D2.1 Cell and Nuclear Division

What is the process by which new cells are generated in living organisms?

Cell division, often through mitosis and cytokinesis.

How do animal cells split the cytoplasm during cell division?

A ring of contractile actin and myosin proteins pinches the cell membrane.

What is the outcome of unequal division of cytoplasm during oogenesis in humans?

One cell receives almost all the cytoplasm, while the other receives very little.

What is the primary role of mitosis in eukaryotes?

To maintain the chromosome number and genome of cells.

What must occur before mitosis and meiosis?

DNA replication.

What are chromatids?

Two elongated DNA molecules held together after DNA replication.

What is a shared feature between meiosis and mitosis regarding DNA movement?

Both processes involve supercoiling of DNA and the use of microtubules to move chromosomes.

What is the first phase of mitosis?

Prophase.

What happens during metaphase of mitosis?

Chromosomes line up at the equator.

What does the term 'diploid' mean?

Having two sets of each chromosome (2n).

What does 'haploid' refer to?

Having one set of chromosomes.

What is non-disjunction?

The failure of chromosomes or chromatids to separate correctly during cell division.

How does Down syndrome occur?

It can result from non-disjunction leading to an extra chromosome 21 (trisomy 21).

What is the significance of crossing over in meiosis?

It creates genetic diversity by leading to new combinations of alleles.

What is cell proliferation?

The process of making more cells used for growth and tissue repair.

What stages make up the interphase of the cell cycle?

G1, S, and G2 phases.

What do cyclins do in the cell cycle?

They control the movement through different phases by regulating checkpoints.

How can mutations in genes that control the cell cycle lead to cancer?

They can convert proto-oncogenes to oncogenes or disable tumor suppressor genes, leading to uncontrolled cell division.

What is the difference between benign and malignant tumors?

Benign tumors are usually not harmful and do not spread, while malignant tumors can invade other tissues and spread.

What is the mitotic index?

The ratio of cells in mitosis to the total number of cells, indicating the level of cell division.