Grade 10 Mitosis Lecture Notes 2025

Question-and-answer flashcards covering chromosomes, DNA replication, the cell cycle, and the stages and events of mitosis.

What are chromosomes?

Thread-like structures found in the nucleus of almost all cells that carry hereditary information.

What is the main hereditary function of chromosomes?

They transfer genetic characteristics from one generation to the next.

What is chromatin?

The diffuse mass of DNA and proteins seen when a cell is not dividing.

How do chromosomes change appearance when a cell begins to divide?

The chromatin condenses into shorter, thicker, visible single-stranded chromosomes.

What two components make up each chromosome?

DNA helically wrapped around histone proteins.

What is a gene?

A specific segment of DNA on a chromosome that controls a particular hereditary characteristic.

What must happen to DNA before a cell divides?

All nuclear genetic material must be duplicated through DNA replication.

After DNA replication, what are the identical copies of a chromosome called?

Sister chromatids.

What structure joins two sister chromatids together?

The centromere.

Roughly how long does an average human cell cycle take to complete?

About 25 hours.

What type of cell division occurs in prokaryotes?

Binary fission.

Name the three main stages of the eukaryotic cell cycle.

Interphase, the mitotic (M) phase, and cytokinesis.

What happens during interphase?

The cell grows, accumulates nutrients, and replicates its DNA in preparation for division.

Which three sub-phases make up interphase?

G1 (growth/preparation for DNA synthesis), S (DNA replication), and G2 (final growth/preparation for mitosis).

Approximately how long does interphase last?

About 22 hours.

Give two examples of human cells that generally do NOT undergo mitosis.

Red blood cells and mature nerve cells (muscle cells are another acceptable example).

Define mitosis.

The process in which a single nucleus divides to form two identical daughter nuclei.

What is karyokinesis?

Division of the nucleus and chromosomes.

What is cytokinesis?

Division of the cytoplasm, organelles, and cell membrane following karyokinesis.

List the four phases of mitosis in order.

Prophase, Metaphase, Anaphase, Telophase.

State two key events of prophase.

Chromatin condenses into visible double-stranded chromosomes, and the nuclear membrane and nucleolus disappear (other events: centrioles move to poles; spindle forms).

What characterizes metaphase?

Replicated chromosomes align in a single row at the cell equator, and spindle fibres attach to their centromeres.

What happens during anaphase?

Sister chromatids separate and move to opposite poles as the cohesin holding them together breaks down; cytokinesis begins.

Describe two events of telophase.

Daughter chromosomes reach the poles and a new nuclear membrane and nucleolus form around each set (spindle disappears; cytokinesis completes).

How does cytokinesis differ in plant and animal cells?

Animal cells form a cleavage furrow that pinches the cell in two, while plant cells build a cell plate (transverse wall) at the equator.

Why is the equal separation of sister chromatids important?

It ensures that each daughter cell receives an identical set of chromosomes.

What structure guides chromosome movement during mitosis?

Spindle fibres composed of microtubules.

Which part of mitosis marks the completion of karyokinesis?

Telophase.