HS-LS1-4: Mitosis and Cell Differentiation
Also called NGSS HS-LS1-4 · Topic: Inheritance and Variation of Traits · Life Science
The Official Wording
Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.
Assessment boundary: Assessment does not include specific gene control mechanisms or rote memorization of the steps of mitosis.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What HS-LS1-4 Means in Plain English
Students use a model, such as a diagram, animation or microscope slide, to show how one fertilized egg becomes a body of trillions of cells. Mitosis makes more cells with identical DNA, and differentiation turns those copies into specialized cells like muscle, nerve and skin.
Students are not expected to recite the phases of mitosis or explain the gene switches that control differentiation. The idea builds on MS-LS1-1 and MS-LS1-3, where cells and body systems appear, and supports HS-LS1-1 on how DNA codes for proteins.
HS-LS1-4 I Can Statements
- I can explain how mitosis makes new cells with identical DNA.
- I can describe how differentiation produces specialized cells.
- I can use a model to show how an organism grows.
HS-LS1-4 Worked Example
A microscope investigation that compares the tip of an onion root with the region just behind it.
Where in a growing onion root are cells dividing, and what happens to cells farther from the tip?
Set It Up: Prepared onion root tip slides, compound microscopes at 400x and a tally sheet.
- Find the zone just behind the root cap and count 100 cells, tallying any with visible, condensed chromosomes.Tip zone: 18 of 100 dividing
- Move about 2 mm farther up the root and count 100 cells again.Upper zone: 1 of 100 dividing
- Compare the cell shapes in the two zones.Tip: small, boxy cells. Upper: long, stretched cells
- Pool tallies from all lab groups to check the pattern.Every group finds most dividing cells near the tip
Cell division was concentrated near the root tip, while cells farther back had stopped dividing and grown longer.
Why it works: Mitosis near the tip supplies new cells, and as the root grows past them those cells lengthen and differentiate into specialized root tissues that carry the same DNA.
Common Mistakes with HS-LS1-4
Thinking different cells have different DNA
“Muscle cells have muscle DNA”
Try this: Almost every body cell carries the same DNA. Differentiated cells differ because they switch different genes on and off.
Growth means cells get bigger
“Kids grow because their cells grow”
Try this: Growth mostly comes from making more cells through mitosis. Each cell roughly doubles and then splits in two, so cell size stays about the same.
Memorizing phases instead of purpose
Reciting phase names but unable to say why mitosis matters
Try this: Explain what mitosis achieves: two cells with identical DNA, used for growth, repair and replacing worn-out cells like skin.
Where HS-LS1-4 Fits
Practice HS-LS1-4
Quick Check
- Your skin cells and nerve cells look very different. Do they have different DNA?
- Where would you look for dividing cells in a plant root?
- How does mitosis help heal a cut?