Ch 6. Molecular Basis of Inheritance (stack 2) Flashcards
Mention any two criteria that a molecule must full fill to act as genetic material.
- It should be able to generate its replica (Replication).
- It should chemically and structurally be stable.
DNA is a better genetic material than RNA. Justify with two reasons
- DNA chemically is less reactive and structurally more stable when compared to RNA.
- The presence of thymine at the place of uracil also confers additional stability to DNA.
List any three criteria that a molecule has to fulfil to act as a genetic material
- It should be able to generate its replica (Replication).
- It should chemically and structurally be stable.
- It should provide the scope for slow changes (mutation) that are required for evolution.
Why is DNA molecule a more stable genetic material than RNA? Explain
- DNA is structurally more stable because of its double-stranded nature.
- 2’-0 H group present at every nucleotide in RNA is a reactive group and makes RNA labile and easily degradable. RNA is also now known to be catalytic, hence reactive. Therefore, DNA chemically is less reactive and structurally more stable when compared to RNA.
- The presence of thymine at the place of uracil also confers additional stability to DNA
- Define replication.
The process of synthesis of two new DNA from a parental DNA is called replication.
Why replication in DNA is referred to as semi-conservative replication?
It is because , in the resulting daughter DNA only one strand is newly synthesised and the other strand is from the parental DNA conserved as it is.
Name the enzyme involved in the polymerization of nucleotides during DNA replication.
DNA polymerase
Mention the template polarity on which replication occurs continuously
3’ → 5
Mention the template polarity on which replication occurs discontinuously.
5’ → 3’
Name the enzyme which joins discontinuously synthesized fragments of DNA during DNA replication
DNA ligase
What is origin of replication?
A definite region in DNA, where replication begins
In which phase of the cell cycle DNA replication occurs?
S-Phase
Mention the functions of DNA polymerase and DNA ligase during replication
DNA polymerase - Catalyse polymerisation of a large number of nucleotides in a very short time.
DNA ligase - The discontinuously synthesised fragments lagging strand are later joined.
Draw a labelled diagram of replication fork
Explain the role of enzymes involved in DNA replication.
Unwindase/ Helicase - Unwinding of DNA double helix
Topoisomerase/gyrase-Reduces the strain between two strands of DNA
DNA polymerase - Synthesis of new strand by linking nucleotides
DNA ligase - joining of fragments in the lagging strand
Define transcription
” Both the strands of DNA do not act as templates during transcription”. Justify with a reason
Both the strands of DNA do not act as templates during transcription because:
- If both strands act as a template, they would code for two different proteins, and this would complicate the genetic information transfer machinery.
- The two RNA molecules if produced simultaneously would be complementary to each other, hence would form a double stranded RNA. This would prevent RNA from being translated into protein .
