S Phase
The phase where DNA synthesis or replication takes place, doubling the DNA content.
What is S Phase?
The biological process of producing two identical replicas of DNA from one original DNA molecule.
Key points
- To understand the primary event of DNA replication in the cell cycle.
- To recognize the change in DNA content and chromosome structure during S phase.
- To identify the role of S phase in ensuring genetic continuity.
- To appreciate the regulatory mechanisms involved in DNA synthesis.
Common exam trap
Confusing S phase with G2 phase (which is for preparation for mitosis).
Definitions
- Term
DNA Replication
- Meaning
The biological process of producing two identical replicas of DNA from one original DNA molecule.
- Term
Sister Chromatids
- Meaning
Two identical copies of a single chromosome that are joined to each other by a centromere, formed during DNA replication.
- Term
Semi-conservative Replication
- Meaning
A mode of DNA replication in which each of the two new DNA molecules produced contains one strand from the original DNA molecule and one newly synthesized strand.
Learning objectives
To understand the primary event of DNA replication in the cell cycle.
To recognize the change in DNA content and chromosome structure during S phase.
To identify the role of S phase in ensuring genetic continuity.
To appreciate the regulatory mechanisms involved in DNA synthesis.
Prerequisites
Understanding of DNA structure and function.
Basic knowledge of cell division (mitosis/meiosis).
Familiarity with interphase and its stages (G1, S, G2).
Common mistakes
Confusing S phase with G2 phase (which is for preparation for mitosis).
Assuming DNA content remains the same after S phase.
Forgetting that histone synthesis also occurs.
Keywords
S phase
DNA replication
Interphase
Cell cycle
Sister chromatids
Histones
DNA polymerase
Semi-conservative
Practice preview
If a cell is in the S phase, what can be inferred about its state regarding the cell cycle?…
medium
During which phase of the cell cycle does the amount of DNA in a diploid cell (2n) double?…
easy
If a mutation occurs during DNA replication in the S phase, leading to an altered DNA sequence, what is the most likely consequence for the cell and its daughter cells?…
hard