🧬 Human Cell Biology

What are the phases of the cell cycle?

G₁, S, G₂ and M phases.

What happens during S phase?

DNA is replicated, so each chromosome consists of two sister chromatids.

What is interphase?

G₁ + S + G₂.

What are the two major processes of M phase?

Mitosis (karyokinesis) and cytokinesis.

What is mitosis?

Cell division that produces two daughter cells with the same genetic component as the parent cell.

What are the five stages of mitosis?

Prophase → Prometaphase → Metaphase → Anaphase → Telophase.

What happens during prophase?

Chromosomes condense, centrosomes move to opposite poles, and the mitotic spindle forms.

What is the metaphase plate?

The equatorial region of the spindle where chromosomes align.

What is a kinetochore?

A structure associated with the centromere to which spindle fibres attach.

What happens during anaphase of mitosis?

Centromeres divide and sister chromatids separate toward opposite poles.

What happens during telophase?

Nuclear membranes reform, chromosomes uncoil, and spindle fibres disappear.

What is cytokinesis?

Division of the cytoplasm to form two daughter cells.

What is the main purpose of meiosis?

Production of haploid sex cells/gametes from diploid cells.

How many DNA replications occur during meiosis?

One DNA replication followed by two divisions.

What does Meiosis I separate?

Homologous chromosomes.

Why is Meiosis I called reduction division?

It reduces the chromosome number from diploid to haploid.

What are the five stages of Prophase I?

Leptotene → Zygotene → Pachytene → Diplotene → Diakinesis.

What happens during zygotene?

Homologous chromosomes pair by synapsis to form bivalents/tetrads.

What happens during pachytene?

Crossing over occurs between homologous chromosomes.

What are chiasmata?

Points where homologous chromosomes remain attached following crossing over.

What happens during diplotene?

Homologous chromosomes begin separating but remain attached at chiasmata.

What happens during metaphase I?

Homologous chromosome pairs align at the metaphase plate.

What happens during anaphase I?

Homologous chromosomes separate and move to opposite poles.

What does Meiosis II separate?

Sister chromatids.

What are the major sources of genetic variation in meiosis?

Crossing over and random assortment of chromosomes.

What is hyperplasia?

Increased production and growth of normal cells due to increased cell division.

What is hypertrophy?

Enlargement of individual cells, resulting in increased tissue or organ size.

What is metaplasia?

Replacement of normal tissue cells by an abnormal cell form in response to stress, injury or infection.

What is neoplasia?

Abnormal new development of cells that may be benign or malignant.

What is the difference between benign and malignant growth?

→ Benign: remains localized and does not spread.
→ Malignant: can spread to other parts of the body; this spread is called metastasis.