Lecture 10: Cell Cycle

What does cell theory state

All organisms consist of one or more cells, cells are life's basic units, and all cells come from existing cells.

What is the main function of cell division

To distribute genetic material into daughter cells.

Why do unicellular organisms divide

Reproduction.

Why do multicellular organisms divide

Growth, development, and repair.

What is a genome

A cell's total genetic material.

How is DNA usually organized in prokaryotes

One circular DNA molecule.

What is a chromosome

A DNA molecule associated with proteins.

What is chromatin

DNA and protein in a dispersed, less-condensed state.

When does chromatin condense into visible chromosomes

During cell division.

What does haploid (n) mean

One complete set of chromosomes.

What cells are typically haploid

Gametes.

What does diploid (2n) mean

Two complete sets of chromosomes.

What are homologous chromosomes

A pair with the same genes, length, and structural features.

Are human somatic cells haploid or diploid

Diploid.

Can haploid cells undergo mitosis

Yes; both haploid and diploid cells can undergo mitosis.

How do prokaryotes usually divide

Binary fission.

What is interphase

The period between cell divisions when growth and metabolism occur.

What percentage of the cell cycle is typically interphase

At least 90%.

What are the three stages of interphase

G1, S, and G2.

What happens during G1

Growth, development, and normal cell functions.

What happens during S phase

DNA replication.

Does DNA replication during S phase change ploidy

No; it doubles DNA amount, not chromosome sets.

What are sister chromatids

Identical copies of a replicated chromosome.

Where are sister chromatids joined

At the centromere.

What happens during G2

Metabolic activity and preparation for mitosis.

What two processes make up M phase

Mitosis and cytokinesis.

What is mitosis

Division of the nucleus to produce genetically identical nuclei.

What are the four stages of mitosis in order

Prophase, metaphase, anaphase, telophase.

What happens during prophase

Chromatin condenses, nuclear envelope breaks down, and spindle forms.

What is the mitotic spindle's function

Guide chromosome movement toward opposite cell poles.

What happens during metaphase

Chromosomes align at the metaphase plate.

Is the metaphase plate a physical structure

No; it is a location in the cell.

What happens during anaphase

Sister chromatids separate and move to opposite poles.

What are kinetochores

Protein structures attached to centromeres that participate in chromatid movement.

What is a separated sister chromatid called

An individual chromosome.

What happens during telophase

Chromosomes decondense and nuclear envelopes reform.

What is the genetic outcome of mitosis

Daughter nuclei genetically identical to the parent nucleus, barring mutations.

What is cytokinesis

Division of the cytoplasm to form two daughter cells.

Is cytokinesis the same process as mitosis

No; it is separate but usually overlaps with telophase.

How does cytokinesis occur in animal cells

A cleavage furrow pinches the cell in two.

What is a cleavage furrow

The inward pinching region of an animal cell during cytokinesis.

How does cytokinesis occur in plant cells

A cell plate forms and separates the daughter cells.