Cell division and stem cells

DNA

Deoxyribonucleic acid, found inside the nucleus of eukaryotic cells.

DNA organization in eukaryotic cells

DNA is arranged in long strands, wrapped into structures called chromosomes.

Gene

A section of DNA that acts as a code to build a protein.

Chromosome

Carries many genes, with instructions for different proteins.

Need for new cells in multicellular organisms

For growth, repair, and replacement of old/damaged cells.

Mitosis

A type of cell division that produces two identical daughter cells for growth and repair.

Cell cycle

A repeating process in which cells grow, replicate their DNA, and divide.

Speed of cell cycle

Different cells complete the cycle at different speeds (e.g., skin cells regenerate quickly).

Short life cycle of some cells

Because they wear away quickly (e.g., skin cells) and need regular replacement.

Stages of mitosis

Prophase → Metaphase → Anaphase → Telophase → Cytokinesis.

Prophase

Chromosomes condense, nuclear membrane breaks down, and spindle fibers form.

Metaphase

Chromosomes align in the middle of the cell.

Anaphase

Sister chromatids are pulled apart toward opposite sides of the cell.

Telophase

Two new nuclei form, and chromosomes begin to uncoil.

Cytokinesis

The cytoplasm fully splits, producing two identical daughter cells.

Importance of mitosis order

It ensures accurate DNA distribution, preventing genetic errors.

Mitosis contribution to growth

Produces more genetically identical cells, increasing tissue size.

Mitosis in repair

Damaged tissues can regenerate by replacing old cells with new identical ones.

Difference between mitosis and meiosis

Mitosis produces identical cells, whereas meiosis produces gametes with genetic variation.

Preparation for mitosis

By replicating their DNA and building new organelles during interphase.

Uncontrolled mitosis

It can lead to tumor formation and cancer due to excessive cell division.

Interphase

The cell grows, makes proteins, and replicates its DNA.

Role of spindle fibers in mitosis

They attach to chromosomes and pull them apart during anaphase.

Chromosomes

They attach to chromosomes and pull them apart during anaphase.

Nuclear membrane breakdown in prophase

To allow chromosomes to move freely for division.

Cytoplasm in cytokinesis

It splits, separating the two daughter cells.

Cytokinesis in plant and animal cells

Animal cells pinch apart, while plant cells form a cell plate that becomes the new wall.

Mitosis producing identical cells

To ensure consistency in genetic information and function.

Number of chromosomes during mitosis

The number stays the same—each daughter cell receives an identical copy of DNA.

Differentiation

The process of cells becoming specialized for particular roles.

Zygote

A fertilized egg cell—the first cell in a developing organism.

Development of zygotes

They divide by mitosis to form an embryo (a ball of unspecialized cells).

Stem cells

Unspecialized cells that divide indefinitely and can become different types of cells.

Embryonic stem cells

Found in early-stage embryos, before cells differentiate.

Capabilities of embryonic stem cells

Give rise to any specialized cell in the body.

Adult stem cells

Yes, but adult stem cells can only become a limited number of cell types.

Location of adult stem cells

In bone marrow, skin, and some organs.

Medical uses of stem cells

They can treat diseases like leukemia and repair damaged tissues.

Importance of stem cells for research

They help scientists study cell growth, regeneration, and potential cures.

Ethical concerns about stem cell research

Some people object to using embryonic stem cells, as it involves the destruction of embryos.

Stem cells in plants

Yes, found in meristems (shoot and root tips).

Use of stem cells in plants

To continuously grow and produce new specialized cells.

Retention of stem cells in plants

They can regenerate and grow new parts unlike animal cells.

Stem cells in regenerative medicine

They can replace damaged or lost cells in conditions like spinal injuries.

Importance of stem cell research for genetic diseases

It allows scientists to study inherited disorders and develop treatments.

Obtaining embryonic stem cells

From unused embryos in fertility treatments.

Limitations of adult stem cells

They can only turn into certain cell types, unlike embryonic stem cells.

Controlling stem cell differentiation

By using chemical signals that direct them to become specific cell types.

Hope for organ repair with stem cells

They could be used to grow replacement tissues for damaged organs.