The structure of DNA allows efficient storage of genetic information.
2.6 Structure of DNA and RNA
Essential idea:
| Statement | Guidance |
2.6.U1 | The nucleic acids DNA and RNA are polymers of nucleotides. | |
2.6.U2 | DNA differs from RNA in the number of strands present, the base composition and the type of pentose. | |
2.6.U3 | DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs. | |
2.6.A1 | Crick and Watson’s elucidation of the structure of DNA using model making. | |
2.6.S1 | Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases. | In diagrams of DNA structure, the helical shape does not need to be shown, but the two strands should be shown antiparallel. Adenine should be shown paired with thymine and guanine with cytosine, but the relative lengths of the purine and pyrimidine bases do not need to be recalled, nor the numbers of hydrogen bonds between the base pairs. |
2.6 Structure of DNA and RNA
Syllabus Reference
2.6 Structure of DNA and RNA
Vocabulary
Let’s introduce DNA!
Challenge: What does DNA stand for?
(deoxyribonucleic acid)
What does RNA stand for?
(ribonucleic acid)
2.6 Structure of DNA and RNA
What is DNA?
Do Now
2.6 Structure of DNA and RNA
What is the structure of a nucleotide?
2.6.U1 The nucleic acids DNA and RNA are polymers of nucleotides.
Phosphate Group
Nitrogenous Base
A, U, C, G
Ribose
1
2
3
4
5
2.6 Structure of DNA and RNA
2.6.U1 The nucleic acids DNA and RNA are polymers of nucleotides.
Phosphate Group
Nitrogenous Base
A, T, C, G
Deoxyribose
1
2
3
4
5
2.6 Structure of DNA and RNA
RNA contains one of four nitrogenous bases:
2.6 Structure of DNA and RNA
What is the structure of a nucleotide?
2.6.U1 The nucleic acids DNA and RNA are polymers of nucleotides.
DNA contains one of four nitrogenous bases
DNA Nucleotide Structure
2.6 Structure of DNA and RNA
What is the structure of a nucleotide?
2.6.U1The nucleic acids DNA and RNA are polymers of nucleotides.
Each sugar of the backbone is covalently bonded to the nitrogenous base off of carbon 1 of the ribose sugar.
carbon 1
2.6 Structure of DNA and RNA
Where is there a covalent bond?
This is known as an antiparallel strand of DNA
2.6 Structure of DNA and RNA
What is the structure of a nucleotide?
2.6.U3 DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.
3’
(3 Prime End)
5’
(5 Prime End)
Covalent bonds link carbon 3 and 5
Phosphodiester Bond
3’ (3 Prime End)
5’ (3 Prime End)
2.6 Structure of DNA and RNA
There are 10 base pairs per turn of the helix.
2.6.U3 DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.
2.6 Structure of DNA and RNA
How do we draw a molecule of DNA?
2.6.S1 Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases.
U C and T are single ringed pyrimidines
What do YOU see?
You See Trent at 1 pyramid
U C T at single pyramid
2.6 Structure of DNA and RNA
What are the 4 bases?
2.6.U1The nucleic acids DNA and RNA are polymers of nucleotides.
What are the 4 bases in DNA?
The nucleotides are similar, but:
(Uracil, U) C and T are single ringed pyrimidines
A and G are double ringed purines.
G and C share 3 hydrogen bonds
2.6 Structure of DNA and RNA
What are the 4 bases?
2.6.U1The nucleic acids DNA and RNA are polymers of nucleotides.
2) The amount of A = T, and the amount of C = G.
2.6 Structure of DNA and RNA
How many A’s T’s C’s and G’s?
2.6.U3 DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.
Edwin Chargaff, in 1949, noted two critical bits of data.
1) The four kinds of nucleotide bases making up a DNA molecule differ in relative amounts from species to species
2.6 Structure of DNA and RNA
What is the structure of a nucleotide?
2.6.U3 DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs.
What is complementary base pairing?
2.6 Structure of DNA and RNA
What is complementary base pairing?
Do Now
A little bit of DNA History
2.6 Structure of DNA and RNA
2.6.A1 Crick and Watson’s elucidation of the structure of DNA using model making.
Rosalind Franklin used x-ray diffraction techniques to produce images of DNA molecules.
