deoxyribonucleic acid dna. o.l lesson objectives at the end of this lesson you should be able to 1....
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DEOXYRIBONUCLEIC ACID
DNA
O.L Lesson Objectives
At the end of this lesson you should be able to 1. Outline the simple structure of DNA – 2
strands and A,T,C, G complement2.Distinguish between coding and non coding
structures3.Describe the triplet base code4.Outline the structure of RNA – refer to Uracil
and complement to DNA5.Know the function of mRNA6.Discuss the replication of DNA
What is DNA
Hereditary material
Carries and passes on genetic information
It is a nucleic acid
Made up of nucleotides
The DNA Double Helix
Two parallel strands
Each with a series of bases to the inside
The bases are directly opposite each other
The bases link each other in pairs
These links form the steps of the ladder
The DNA Double Helix
Parallel StrandParallel Strand
BaseBase
Hydrogen bond- link
The Bases
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
The Base Pair Rule
The bases can occur in any sequence along a strand of DNA
But the sequence must be complimentary to the sequence on the other strand
The Base Pair Rule
Adenine can only join to Thymine A T
Guanine can only join to Cytosine
G C
http://www.zerobio.com/drag_gr9/DNA/dna.htm
Building DNA
Building DNA
http://learn.genetics.utah.edu/units/basics/builddna/
Learning Check
What does DNA stand for?
Name the four bases in DNA
Which base complements Adenine?
Which base compliments Guanine?
Non Coding DNA
Only about 3% of DNA is composed of genes
97% of DNA is non coding DNA or junk DNA
Coding DNA
The parts of DNA that contain information to make RNA or protein
Coding DNA in genes are called exons
Non Coding DNA
Do not contain critical information for the production of protein
They are now thought to play a role in gene expression
Non coding DNA within genes is called introns
Learning Check
Label a gene and a piece of non coding DNA in the following picture
RNA
Ribonucleic Acid
Operates with DNA to make proteins
Has Uracil instead of Thymine
Differences between DNA and RNA
DNA
Double strand
Sugar is deoxyribose
Has Thymine
Very long
Self replicating
Found only in the
nucleus
RNA
Single strand
Sugar is ribose
Has Uracil
Short molecule
Not self replicating
Found in nucleus and
cytoplasm
Similarities between DNA and RNA
Both are nucleic acids
Both contain adenine, guanine and cytosine
nucleotides
Operate together to produce specific proteins
Learning Check
1. What does RNA stand for?
2. What three bases do DNA and RNA have in
common?
3. What base does RNA have instead of
Thymine?
4. Where do you find both DNA and RNA?
5. Where else will you find RNA?
H.L Objectives
AT THE END OF THIS SECTION YOU SHOULD KNOW …. .
DNA STRUCTURE – DEOXYRIBOSE SUGAR, SUGAR, PHOSPHATE AND 4 NAMED
NITROGENOUS BASESNUCLEOTIDE STRUCTURE
SPECIFIC PURINE AND PYRAMIDINE COUPLES – COMPLEMENTARYBASE PAIRS
HYDROGEN BONDINGDOUBLE HELIX
NUCLEIC ACID STRUCTURE
Higher Level
Nucleotides
Nucleotides are carbon ring structures containing
nitrogen linked to a 5-carbon sugar (a ribose)
5-carbon sugar is either a ribose or a deoxyribose
In eukaryotic cells nucleic acids are either:
Deoxyribose nucleic acids (DNA)
Ribose nucleic acids (RNA)
OH
OCH2
Sugar
H
HH
A Nucleotide
OH
NH2
N
N N
N
BaseP
O
OH
HO O
Phosphate
2’3’
4’
5’
1’
H+
-
Coding and Non Coding Parts
Non coding StructuresSugar – Phosphate
Coding StructuresBase Sequences
Purine Bases
Adenine and Guanine
Double ringed molecular structures
Known as Purine Bases
Pyrimidine Bases
Thymine and Cytosine
single ringed structures
Known as Pyrimidine bases
Pyrimidines
NH2
O
N
N NH
N
Guanine
N
N
Adenine
N
N
NH2
N O
NH2
N O
NH2
NCytosine
Purines
Uracil(RNA)CH3
N ON
O
NH
N ON
O
NH
Thymine(DNA)
Base Numbers
Number of Purine Bases =
Number of Pyrimidine Bases
This led to the discovery of Base Pairing
NO
H
NO
N
NH C
ytosin
e
H
O
NN
N
N
N
H
H
Guanine -+
+
+
-
-
Base PairingGuanine And Cytosine
Three Hydrogen Bonds
CH 3N
O
N
ON
H+
- ThymineN
NN
N
HN H
-
+Adenine
Base PairingAdenine And Thymine
Two Hydrogen Bonds
Base PairingGuanine And Thymine
CH 3
NO
N
O
NH+
- Thymine
H
O
NN
N
N
N
H
H
Guanine
+
+
-
The Watson - Crick Model Of DNA
3.4 nm1 nm
0.34 nm
Majorgroove
Minorgroove
A T
T AG C
C G
C GG C
T A
A T
G CT A
A TC G
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What have you learned
Can you ……………… 1. Outline the simple structure of DNA2.Name the four bases and the base pairs in
DNA3.Distinguish between coding and non coding
structures4.Define triplet base code5.Outline the structure of RNA6.Name the bases in RNA and know the
function of mRNA7.Discuss the replication of DNA
End