Explain the function of mitosis
WHAT is the function of mitosis?
The functions (the jobs mitosis does for an organism) are:
- Growth — increasing the number of cells so the organism gets bigger.
- Repair — replacing cells damaged or worn out (e.g. healing a cut).
- Replacement / maintenance — constantly renewing short-lived cells (skin, gut lining, blood).
- Asexual reproduction — in some organisms (e.g. Hydra budding, plant runners), making whole new individuals.
WHY must the copies be identical?
So the deep reason: a multicellular body only works if all cells share the same genome. Mitosis is the mechanism that guarantees this fidelity.
HOW does mitosis achieve identical daughters? (Derivation from first principles)
We don't need to memorise — we can reason out what mitosis MUST do.
Step 1 — State the goal. Start: 1 cell with a chromosome number we call (diploid). Required end: 2 cells, each also , each identical.
Why this step? Defining the start and required end tells us exactly what problem the cell must solve.
Step 2 — Conservation requirement. For each daughter to have a full copy, the DNA must first be duplicated.
If a cell has molecules of DNA and just split, each daughter would get → half the instructions. Unacceptable. Therefore:
Why this step? This is simple conservation of material. To give two cells a full set, you must build a double set first. This duplication happens in the S phase (DNA synthesis) of interphase, before mitosis.
Step 3 — Each duplicated chromosome = two identical sister chromatids. After replication, each chromosome is two sister chromatids joined at a centromere.
Why this step? The "identical" requirement is satisfied here — the copy is made by template base-pairing, so the chromatids are exact duplicates.
Step 4 — Equal segregation. The sister chromatids are pulled apart so that one chromatid from every chromosome goes to each pole.
Why this step? Splitting sisters (not pairs of different chromosomes) is the key trick — it guarantees each side gets one copy of every gene, hence identical.
Conclusion (the formula of mitosis):
Worked Examples
Active Recall
Recall Q: What are the 4 functions of mitosis? (cover the answer!)
Growth, repair, replacement/maintenance, and asexual reproduction.
Recall Q: Why must daughter cells be genetically identical?
So every body cell carries the same DNA instructions and functions correctly; loss of this fidelity → disease/cancer.
Recall Q: What happens
before mitosis to make identity possible? DNA replication in S phase, creating identical sister chromatids.
Recall
Feynman: explain to a 12-year-old Your body is like a city made of tiny bricks called cells. When you grow taller or heal a scraped knee, you need more bricks. Mitosis is the machine that copies a brick perfectly: first it photocopies the brick's instruction sheet, then it splits the brick into two — each one getting a complete instruction sheet. So both new bricks are exact twins of the old one and know exactly what to do. That's how you grow and heal without messing things up!
Flashcards
What is the function of mitosis?
Are mitosis daughter cells identical or varied?
Does mitosis change the chromosome number?
What process makes gametes instead of mitosis?
What must happen before mitosis for identical copies?
How many cells result after k rounds of mitosis from one cell?
A human body cell (46 chromosomes) divides by mitosis — how many in each daughter?
Name two organisms that use mitosis for asexual reproduction.
What links uncontrolled mitosis to disease?
What is split during anaphase of mitosis?
Connections
- Cell Division
- Stages of Mitosis (PMAT)
- Interphase and the Cell Cycle
- Meiosis vs Mitosis
- DNA Replication
- Chromosomes and Chromatids
- Cancer and Uncontrolled Cell Division
- Asexual Reproduction
Concept Map
Hinglish (regional understanding)
Intuition Hinglish mein samjho
Dekho, mitosis ka simple matlab hai: ek cell se do bilkul identical cells banana. Yeh body ke liye photocopy machine ki tarah hai. Jab tum bade hote ho (growth), ya jab cut lag jaaye aur wo heal hota hai (repair), ya purani skin/blood cells replace hoti hain — yeh sab mitosis se hota hai. Kuch jeev jaise Hydra ya plants asexual reproduction ke liye bhi mitosis use karte hain. Isko yaad rakhne ka mnemonic: GRRR — Growth, Repair, Replacement, Reproduction.
Ab sabse important baat: daughter cells genetically identical hone chahiye, kyunki body ki har cell mein same DNA instruction book honi chahiye. Agar copy galat ho jaaye to cell apna kaam bhool jaata hai — yahi cancer ka basic idea hai. Isiliye mitosis mein chromosome number change nahi hota: 2n se 2n. Yeh meiosis se alag hai — meiosis gametes (sperm, egg) banata hai aur number aadha kar deta hai, variation laata hai. Confuse mat hona!
Logic se samjho: do full copies dene ke liye, pehle cell apna DNA double karta hai (S phase) — har chromosome ke do identical sister chromatids ban jaate hain. Phir mitosis in sisters ko alag karke dono sides bhejta hai, taaki har daughter ko poora set mile. Bas, conservation of material ka simple funda hai: pehle double karo, phir baant do. Aur agar ek cell baar-baar divide kare to cells ho jaate hain (k = rounds).