Block 4 · Heredity · MCAS Reporting Category 2
Mitosis vs meiosis
Your body divides cells for two reasons: growth and repair (mitosis) and making sex cells (meiosis). This block reviews both, the diploid/haploid math, and how crossing over creates genetic variation. MCAS tests this in both the Heredity and Molecules to Organisms categories.
What you need to know cold
- mitosisCell division — one cell becomes two identical cells. = 2 identical body cells. For growth and repair.
- meiosisCell division that makes 4 sex cells (eggs or sperm) with half the DNA. = 4 unique sex cells (gameteA sex cell — an egg or a sperm. Has half the normal chromosomes.s). For reproduction.
- Body cells are diploidA cell with the full set of chromosomes (2n). Body cells are diploid. (2n). Gametes are haploidA cell with half the chromosomes (n). Eggs and sperm are haploid. (n = half).
- The four stages of mitosis in order: prophaseFirst stage of mitosis. Chromosomes condense and become visible., metaphaseSecond stage of mitosis. Chromosomes line up in the middle., anaphaseThird stage of mitosis. Chromosomes pull apart toward opposite ends., telophaseFourth stage of mitosis. Two new nuclei form and the cell divides. (P-M-A-T).
- Metaphase = Middle. Anaphase = Apart.
- crossing-overWhen paired chromosomes swap pieces during meiosis, increasing variation. during meiosis = homologous chromosomes swap pieces = increases genetic variation.
- Father → daughter = X. Father → son = Y.
- Diploid/haploid math: body cell has 28 chromosomes → gamete has 14.
mitosis
meiosis
gamete
diploid
haploid
prophase
metaphase
anaphase
telophase
crossing-overThe Big Rule for this block
Mitosis copies. Meiosis halves.
If the question is about growth, repair, or identical cells → mitosis. If the question is about gametes, half the chromosomes, or genetic variation → meiosis.
Key vocabulary in 8 languages
Words from this block. Use the row in your home language to help your memory. Many of these words are similar across languages because they come from Greek and Latin roots.
| English | Español | Português | Français | Italiano | Kreyòl | Tiếng Việt | العربية |
|---|---|---|---|---|---|---|---|
| mitosis | mitosis | mitose | mitose | mitosi | mitoz | nguyên phân | انقسام متساوٍ(inqisām mutasāwin) |
| meiosis | meiosis | meiose | méiose | meiosi | meyoz | giảm phân | انقسام منصف(inqisām munaṣṣaf) |
| gamete | gameto | gameta | gamète | gamete | gamèt | giao tử | خلية جنسية(khaliyya jinsiyya) |
| diploid | diploide | diploide | diploïde | diploide | diplowid | lưỡng bội | ثنائي الصيغة الصبغية(thunāʾī aṣ-ṣīgha aṣ-ṣibghiyya) |
| haploid | haploide | haploide | haploïde | aploide | aplowid | đơn bội | أحادي الصيغة الصبغية(uḥādī aṣ-ṣīgha aṣ-ṣibghiyya) |
| chromosome | cromosoma | cromossomo | chromosome | cromosoma | kwomozòm | nhiễm sắc thể | كروموسوم(krūmūsūm) |
| crossing over | entrecruzamiento | crossing over / permutação | enjambement / crossing-over | crossing over | kwazman | trao đổi chéo | عبور كروموسومي(ʿubūr krūmūsūmī) |
The mitosis, meiosis, gamete, diploid, haploid, and chromosome rows use verified translations from the Quick Reference vocabulary table. The crossing over row is new for Block 4 and has NOT yet been independently verified by GPT-5 / Gemini per Ms Brandolini's verification cycle — it relies on cognate consistency (Romance languages) and standard scientific-vocabulary equivalents (Vietnamese, Arabic, Haitian Kreyòl). If a term feels unfamiliar to a native speaker, please tell Ms Brandolini.
The full picture
Mitosis vs meiosis — the two kinds of cell division
What this reading is about
Your body has two reasons to divide cells: growth and repair (making more body cells) and making sex cells (eggs and sperm for reproduction). These two jobs use two different processes:
- mitosisCell division — one cell becomes two identical cells. — makes 2 identical body cells
- meiosisCell division that makes 4 sex cells (eggs or sperm) with half the DNA. — makes 4 unique sex cells (gameteA sex cell — an egg or a sperm. Has half the normal chromosomes.s)
This reading walks through both, the math that goes with them, and the reason meiosis creates genetic variation.
Mitosis: growth and repair
mitosisCell division — one cell becomes two identical cells. is how your body grows and fixes itself. When you need new skin cells, new root cells in a plant, or new blood cells, mitosis is the process.
The key fact: mitosis makes two cells that are identical to the parent cell. Both new cells have the same number of chromosomeDNA wound up tightly into a compact X or rod shape. You see chromosomes when a cell is about to divide.s as the original. If the parent cell was diploidA cell with the full set of chromosomes (2n). Body cells are diploid. (2n = 46 in humans), both daughter cells are also diploid (2n = 46).
chromosomeThe four stages of mitosis: P-M-A-T
Mitosis has four stages that always happen in the same order. MCAS may show you pictures and ask you to identify or order them.
- prophaseFirst stage of mitosis. Chromosomes condense and become visible. — Chromosomes condense and become visible as X-shaped structures. The nuclear membrane starts to break down.
- metaphaseSecond stage of mitosis. Chromosomes line up in the middle. — Chromosomes line up along the middle of the cell. Think: Metaphase = Middle.
- anaphaseThird stage of mitosis. Chromosomes pull apart toward opposite ends. — Chromosomes pull apart toward opposite ends. Think: Anaphase = Apart.