2.6 Structure of DNA and RNA
What did Rosalind Franklin do?
2.6.A1 Crick and Watson’s elucidation of the structure of DNA using model making.
She concluded:
molecule of uniform diameter
2.6 Structure of DNA and RNA
What did Rosalind Franklin do?
2.6.A1 Crick and Watson’s elucidation of the structure of DNA using model making.
2.6 Structure of DNA and RNA
Francis Crick and James Watson and the first correct model of DNA
2.6.A1 Crick and Watson’s elucidation of the structure of DNA using model making.
Watson and Crick gained Nobel prizes for their discovery. It should be remembered that their success was based on the evidence they gained from the work of others.
In particular the work of Rosalind Franklin and Maurice Wilkins, who were using X-ray diffraction was critical to their success.
Franklin’s Story
2.6 Structure of DNA and RNA
Who was Rosalind Franklin?
2.6.A1 Crick and Watson’s elucidation of the structure of DNA using model making.
Watson and Crick used numerous sources of data to build models of DNA.
2.6 Structure of DNA and RNA
What is the story?
2.6.A1 Crick and Watson’s elucidation of the structure of DNA using model making.
Watch this!
2.6 Structure of DNA and RNA
How do we draw a molecule of DNA?
2.6.S1 Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases.
Build a DNA Molecule
2.6 Structure of DNA and RNA
Put DNA together
2.6.S1 Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases.
Deoxyribose versus Ribose
Deoxy - minus one oxygen atom
2.6 Structure of DNA and RNA
Both contain 5 carbon (pentose) sugars
2.6.U2 DNA differs from RNA in the number of strands present, the base composition and the type of pentose.
DNA | RNA |
Double stranded | Single stranded |
A, C, G and T | A, C, G and U Uracil replaces thymine |
Deoxyribose | Ribose |
Found only in nucleus | Found in nucleus and cytoplasm |
n/a | Several forms - mRNA, tRNA, rRNA |
2.6 Structure of DNA and RNA
What is the difference between DNA and RNA
2.6.U2 DNA differs from RNA in the number of strands present, the base composition and the type of pentose.
The Discovery of DNA (& other stuff)
2.6 Structure of DNA and RNA
2.6.A1 Crick and Watson’s elucidation of the structure of DNA using model making.
Hershey and Chase confirmed that DNA is the hereditary material
(not protein).
2.6 Structure of DNA and RNA
2.6.A1 Crick and Watson’s elucidation of the structure of DNA using model making.
A. phosphate, deoxyribose and nitrogenous base
B. phosphorus, ribose and nitrogenous base
C. phosphorus, deoxyribose and guanosine
D. phosphate, ribose and guanine
2.6 Structure of DNA and RNA
1.Which molecules form the nucleotide marked in the diagram?
Plenary
2. Which of the following are connected by hydrogen bonds?
A. Hydrogen to oxygen within a molecule of water
B. Phosphate to sugar in a DNA molecule
C. Base to sugar in a DNA molecule
D. Hydrogen to oxygen between two different molecules of water
2.6 Structure of DNA and RNA
Plenary
3. The percentage of thymine in the DNA of an organism is approximately 30%. What is the percentage of guanine?
A. 70%
B. 30%
C. 40%
D. 20%
2.6 Structure of DNA and RNA
4.Which base is connected to its complementary base in a base pair by three hydrogen bonds?
A. Uracil
B. Thymine
C. Guanine
D. Adenine
2.6 Structure of DNA and RNA
1.Which molecules form the nucleotide marked in the diagram?
5. Which molecule is found in both DNA and RNA?
A. Ribose
B. Uracil
C. Phosphate
D. Amino acid
2.6 Structure of DNA and RNA
6. The following diagram shows a short stretch of DNA. What bases are indicated by labels Y and Z?
2.6 Structure of DNA and RNA
7.Draw a labelled diagram to show how two nucleotides are joined together in a single strand of DNA (3)
2.6 Structure of DNA and RNA
Answers
7.
2.6 Structure of DNA and RNA
Extract some DNA!
2.6 Structure of DNA and RNA
Extracting DNA
Extract some DNA!
2.6 Structure of DNA and RNA
2.6 Structure of DNA and RNA