The Cell Cycle and Regulation

Flashcards covering the overview of cell division, stages of mitosis, cytokinesis, and the molecular regulation and malfunctions of the cell cycle.

What are the three primary roles of cell division in multicellular organisms?

Reproduction, growth and development, and tissue renewal (replacement of dying cells).

What is the process of cell division used by bacteria like $E. coli$ called?

Binary fission.

In eukaryotic cell division, what are the two main types and their general outcomes?

Meiosis occurs in gamete production resulting in unique haploid ($n$) cells, and Mitosis occurs in somatic cells resulting in identical diploid ($2n$) cells.

What is chromatin?

DNA associated with histone proteins, which can exist in a condensed or uncondensed state.

What is the specific diploid ($2n$) and haploid ($n$) chromosome number for humans?

The diploid number is $2n = 46$ and the haploid number is $n = 23$.

How are sister chromatids connected prior to separation?

They are connected via cohesin proteins at the centromere region.

Which phase of the cell cycle is dedicated to the replication of genetic material (DNA Synthesis)?

S phase.

What occurs during the $G_1$ phase of the cell cycle?

The cell grows in size and prepares for DNA replication by producing proteins; non-dividing cells may be arrested here in a state called $G_0$.

What happens during the Prophase stage of mitosis?

Duplicated chromosomes condense, the mitotic spindle begins to form, nucleoli disappear, and centrosomes move toward opposite poles.

What is the characteristic arrangement of chromosomes during Metaphase?

Duplicated chromosomes align along the imaginary metaphase plate of the cell while centrosomes are at opposite poles.

What occurs during Anaphase to ensure sister chromatids separate?

Cohesins connecting the sister chromatids are cleaved, allowing microtubules to mediate their separation toward opposite poles.

What is the kinetochore?

A structure of DNA and proteins located in the centromere where spindle microtubules attach to the chromosome.

How does cytokinesis differ between animal and plant cells?

In animal cells, actin microfilaments and motor proteins form a contractile ring that creates a cleavage furrow; in plant cells, vesicles transport wall material to form a cell plate which becomes a new cell wall.

What two types of proteins internally control the cell cycle?

Cyclins and Cyclin Dependent Kinases (CDKs).

What is Maturation Promoting Factor (MPF)?

A complex of cyclin protein and CDK that mediates the passage of a cell from the $G_2$ phase into the M phase.

According to cell fusion experiments, what happens when a cell in $G_1$ is fused with a cell in the S phase?

The $G_1$ nucleus immediately enters the S phase and begins DNA synthesis.

What is the function of the $G_1$ checkpoint?

It is a key checkpoint that determines if a cell remains in $G_0$ or commits to dividing by entering the cell cycle.

What is the 'multi-hit' hypothesis in relation to cancer?

The idea that mutations in multiple genes, rather than just one mutant gene, are typically necessary for a cell to become cancerous and proliferate.

What is the definition of metastasis?

The spread of cancer cells from the original tumor to other locations in the body.

What is the difference between tumor-suppressor genes and oncogenes?

Tumor-suppressor genes (like $p53$ and $BRCA1$) normally inhibit the cell cycle and repair DNA, while oncogenes are mutated proto-oncogenes that abnormally stimulate the cell cycle.