How cells specialize, and what stem cells are
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
Read this first
Cycle wheel (model, not to scale), clockwise from the top
G1, S, G2, mitosis (M), cytokinesis. A side branch labeled G0 leaves the wheel near the start of G1. Two branches leave the wheel after G1. Branch A ends at a drawn cell A that is striped, with one nucleus in the middle. Branch B ends at a drawn cell B with a round body, branching projections and one long projection. Genes in cells 1 and 2 (model data), 2 rows. Columns: cell, gene for myosin, gene for a nerve-signal protein. cell 1, on, off. cell 2, off, on. Myosin helps muscle cells contract. On means the cell is using the gene; off means the gene is in the DNA but unused.
Esme joins the drawing and the card. Which statement fits both?
- A matches cell 2, since the larger cell is the nerve cell
- A matches cell 1, and A and B carry the same DNA but use different genes
- A matches cell 1, and A and B switch on the same genes at the same time
- A matches cell 1, and B lacks the myosin gene in its DNA
Off means the gene is in the DNA but unused. Jun joins the drawing and the card. Which statement fits both?
- The tip's daughter cells specialize into different tissues by using different genes
- A and B can still divide into any plant tissue, because specialized cells keep that ability
- A and B cannot come from the tip, since plants have no dividing cells
- A and B differ because the tip hands them different DNA
In cells with a nucleus, genes are used (turned into RNA) inside the nucleus. Pia wants drawn cell A to switch on a new gene. Why can it not do this?
- Genes are used in the nucleus, and A has no nucleus, so it has no gene to switch on
- A has switched off its genes for good
- A is specialized, so it divides into a cell that has a nucleus
- A has different DNA from the cells it came from
Stem cell rounds with growth (model data)
round stem cells specialized cells 0 1 0 1 2 0 2 2 2 In the first round, the stem cell divides into two stem cells. In later rounds, each stem cell makes one stem cell and one specialized cell. Specialized cells do not divide again. Every cell keeps its nucleus and gets a copy of its parent's DNA.
Kira continues the table to the third round. How many cells then carry a copy of the first stem cell's DNA?
- 6 cells, since every daughter gets a copy of the DNA
- 2 cells, since specialized cells get different DNA
- 4 cells, the number of specialized cells made
- 8 cells, since each of the 4 cells divides again
Each round, every stem cell makes one stem cell and one specialized cell. Specialized cells do not divide again. Luz works backward from the sample. How many rounds passed, and how many cells are in the sample?
- 4 rounds, and 8 cells in the sample
- 4 rounds, and 5 cells in the sample
- 3 rounds, and 4 cells in the sample
- 5 rounds, and 5 cells in the sample
Use this
Notebook (model data), 4 rows. Columns: line, what it says. 1, A nerve cell and a muscle cell from one person carry the same DNA. 2, A muscle cell switches on the myosin gene, and a nerve cell leaves it off. 3, A nerve cell has lost the myosin gene, since it does not use it. 4, Two cells of equal size can still be different cell types.
Noah proofreads a notebook about genes. Exactly one line is wrong. Which line, and why?
- Line 2, since a nerve cell uses its whole set of genes
- Line 4, since equal size means equal cell type
- Line 3, since an unused gene stays in the DNA
- Line 1, since cells with different jobs have different DNA
Use this
Notebook (model data), 4 rows. Columns: line, what it says. 1, A stem cell can divide to make more stem cells. 2, Adults do not have stem cells, so bone marrow cannot make new blood cells. 3, Bone marrow stem cells make platelets, red blood cells and white blood cells. 4, Skin epithelial stem cells give rise to keratinocytes.
Pia proofreads a notebook about stem cells. Exactly one line is wrong. Which line, and why?
- Line 4, since skin stem cells give rise to blood cells
- Line 1, since stem cells are found in children but not adults
- Line 3, since a bone marrow stem cell can make any cell in the body
- Line 2, since adult bone marrow does hold stem cells
Tala writes: cells J and K are the same type because both are 10 µm wide. Does the card support this?
- Yes, both have a nucleus, so they are the same type
- No, J and K differ in shape and features, which show different types
- Yes, cells of equal width are the same type of cell
- No, J and K must carry different DNA, since they are different types
The front reads: stem cells from umbilical cord blood are multipotent. The back is blank. Zee writes: multipotent cord blood stem cells can give rise to a nerve cell, a skin cell and a muscle cell. Does the label support this?
- Yes, multipotent cells can give rise to any cell type
- Yes, young stem cells are more flexible than adult ones
- No, multipotent cells give rise to a limited range of related cell types
- No, a stem cell is already specialized, so it cannot give rise to other cells
Use this
Dividing cells in adults and plants (real data, from OpenStax Anatomy and Physiology 2e and Biology 2e), 3 rows. Columns: place, cells that keep dividing. adult bone marrow, hematopoietic stem cells. adult skin, epithelial stem cells. plant shoot and root tips, apical meristem cells, which act like stem cells: they keep dividing and give rise to specialized tissue.
Ari writes: stem cells are found in young animals, so adults and plants have none. Does the card support this?
- No, since the card lists cells that are already specialized
- Partly: adults have stem cells, but plants have no dividing cells
- Yes, stem cells are found in young animals and are lost with age
- No, the card lists stem cells in adults and dividing meristem cells in plants
