1. Coding for Life Introduction
Nucleic acids are very special chemicals in cells which have the information ...
to control cellular activities, and
concerned with the transmission of
inherited characteristics.
All nucleic acids are made of simple repeating units (monomers), called nucleotides. They are linked together to form lengthy strands, nucleic acids (polymers).

2. Coding for Life Nucleic acids There are two types of nucleic acids ...
Deoxyribonucleic acid (DNA).
This nucleic acid is a major component of chromosomes. Found primarily in the nucleus, a small amount is found in mitochondria and chloroplast. There are two types of DNA the coding DNA which forms the genes and the non-coding DNA.
Ribonucleic acid (RNA).
Is involved in the ‘reading’ of the DNA information. Found in the nucleus and cytoplasm of cells.

3. General structure of nucleotides
Nucleotides are the building blocks (monomers) of the two different nucleic acids (RNA and DNA). The best way to understand the structure of DNA and RNA is to study the nucleotides. Each nucleotide consists of three parts:
a sugar molecule,
a phosphate group,
a nitrogenous base.

4. Detail of the 3 parts of nucleotides
1. Phosphate group
DNA and RNA have the same phosphate group, which links adjacent sugars together into a strand of great length.
2. Sugars
Deoxyribose sugar is found only in DNA. Ribose sugar is found only in RNA.
DNA has Deoxyribose sugar
RNA has Ribose sugar
   

5. Purine bases consist of a two-ringed structure (the longer bases).
3. Nitrogenous bases
One example of a nitrogenous base occurs in each nucleotide. These bases comprise the coded genetic message. Two types of bases, namely,
3.1 Purines:
Purine bases consist of a two-ringed structure (the longer bases).
Two examples Adenine and Guanine.
    G

6. Two examples for DNA only Cytosine and Thymine.
3.2 Pyrimidines
Pyrimidine bases consist of a single-ringed structure (the shorter bases).
Two examples for DNA only Cytosine and Thymine.
Two examples for RNA only Cytosine and Uracil.
    C C

7. Nitrogenous bases for In RNA Thymine is replaced by Uracil DNA RNA
   
DNA
RNA
Adenine
Thymine
Uracil
Cytosine
Guanine
In RNA Thymine is replaced by Uracil

8. Coding for Life – DNA structure
Phosphate group links two sugars together
Deoxyribose sugar
Two weak hydrogen bonds
Three weak hydrogen bonds
Complementary
nitrogenous bases
A simplified representation of a portion of a DNA molecule

9. Linking the nucleotides in a DNA molecule
Step one: To form a single strand
The deoxyribose sugar of one nucleotide joins with the phosphate group of another nucleotide. These nucleotides are joined by a strong sugar-phosphate bond.
Step 2: Formation of a double strand
A single strand is joined to another strand with complementary nitrogenous bases. These complementary bases are linked by weak hydrogen bonds.
Phosphate group links two sugars together
The phosphate group and the sugar form the frame (legs) and the base pairs form the steps of the ladder.
The two strands together form a ladder-like structure.

10. Pairing of nitrogenous bases for DNA (complementary base pairs)
   
A purine (long) and a pyrimidine
(short) base pair with each other. Why?
(Ensuring that the space/width between the two legs of the ladder stays the same)
Thymine (short) always pairs with Adenine (long).
Cytosine (short) always pairs with Guanine (long).

11. Pairing of nitrogenous bases
Cytosine is pairing with Guanine
Thymine is pairing with Adenine
The total length of DNA in mammal cells is ± 2 meters – in your body ±10 billion km.

12. Number of nitrogenous bases in a DNA molecule
Because the nitrogenous bases are paired in a specific way the following deductions are important:
The number of cytosine bases present in a specific DNA molecule is?
Equal to the number of guanine bases.
The number of Adenine in a specific DNA molecule = ?
is equal to the number of thymine.
In the cell the DNA ladder is not a flat structure. It is twisted and forms a double helix. See the two presentations below.

13. Characteristics of a DNA molecule
Is a very long molecule
Has a double helix structure
Sequence in which bases pairs can occur is
unlimited.
There are equal cytosine bases than guanine
bases and equal adenine bases than thymine
bases in a specific DNA molecule.

14. Role of DNA that codes for proteins
DNA carriers the coding for all inheritance characteristics on the chromosomes and are called genes.
DNA controls the structure and functioning of a cell by means of proteins which are produced according to the sequence of the bases in the DNA molecule.
DNA is able to make mRNA (coding RNA).

15. Role of non-coding DNA Non-coding DNA molecules are components of
an organism's DNA that do code for proteins.
However, it has been known for decades that
many non-coding sequences are functional.
Some non-coding DNA is transcribed into
functional non-coding RNA molecules for
example transfer RNA, ribosomal RNA and
regulatory RNAs), while others has unknown
functions.