Cell Cycle, Mitosis, and Meiosis: Key Concepts for Biology

Anaphase

Sister chromatids separate and are pulled to opposite poles of the cell.

Benign

A noncancerous tumor that does not spread to other parts of the body.

Binary fission

A type of asexual reproduction in prokaryotes where one cell divides into two identical cells.

Cancer

A disease caused by uncontrolled cell division due to damaged genes regulating the cell cycle.

Cell cycle

The series of stages a cell goes through as it grows, prepares for division, and divides.

Centromere

The region of a chromosome where sister chromatids are attached.

Checkpoints

Control points in the cell cycle where the cell verifies if processes have been properly completed before moving on.

Chromatin

Uncoiled DNA and proteins found in the nucleus during interphase.

Chromosome

Tightly coiled DNA and proteins that contain genetic information.

Crossing over

Exchange of genetic material between homologous chromosomes during prophase I of meiosis; increases genetic diversity.

Cytokinesis

Division of the cytoplasm to form two separate daughter cells.

Diploid (2n)

A cell containing two sets of chromosomes, one from each parent.

G1, G2 and S phases

G1: Cell growth; S: DNA replication; G2: Preparation for mitosis.

Genome

All the genetic material in an organism.

Homologous chromosomes

Chromosome pairs with the same genes in the same order but possibly different alleles.

Independent assortment

Random distribution of maternal and paternal chromosomes during meiosis I.

Interphase

The phase of the cell cycle when the cell grows, performs its normal functions, and duplicates DNA.

Metaphase

Chromosomes line up at the cell's equator.

Metastasis

The spread of cancer cells to other parts of the body through the blood or lymphatic system.

Meiosis

Cell division that produces gametes (sex cells) with half the number of chromosomes.

Mitosis

Division of the nucleus that produces two identical diploid cells.

Spindle

Microtubule fibers that separate chromosomes during cell division.

Prometaphase

Nuclear membrane breaks down; spindle fibers attach to chromosomes.

Prophase

Chromatin condenses into chromosomes; spindle forms; nuclear envelope breaks down.

Sister chromatids

Identical copies of a chromosome connected by a centromere.

Telophase

Nuclear membranes reform around chromosomes at each pole; chromosomes uncoil.

Tumor suppressor gene

A gene that regulates cell division; when mutated, can lead to uncontrolled growth.

DNA replication

The process of making an identical copy of a cell's DNA.

DNA polymerase

Enzyme that synthesizes new DNA strands in the 5' → 3' direction.

DNA helicase

Enzyme that unwinds and separates the two DNA strands.

Proofreading

The process by which DNA polymerase checks and corrects errors during DNA replication.

Describe the chromosome(s) of prokaryotes.

Single, circular DNA molecule located in the cytoplasm; smaller than eukaryotic chromosomes.

Describe the chromosome(s) of eukaryotes.

Multiple, linear chromosomes found in the nucleus; larger and more complex.

What is the name of prokaryotic cell division?

Binary fission.

What are the two types of eukaryotic cell division?

Mitosis (for growth/repair) and meiosis (for gamete production).

What is the process used to make a complete copy of DNA called?

DNA replication.

What enzyme synthesizes DNA, and in what direction?

DNA polymerase; 5' to 3'.

What is the role of DNA helicase?

Unwinds and separates DNA strands during replication.

What is DNA proofreading and repair?

Correction of base-pairing errors by DNA polymerase to prevent mutations.

What happens during each phase of interphase?

G1: Growth; S: DNA replication; G2: Preparation for mitosis.

What happens during each phase of mitosis?

Prophase: Chromosomes form; Metaphase: Align in middle; Anaphase: Separate; Telophase: Nuclei form.

Do all cells divide continuously?

No, some (like nerve or muscle cells) exit the cycle and enter G₀ phase.

What is the cell cycle and what are checkpoints?

The sequence of growth and division; checkpoints ensure correct DNA replication and division.

What are the three main checkpoints and what do they check for?

G1: DNA integrity and cell size; G2: Correct DNA replication; M: Proper chromosome attachment to spindle.

What is the relationship between a genome, chromosome, and gene?

A genome is all genetic material; chromosomes are DNA structures; genes are DNA segments coding for traits.

What causes cancer? Mutations in what types of genes?

Mutations in oncogenes or tumor suppressor genes cause uncontrolled cell division.

What is the difference between a benign and malignant tumor?

Benign doesn't spread; malignant invades other tissues.

What is metastasis?

The spread of cancer cells to new sites through blood or lymph.

When is the chromosome number cut in half in meiosis?

During meiosis I.

Why is it important that chromosome number is cut in half during meiosis?

So that fertilization restores the correct diploid number.

What are the two processes that increase genetic diversity in meiosis?

Crossing over and independent assortment.