G1 Phase (Gap 1): Cell Growth Without DNA Replication
Biology · Cell Cycle and Cell Division · NEET
G1 (Gap 1) is the first part of interphase. It is the time gap between the end of mitosis and the start of DNA replication (S phase). In G1 the cell is metabolically active and grows in size, but it does NOT replicate its DNA. Memory hook: "G1 = Grow, not copy" — the cell gets bigger, the DNA stays the same (2C).
G1 is the first gap of interphase: the cell grows and stays at 2C DNA (no replication). DNA is copied only in S phase. At the end of G1 a cell may instead exit into the G0 quiescent stage and stop dividing.
Your doubts, answered
Does DNA replication happen in G1 phase?
No. This is the most common mistake. DNA replication happens ONLY in the S (Synthesis) phase, not in G1. In G1 the cell grows and makes proteins and organelles, but the amount of DNA stays at 2C. NEET loves to test this: 'DNA synthesis takes place in G1' is always WRONG.
Is the cell active or resting during G1?
The cell is fully active. G1 is part of interphase, which was once wrongly called the 'resting phase'. In G1 the cell is metabolically active and continuously grows. Nothing is resting — the cell is busy preparing for DNA replication.
What phase comes before G1?
M phase (mitosis) comes before G1. NCERT defines G1 as 'the interval between mitosis and the initiation of DNA replication'. So the order for one cycle part is: M (division) then G1 (growth) then S (DNA copy). G1 is the fresh start of a new cell's life before it decides to divide again.
What is the difference between G1 and G0?
G1 is an active gap where the cell is preparing to move into S phase and divide. G0 (quiescent stage) is when a cell EXITS G1 and stops dividing altogether — like heart or nerve cells. A G0 cell is still metabolically active but no longer proliferates unless called upon. So the exit door to G0 is located at the end of G1.
Does the DNA content or chromosome number change in G1?
No change happens in G1. At G1 the DNA content is 2C and the chromosome number is 2n (diploid). Both stay exactly the same throughout G1. Only in S phase does DNA double from 2C to 4C — but even then the chromosome number stays 2n.
⚠️ The NEET trap ✗ During cell growth, DNA synthesis takes place in G1 phase. ✓ DNA synthesis (replication) takes place ONLY in the S phase. In G1 the cell grows and is metabolically active but does NOT replicate its DNA. 🧠 G1 = Grow, not copy. If a question links DNA synthesis or doubling of DNA to G1, it is a trap — copying is always the S phase.
Real NEET questions
NEET 2020
Identify the correct statement with regard to G1 phase (Gap 1) of interphase.
A · Cell is metabolically active, grows but does not replicate its DNA ✓
B · Nuclear division takes place
C · DNA synthesis or replication takes place
D · Reorganization of all cell components takes place
Solution: During G1 the cell is metabolically active and continuously grows but does NOT replicate its DNA. DNA replication is the S phase, nuclear division is M phase, and reorganization of cell components is M phase — so only option A describes G1.
NEET 2016 Phase 2
During cell growth, DNA synthesis takes place in
A · S phase ✓
B · G1 phase
C · G2 phase
D · M phase
Solution: DNA synthesis (replication) occurs only in the S (synthesis) phase, when DNA doubles from 2C to 4C without any change in chromosome number. G1 is the gap before replication where the cell grows but does not copy DNA, so G1 is wrong.
NEET 2021
Match List-I with List-II: (a) S phase (b) G2 phase (c) Quiescent stage (d) G1 phase | (i) Proteins are synthesized (ii) Inactive phase (iii) Interval between mitosis and initiation of DNA replication (iv) DNA replication
A · (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii) ✓
B · (a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
C · (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
D · (a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
Solution: G1 = interval between mitosis and initiation of DNA replication (iii). S = DNA replication (iv), G2 = proteins synthesized (i), Quiescent G0 = inactive phase (ii). This gives (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii).
Solved Cell Cycle and Cell Division NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The cell grows bigger, makes proteins and organelles, and gets ready to copy its DNA. It stays metabolically active but does NOT copy its DNA in G1.
Why is G1 called Gap 1?
It is the first gap (time interval) inside interphase, sitting between the M phase and the S phase. 'Gap' just means the period before DNA replication starts.
Is G1 phase part of interphase?
Yes. Interphase has three parts in order: G1, S, and G2. G1 is the first one. Interphase makes up more than 95% of the total cell cycle.
What is the DNA content and chromosome number at G1?
DNA content is 2C and chromosome number is 2n (diploid). Both stay unchanged all through G1.
What decision is made at the end of G1?
The cell decides either to continue into S phase and divide, or to exit into the G0 (quiescent) stage and stop dividing. So the G1/S checkpoint is a key control point.
