Chapter 8: DNA Replication, Binary Fission, and Mitosis

This set covers vocabulary and core concepts from Lecture 10, including DNA organization, human karyotypes, the stages of the cell cycle and mitosis, prokaryotic binary fission, and the mechanics of cancer and cell cycle regulation.

Gene

The fundamental physical and functional unit of heredity that contains instructions for building RNA and protein.

Genome

The complete DNA sequence for an individual, consisting of approximately $3 \times 10^9$ base pairs, around $20,000$ genes, and coding for about $100,000$ different proteins.

Karyotype

Refers to the number and size of chromosomes; typically humans have $23$ pairs.

Autosome

Non-sex chromosomes; in humans, there are $22$ autosomal pairs where changes affect males and females equally.

Sex chromosomes

The pair of chromosomes (XX for biological female, XY for biological male) that determine biological sex.

Down syndrome

A genetic condition characterized by a karyotype with $48$ chromosomes due to an extra chromosome $21$, resulting in distinct physical and cognitive traits.

de la Chapelle syndrome

A genetic condition where individuals with $46$ chromosomes and XX chromosomes develop as male due to the presence of the SRY (sex-determining) gene.

Gene expression

The process where information encoded in a specific region of DNA is transcribed and then translated into protein, allowing cells with the same genome to perform tissue-specific roles.

Apoptosis

Programmed cell death that removes old, unnecessary, or damaged cells without causing inflammation to surrounding tissue.

Interphase

The phase of the cell cycle where the cell grows and copies its DNA, consisting of the G1, S, and G2 sub-phases.

S phase

The part of interphase where DNA synthesis (replication) occurs.

G0 phase

A resting state in the cell cycle where the cell performs its normal functions and is not preparing to divide.

Origins of Replication

Multiple regions along the DNA where the replication process begins.

Helicase

The enzyme that unzips DNA by breaking hydrogen bonds, producing a replication fork.

DNA polymerase

The enzyme that assembles and proofreads new DNA strands during replication.

Binary fission

The process of cell division in unicellular prokaryotes (Bacteria and Archaea) that yields genetically identical cells.

Horizontal gene transfer

The transfer of genes between organisms that is not from parent to offspring.

Transformation

A type of horizontal gene transfer involving the direct uptake of free DNA from the environment.

Conjugation

A type of horizontal gene transfer involving direct contact between two cells to transfer genetic material via a sex pilus.

Transduction

A type of horizontal gene transfer where foreign DNA is introduced to a cell by a viral vector or virus.

Chromatin

A complex of DNA and histones (proteins) that forms nucleosomes.

Chromosome

The most condensed form of chromatin, organized to protect DNA from tangling or breaking during cell division.

Homologous chromosomes

Pairs of chromosomes that contain the same genes, consisting of one maternal set and one paternal set.

Sister chromatids

Two identical copies of duplicated DNA attached to each other via a centromere.

Microtubules

Protein tubes made by the centrosome that form mitotic spindles used to organize and separate sister chromatids.

Prophase

The stage of mitosis where DNA condenses into chromosomes, the nuclear membrane disintegrates, and centrosomes move to the poles to synthesize microtubules.

Metaphase

The stage of mitosis where chromosomes line up along the equator (metaphase plate) and microtubules attach to sister chromatids.

Anaphase

The stage of mitosis where sister chromatids are pulled apart by the mitotic spindle and the cell elongates.

Telophase

The stage of mitosis where chromosomes de-condense, nuclear membranes reform, and microtubules begin to disintegrate.

Cytokinesis

The division of the cytoplasm into two cells; in animals, this is mediated by protein filaments forming a contractile ring/cleavage furrow.

Cell plate

The structure formed from vesicles during cytokinesis in plant cells to create new cell walls.

Metastasis

The spread of cancer cells from one location in the body to another.

Tumor

A mass of cells resulting from uncontrolled cell division.

Benign tumor

A mass of cells contained within a capsule of connective tissue that prevents the tumor from spreading.

Malignant tumor

A mass of cancer cells that can "seed" new tumors throughout the body via the blood or lymph vessels.