6. MOLECULAR BASIS OF INHERITANCE
PROPERTIES OF GENETIC MATERIAL
(DNA v/s RNA)
A genetic material must have the following properties:
- Ability to generate its replica (Replication).
- Chemical and structural stability.
- Provide the mutations that are required for evolution.
- Ability to express as Mendelian Characters.
Reasons for stability (less reactivity) of DNA
Reasons for mutability (high reactivity) of RNA
Double stranded
Single stranded
Presence of thymine
Presence of Uracil
Absence of 2’-OH in sugar
Presence of 2’-OH in sugar
- RNA is unstable. So, RNA viruses (E.g. Q.B bacteriophage, Tobacco Mosaic Virus etc.) mutate and evolve faster.
- DNA strands are complementary. On heating, they
separate. In appropriate
conditions, they come together. In Griffith’s experiment, some properties of DNA of the heat killed
bacteria did not destroy. It indicates the stability of DNA.
- For
the storage of genetic information, DNA is better due to its stability. But for
the transmission of genetic information, RNA is better.
- RNA
can directly code for the protein synthesis, hence can easily express the
characters. DNA is dependent on RNA for protein synthesis.
RNA WORLD
- RNA was the first genetic material.
- It acts as genetic material and catalyst.
- Essential life processes (metabolism, translation, splicing etc.) evolved around RNA.
- DNA evolved from RNA for stability.
- Topic 1: The DNA
- Topic 2: The Search for Genetic Material
- Topic 3: Properties of Genetic Material, RNA World
- Topic 4: DNA Replication
- Topic 5: Transcription
- Topic 6: Genetic Code, Types of RNA
- Topic 7: Translation (Protein Synthesis)
- Topic 8: Regulation of Gene Expression, Operon Concept
- Topic 9: Human Genome Project (HGP)
- Topic 10: DNA Fingerprinting