Chromosomes, Cell Division, and Genetics

Vocabulary practice flashcards covering chromosome structure, the cell cycle, mitosis, meiosis, cancer biology, and chromosomal abnormalities.

Chromosome

A single, continuous molecule of DNA wrapped around proteins that carries genetic information.

Karyotype

A visual image of an individual's complete set of chromosomes, isolated from a cell and arranged in numerical order.

Homologous Chromosomes

Two chromosomes in a pair—one inherited from the mother and one from the father—that have the same length, shape, and genes for the same traits.

Sex Chromosomes

The final pair of chromosomes (Pair 23 in humans) that determine biological sex (XX for female, XY for male).

Autosomes

All the chromosomes that are not sex chromosomes (Pairs 1 through 22 in humans).

Haploid ($1n$)

A cell containing only one complete set of chromosomes, such as sperm or egg cells.

Diploid ($2n$)

A cell containing two complete sets of chromosomes, one set inherited from each parent, such as skin or muscle cells.

Histone

A specialized protein that eukaryotic DNA wraps around to compact and organize into chromatin and chromosomes.

Condensation

The process where loose DNA strands tightly wind and pack together into visible, distinct chromosomes.

Binary Fission

A type of simple, rapid asexual reproduction used by prokaryotes (bacteria) where a cell splits into two.

Somatic Cells

Body cells (such as skin or muscle) that are diploid ($2n$) and divide via mitosis.

Gametes

Mature haploid ($1n$) sex cells (sperm and egg) that are produced via meiosis.

Germ Cell

A diploid cell in the reproductive organs that undergoes meiosis to produce gametes.

Gonads

The reproductive organs (testes in males, ovaries in females) where gametes are produced.

Sister Chromatids

Two identical copies of a single replicated chromosome, joined together at the centromere.

Centromere

The constricted region of a chromosome where sister chromatids are held together and where spindle fibers attach.

Interphase

The longest part of the cell cycle where the cell grows, performs everyday functions, and copies its DNA.

$G_1$ Phase (Gap 1)

The first gap phase of interphase where the cell grows larger, copies organelles, and makes molecular building blocks.

$S$ Phase (Synthesis)

The synthesis phase of interphase where the cell replicates its DNA, creating a complete duplicate copy of its genome.

$G_2$ Phase (Gap 2)

The second gap phase of interphase where the cell grows more, makes proteins and organelles, and reorganizes contents in preparation for mitosis.

Mitosis

The process of nuclear division in eukaryotic cells that separates identical sets of chromosomes into two new nuclei.

Prophase

The first stage of mitosis where chromosomes condense, the nuclear envelope breaks down, and spindle fibers begin to form.

Metaphase

The stage of mitosis where chromosomes line up single-file down the middle (equator) of the cell.

Anaphase

The stage of mitosis where sister chromatids are pulled apart by spindle fibers toward opposite ends of the cell.

Telophase

The final stage of mitosis where nuclear membranes reform around the two new sets of chromosomes and chromosomes begin to uncoil.

Cytokinesis

The physical splitting of the cytoplasm, resulting in two distinct daughter cells.

Centriole

A barrel-shaped organelle that helps organize the spindle fibers during animal cell division.

Spindle Fiber

Protein microtubules that emerge during division to physically move and separate chromosomes.

DNA Helicase

An enzyme that unwinds and "unzips" the double-stranded DNA helix by breaking hydrogen bonds between base pairs.

DNA Polymerase

The key enzyme that builds a new DNA strand by matching free nucleotides to the exposed template strand.

Checkpoint

A critical control point in the cell cycle where stop and go signals regulate whether a cell can proceed to the next phase.

Meiosis

A specialized two-step nuclear division that reduces chromosome number by half to create genetically unique haploid gametes.

Crossing Over

The exchange of genetic material between non-sister chromatids of homologous pairs during Prophase 1, creating brand-new combinations of genes.

Fertilization

The fusion of a haploid sperm cell and a haploid egg cell.

Zygote

The initial diploid ($2n$) cell formed by the fusion of a sperm and an egg during fertilization.

Telomeres

Protective caps at the ends of chromosomes that shorten every time a cell divides, driving biological aging.

Cancer

A disease characterized by uncontrolled, rapid cell division due to a breakdown or failure in cell cycle checkpoints.

Benign Tumor

A non-cancerous mass of abnormal cells that stays clumped at its original site.

Malignant Tumor

A cancerous mass of cells that invades neighboring tissues and can spread.

Metastasis

The spread of cancer cells away from their original location to distant parts of the body via the bloodstream or lymph system.

Immunotherapy

A type of cancer treatment that boosts or trains the patient's own immune system to fight cancer cells.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate properly during meiosis, resulting in gametes with abnormal numbers of chromosomes.

Down Syndrome

A genetic disorder (Trisomy 21) caused by a nondisjunction event that leaves an individual with three copies of chromosome 21.