- telophaseFourth stage of mitosis. Two new nuclei form and the cell divides. — Two new nuclei form. The cell splits in two (cytokinesis).
Meiosis: making gametes
meiosisCell division that makes 4 sex cells (eggs or sperm) with half the DNA. is different from mitosis in three important ways:
| Mitosis | Meiosis | |
|---|---|---|
| How many cells? | 2 | 4 |
| Identical or different? | Identical to parent | Different from parent and from each other |
| Chromosome number? | diploidA cell with the full set of chromosomes (2n). Body cells are diploid. (2n) — full set | haploidA cell with half the chromosomes (n). Eggs and sperm are haploid. (n) — half set |
| Purpose? | Growth and repair | Make gameteA sex cell — an egg or a sperm. Has half the normal chromosomes.s (eggs and sperm) |
The diploid/haploid math
Body cells are diploidA cell with the full set of chromosomes (2n). Body cells are diploid. — they have the full set of chromosomes, written as 2n. In humans, 2n = 46.
Gametes (eggs and sperm) are haploidA cell with half the chromosomes (n). Eggs and sperm are haploid. — they have half, written as n. In humans, n = 23.
When egg and sperm combine at fertilization: n + n = 2n. That's 23 + 23 = 46. The new organism has the full set again.
What does a father pass to his children?
A father has 22 pairs of autosomes plus one pair of sex chromosomes (XY). He makes sperm through meiosis. Each sperm gets:
- 22 autosomes (one from each pair) plus either an X or a Y.
So:
- Father → daughter: 22 autosomes + the X chromosome.
- Father → son: 22 autosomes + the Y chromosome.
The father's sperm determines the sex of the child. If the sperm carries X, the child is female (XX). If the sperm carries Y, the child is male (XY).
Crossing over: why siblings are different
crossing-overWhen paired chromosomes swap pieces during meiosis, increasing variation. happens during meiosis. When homologous chromosomes (matching pairs — one from mom, one from dad) line up, they swap small sections of DNA. After the swap, each chromosome has a new combination of alleles.
This is a major source of genetic variation. Even though two siblings have the same parents, each egg and each sperm carries a different mix of genetic material because of crossing over.
Quick check: mitosis or meiosis?
- "Makes new root cells" → mitosis
- "Makes new skin cells" → mitosis
- "Makes eggs or sperm" → meiosis
- "Daughter cells are identical" → mitosis
- "Daughter cells are haploid" → meiosis
- "Increases genetic variation" → meiosis (crossing over)
Why this matters for MCAS
Cell division questions appear in both the Heredity and Molecules to Organisms reporting categories. The most common question types are:
- Order the stages of mitosis from pictures (P-M-A-T).
- "What is the direct product of meiosis?" → gametes, never body cells.
- Diploid/haploid math — body cell has X chromosomes, how many in a gamete?
- "Why does meiosis exist?" → to make haploid gametes with half the chromosomes from each parent.
- "What does crossing over do?" → increases genetic variation.
If you can answer those five, you have the cell-division portion of MCAS covered.
Diagram: what mitosis looks like at the middle
The picture you'll see most on the test: chromosomes lined up in a straight row across the middle of the cell. This is metaphase — M = Middle. If you can recognize this single image, you can usually answer two or three questions about mitosis stages.
Diagram: the whole path of meiosis
One parent cell at the top (diploid, 2n). Two divisions later, four gametes (haploid, n) at the bottom. Notice that meiosis takes two divisions to get there — Meiosis I separates the pairs, Meiosis II separates the sister chromatids. The two chromosome colors show the two pairs you start with.
Diagram: mitosis vs meiosis, side by side
Both columns start with the same cell. Read down each column to see what happens. Mitosis (left): one division, two identical daughter cells. Meiosis (right): two divisions, four different gametes — different because of crossing over (the orange dot) in meiosis I. The Big Rule for this block lives at the bottom of this picture.
Pictures to recognize on the test
| The picture shows… | The answer is… |
|---|---|
| Chromosomes condensed into X shapes, scattered in the cell (not lined up). | Prophase. First stage of mitosis. |
| Chromosomes lined up in a straight row across the middle of the cell. | Metaphase. M = Middle. |
| Chromosomes being pulled apart toward opposite ends of the cell. | Anaphase. A = Apart. |
| Two groups of chromosomes with new nuclei forming; cell pinching in the middle. | Telophase. Two new nuclei, cell about to split. |
| Two chromosomes swapping pieces. | Crossing over (increases genetic variability). |
| Karyotype with 22 pairs + XY. | Male. Father gives X to daughters, Y to sons. |
| Karyotype with 22 pairs + XX. | Female. |
Pattern rules
| If the question says… | Pick… |
|---|---|
| "Order of mitosis stages" (4 pictures). | Find P-M-A-T order: condensing → middle → apart → two nuclei. |
| "Process that makes new root cells / skin cells / growth." | Mitosis. |
| "Mitosis daughter cells are…" | Identical to the parent (same chromosome number). |
| "Direct product of meiosis." | Egg or sperm (NEVER muscle / nerve / skin). |
| "Importance of meiosis." | Makes haploid gametes with half from each parent. |
| "Body cell has 28 chromosomes — egg has?" | Half = 14. |
| "What does a father pass to his daughter?" | 22 autosomes + the X. |
| "Crossing over does what?" | Increases genetic variability. Homologous chromosomes exchange genetic material. |
Where to practice
Practice the Block 4 — Mitosis vs meiosis test on Pear Assessment. You can retake it as many times as you want — the questions and answer choices shuffle each time, so every attempt feels a little different. Try it without looking at this page first. If you get stuck, come back, look up the pattern, then try again.