Body cells divide in a cell cycle. First the cell grows, makes more ribosomes and mitochondria, and copies its DNA so each chromosome has two identical halves. In mitosis, one set of chromosomes is pulled to each end of the cell, and the nucleus divides. Finally the cytoplasm and membrane divide, making two genetically identical daughter cells. Mitosis is used for growth, repair and asexual reproduction.
Stem cells are unspecialised cells that can divide and become many types of cell. Embryonic stem cells can become almost any cell; adult stem cells in bone marrow can form only some types. In plants, meristems at shoot and root tips make new cells all their lives. Stem cells may treat diseases such as diabetes, but there are ethical concerns and risks such as infection.
Worked example
A cell with 46 chromosomes divides by mitosis. How many chromosomes are in each daughter cell?
- The DNA is copied before division.
- Each daughter cell gets one full set.
Answer:Each daughter cell has 46 chromosomes.
Key words
- mitosis
- division making two identical cells
- cell cycle
- growth, DNA copying and division
- stem cell
- unspecialised cell that can become other types
- meristem
- plant tissue with stem cells
New questions every time.
NGSS-referenced: HS-LS1-4