Unit 4A - Cell Cycle

Why is cell division essential for prokaryotic and eukaryotic life?: It allows organisms to reproduce, grow, repair damaged tissues, and replace old or dead cells to maintain proper functioning.

How do prokaryotes reproduce by binary fission?: The cell copies its DNA, grows, and splits into two identical daughter cells.

Steps of prokaryotic cell division:: Chromosome duplication and separation → Cell elongation and chromosome movement → Division into two daughter cells.

Steps of eukaryotic cell division (mitosis):: Interphase → Prophase → Metaphase → Anaphase → Telophase/Cytokinesis.

What happens during Interphase?: The cell grows, replicates centrioles and DNA, and prepares for division with loosely packed chromatin.

What happens during Prophase?: Chromatin condenses into chromosomes, centrioles move to poles, spindle forms, and nuclear envelope breaks down.

What happens during Metaphase?: Chromosomes line up at the equator; spindle fibers attach to the centromeres of sister chromatids.

What happens during Anaphase?: Chromatids separate and move to opposite poles as centromeres split and spindle fibers shorten.

What happens during Telophase and Cytokinesis?: Two nuclei form with identical chromosomes; spindle fibers break down and the cell splits.

What is a cleavage furrow?: The indentation in the cell membrane during animal cell cytokinesis where the cell will divide.

How are sister chromatids formed and what happens to them?: Formed during DNA replication, they stay connected at the centromere until anaphase, when they separate into daughter cells.

Four main stages of the cell cycle:: G₁ (cell growth), S (DNA replication), G₂ (prep for mitosis), M (mitosis and cytokinesis).

What controls the cell cycle?: Checkpoints, cyclins, and enzymes that verify accurate completion of each stage.

G1 checkpoint checks for:: DNA damage, enough nutrients, and proper cell size.

G2 checkpoint checks for:: Accurate DNA replication and repairs damage if needed.

M checkpoint checks for:: Chromosome alignment and spindle fiber attachment before division.

When is DNA replicated?: During the S phase of Interphase.

When are chromosomes sorted?: During Metaphase of Mitosis.

When are two new cells formed?: During Cytokinesis, following Mitosis.

How does cytokinesis differ in plant vs. animal cells?: Animal cells pinch inward forming a cleavage furrow; plant cells build a cell plate that becomes the cell wall.

Anchorage dependence:: Cells must be attached to a surface to divide.

Benign tumor:: A non-cancerous growth that does not spread.

Cancer:: Uncontrolled cell growth due to failed cell cycle control.

Density-dependent inhibition:: Crowded cells stop dividing.

Locus (loci):: A gene's specific location on a chromosome.

Malignant tumor:: A cancerous growth that can spread to other parts of the body.

Metastasis:: The spread of cancer cells from the original site to other areas.

Prometaphase:: Mitotic stage where the nuclear envelope breaks down and spindle fibers attach to chromosomes.

Tumor:: An abnormal mass of cells caused by uncontrolled cell division.