymin-T Adenine
adenine A Thymin
cytosine C Guanine

14. 10. The pairing pattern is the key to
understanding how DNA _________ occurs.
 The pairing pattern is the
key to understanding
how DNA _replication_
occurs.
Replication

15. 11. So if one side of DNA
ladder has –
Then the other side will be –

16. Making the complete
structure –
 OR in simple letters – C A A G
 G T T C
16

17. Now your turn to try –
Simply write the matching
base pair.
NO NEED TO DRAW the other
side.
Practice