GTS 161 - Chromosomes and Cellular Reproduction - Vocabulary Flashcards

Vocabulary flashcards covering key terms from Chapter 2 (Lectures 1.1–1.4) about chromosomes and cellular reproduction.

Chromosome

A linear molecule of DNA wrapped around histone proteins (forming chromatin) that carries genes; in eukaryotes it resides in the nucleus and can be replicated into sister chromatids.

Chromatid

One of the two identical copies of a replicated chromosome that are held together at the centromere.

Sister chromatids

The pair of identical chromatids formed after DNA replication, joined at the centromere until they separate during mitosis or meiosis II.

Chromatin

The complex of DNA and histone proteins that forms chromosomes and regulates DNA accessibility; condenses to form chromosomes during cell division.

Centromere

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

Telomere

The protective cap at the ends of linear chromosomes that prevents degradation and fusion.

Origin of replication

DNA sequence where DNA replication initiates.

Histone

Protein around which DNA winds to form nucleosomes, providing the structure of chromatin.

Nucleus

Membrane-bound organelle in eukaryotic cells that houses the genome.

DNA

Deoxyribonucleic acid; the molecule that stores genetic information.

Gene

A DNA sequence that encodes a product, typically a functional RNA or protein.

Locus

The specific location of a gene on a chromosome.

Allele

An alternative form of a gene that can result in different traits.

Homozygous

Having two identical alleles at a given gene locus.

Heterozygous

Having two different alleles at a given gene locus.

Diploid (2n)

Two complete sets of chromosomes, typically one from each parent; homologous chromosome pairs present.

Haploid (n)

One complete set of chromosomes; gametes contain n chromosomes.

Homologous chromosomes

Chromosomes that are the same size and carry the same genes in the same order, though they may carry different alleles.

Chromosome number

The total number of chromosomes in a somatic cell (e.g., 2n = 46 in humans).

Chromosome set

The entire collection of chromosomes in a genome (diploid set 2n or haploid set n).

Chromosome morphology

Classification of chromosome shape based on centromere position.

Metacentric

Chromosome with centromere near the middle; arms of roughly equal length.

Submetacentric

Centromere off-center; one arm longer than the other.

Acrocentric

Centromere near the end; very short p-arm.

Telocentric

Centromere at the very end of the chromosome (conceptual; not typical in humans).

Prokaryote

Organism without a nucleus or membrane-bound organelles; primarily bacteria/archaea; usually unicellular.

Eukaryote

Organism with a nucleus and membrane-bound organelles; linear chromosomes.

Mitosis

Nuclear division yielding two genetically identical diploid daughter cells; part of somatic cell cycle.

Meiosis

Two-stage division producing four haploid gametes; generates genetic variation via crossing over and independent assortment.

Gamete

A haploid reproductive cell (sperm or egg).

Zygote

Diploid cell formed by fertilization of two gametes.

Recombination

Genetic exchange that creates new allele combinations; includes crossing over and independent assortment.

Crossing over

Exchange of segments between nonsister chromatids of homologous chromosomes during prophase I, creating recombinant chromatids.

Independent assortment

Random orientation and separation of homologous chromosome pairs during meiosis I, generating genetic variation.

Synapsis

Pairing of homologous chromosomes during prophase I to form a tetrad (bivalent).

Tetrad / Bivalent

Paired homologous chromosomes formed during synapsis, consisting of four chromatids.

Chiasma

Visible site of crossing over between nonsister chromatids during meiosis I.

Interkinesis

Brief interphase-like period between meiosis I and II with no DNA replication.

Cohesin

Protein complex that holds sister chromatids together; cleaved to allow separation; different forms in mitosis vs meiosis.

Shugoshin

Protein that protects centromeric cohesin during meiosis I, preventing premature separation of sister chromatids.

Anaphase II

Stage in meiosis II where sister chromatids separate and migrate to opposite poles.

Prophase I

First stage of meiosis I; chromosomes condense, synapsis occurs, crossing over.

Metaphase I

Homologous chromosome pairs align on the metaphase plate during Meiosis I.

Anaphase I

Homologous chromosomes separate and move to opposite poles during Meiosis I.

Telophase I

Chromosomes arrive at poles; cytoplasm divides; two haploid daughter cells formed.

Interphase

Cell-cycle stage consisting of G1, S, G2; DNA replication occurs in S phase.

G1 phase

Cell growth and preparation for DNA synthesis; checkpoint before S phase.

S phase

DNA synthesis phase; replication of chromosomes.

G2 phase

Cell prepares for mitosis; checkpoint before M phase.

Checkpoints

Control points (G1/S, G2/M, spindle assembly) that ensure proper progression through the cell cycle.

Spindle apparatus

Microtubule-based structure that separates chromosomes during cell division.

Centrosome

Organizing center for spindle microtubules.

Cytokinesis

Cytoplasmic division that completes cell division, producing two daughter cells.

Genome

The complete set of genetic material present in an organism or cell.