Meiosis — the reduction division
Meiosis (all of 17.3 is Extended — there are no Core statements) is a reduction division: a diploid parent cell (two sets of chromosomes) gives haploid cells (one set) that are genetically different from one another and from the parent. Both halves of that outcome carry marks. The syllabus requires the outcome only — the named stages are not examinable. Contrast with mitosis (17.2), which maintains the number and gives identical cells.
Gametes — why they must be haploid
Gametes — egg and sperm cells in humans, egg cells and pollen in flowering plants — are what meiosis is involved in producing, and each carries a haploid chromosome number. At fertilisation two haploid gametes fuse and the diploid number is restored in the zygote: in humans 23 + 23 = 46, one set from each parent. If gametes were diploid instead, the chromosome number would double every generation — so the halving must happen before fertilisation.
Genetic variation — no two gametes alike
Genetic variation begins at meiosis: each gamete carries a different combination of alleles, so no two gametes from the same parent are identical. That is why siblings from the same two parents differ — each grew from a different sperm and egg cell. The mechanisms (crossing over, independent assortment) are not required by 0610; only the outcome — genetically different cells — is examinable. These haploid gametes are what fuse in the 17.4 inheritance diagrams.
Drawn from real examiner reports.
Human gametes have 23, not 46
A human body cell is diploid with 46 chromosomes (23 pairs); a human egg or sperm cell is haploid with 23. Candidates who give the gamete 46 then make the zygote 92, or halve at the wrong step and report a zygote of 23. Halve once, at meiosis, then add the two haploid sets at fertilisation: 23 + 23 = 46 in the zygote.
Meiosis ≠ mitosis outcome
Meiosis halves the chromosome number and gives genetically different cells. Mitosis (17.2) maintains the number and gives identical cells. Writing "meiosis produces cells identical to the parent", or that it keeps the number the same, describes mitosis and scores zero. Quick check: gametes, halving or variation → meiosis; growth, repair or replacement → mitosis.
Flagged w22 P12 Q35 — the same swap, reported in reverse (mitosis credited with variation)
Right features, wrong name
Examiners report candidates who know both sets of features but attach them to the wrong process — describing halving and variation, then labelling it "mitosis". Revise each name welded to its function: meiosis means gametes, halved, different; mitosis means growth, maintained, identical. Before moving on, check that the label you wrote matches the description underneath it.
Flagged w22 P31 Q2c — features known, names swapped
Phonetic spellings lose the mark
"Meosis" and "meitosis" are reported as too ambiguous to credit — the examiner cannot tell which process is meant, so no mark is given. Spell each in full: m-e-i-o-s-i-s and m-i-t-o-s-i-s. In a comparison question the two words sit next to each other, so one hybrid spelling can sink both halves of the answer at once.
Flagged s22 P41 Q6a — "meitosis" for mitosis, "meosis" for meiosis
Meiosis is not ovulation
Meiosis is the cell division that produces an egg cell with a haploid chromosome number. Ovulation is the release of an already-formed egg cell from the ovary into the oviduct — a later event in the menstrual cycle, not a division at all. "Meiosis happens when the egg is released" fuses two separate events and earns no credit — division first, release later.
Flagged s22 P31 Q4a ii — ovulation confused with meiosis
"Cell division" is too vague
Calling meiosis "a type of cell division" describes mitosis equally well, so it cannot score. The definition needs three elements: a reduction division, the chromosome number halved from diploid to haploid, and the resulting cells genetically different. Drop any one of the three and the mark scheme has nothing left to reward.
Answer in a fixed order
For any describe/explain meiosis question, run REDUCTION → HALVED → DIFFERENT → GAMETES: it is a reduction division; the chromosome number is halved, diploid to haploid; the cells produced are genetically different; meiosis produces gametes. Four points, four marks.
Name both processes in a comparison
If the question compares meiosis with mitosis, state the mitosis side too — chromosome number maintained, daughter cells genetically identical. "The other type of division" does not secure the comparison mark; the examiner needs both names attached to both outcomes.
Never write the stages
Prophase I, metaphase I, crossing over and independent assortment sit outside 0610 — the syllabus states that details of the stages of meiosis are not required. Writing them costs time and cannot earn a mark however accurate they are. Give the outcome instead.
Quote the numbers you are given
In a chromosome-number scenario, justify with the actual figures — "14 down to 7, so the number is halved: meiosis". Naming the process without using the data printed in the question leaves the justification mark unclaimed.
(This whole topic is Extended/Supplement content - the Cambridge 0610 syllabus gives no Core statements for 17.3 Meiosis.)
(Extended) Meiosis: a reduction division in which the chromosome number is halved from diploid to haploid, resulting in genetically different cells. (Details of the stages of meiosis are not required by the 0610 syllabus.)
(Extended) Meiosis and gametes: meiosis is involved in the production of gametes (egg cells and sperm cells in humans; egg cells and pollen in flowering plants). Each gamete produced carries a haploid chromosome number.
Diploid vs haploid (recap from 17.1): a diploid nucleus contains two sets of chromosomes (in a human diploid cell, 23 pairs = 46 chromosomes); a haploid nucleus contains one set of chromosomes (23 in a human gamete). Meiosis converts a diploid parent cell into haploid gametes.
Why gametes must be haploid: at fertilisation, a haploid sperm cell fuses with a haploid egg cell to restore the diploid chromosome number in the zygote - one full set of chromosomes from each parent. If gametes were diploid, the chromosome number would double every generation.
(Extended) What is meiosis involved in producing?
(Extended) (a) Define meiosis.
(b) State what meiosis is involved in producing.
