Cell Division, Life Cycles, and Chromosomal Variations

Vocabulary flashcards covering cellular division, stages of meiosis and mitosis, sexual and asexual life cycles, chromosomal morphology, structural mutations, and numerical chromosomal variations such as aneuploidy and polyploidy.

Reductive Division

The type of cell division that occurs during meiosis where the chromosome number is halved, transitioning a cell from diploid ($2n$) to haploid ($1n$).

Crossing Over

The exchange or swapping of genetic material between homologous chromosomes that occurs during prophase I of meiosis I following bivalent (tetrad) formation.

Anaphase I

The specific stage of meiosis I during which homologous chromosomes separate and move toward opposite poles of the cell.

Anaphase II

The stage of meiosis II during which sister chromatids are separated in a haploid cell.

Asexual Reproduction

A form of reproduction involving only one parent that produces genetically identical offspring (clones) via mitotic divisions without the formation or fusion of gametes.

Sexual Reproduction

A form of reproduction involving two parents in which haploid gametes produced by meiosis fuse to create a genetically unique diploid zygote.

Gene

A sequence within DNA that codes for specific characteristics and traits, passed along from generation to generation.

Diploid-Dominant Life Cycle

A sexual life cycle where the multicellular organism is diploid for the majority of its lifespan (common in most animals), and the only haploid stage consists of specialized gametes.

Haploid-Dominant Life Cycle

A sexual life cycle typical of fungi where the multicellular organism is haploid and produces spores; the brief diploid zygote immediately undergoes meiosis to regenerate haploid spores.

Alternation of Generations

A sexual life cycle common in plants and some algae that alternates between a multicellular diploid generation and a multicellular haploid generation.

Sporophyte

The multicellular diploid ($2n$) organism in an alternation of generations life cycle that produces haploid spores through meiosis.

Gametophyte

The multicellular haploid ($1n$) organism in an alternation of generations life cycle that produces haploid gametes through mitosis.

Wild Type

The most common or normally seen characteristic, chromosomal structure, or chromosomal number observed in nature for a given species.

Metacentric

A chromosome structure where the centromere is positioned right in the middle.

Submetacentric

A chromosome structure where the centromere is located slightly off-center.

Acrocentric

A chromosome structure where the centromere is located near one end of the chromosome.

Cumulocentric

A chromosome structure where the centromere is positioned at the very end of the chromosome.

$p$ Arm and $q$ Arm

The structural designation of chromosome arms in a karyotype, where $p$ (petite) denotes the shorter arm arranged at the top, and $q$ denotes the longer arm arranged at the bottom.

Giasma Stain

A specialized staining dye that binds to adenine and thymine base pairs, producing distinct dark purple banding patterns useful for identifying chromosomes and detecting mutations.

Mutation

A heritable change in genetic material that can be passed down to subsequent cell generations or offspring.

Chromosomal Deletion

A structural mutation characterized by the loss or absence of a segment of genetic material, reducing the overall length of the chromosome.

Chromosomal Duplication

A structural mutation where a segment of genetic material is replicated, resulting in extra copies and an increase in total genetic material.

Chromosomal Inversion

A structural mutation in which a segment of DNA is flipped or inverted in orientation, altering the order of genetic material without changing the total amount.

Simple Translocation

A chromosomal alteration where a piece of one chromosome breaks off and attaches to a different non-homologous chromosome.

Reciprocal Translocation

A chromosomal alteration where two non-homologous chromosomes mutually exchange or swap segments of genetic material with each other.

Euploid

An organism or cell possessing an exact multiple of the complete chromosome set, such as haploid ($1n$) or diploid ($2n$).

Polyploidy

A chromosomal variation in which an organism possesses more than two complete sets of chromosomes, such as triploid ($3n$) or tetraploid ($4n$).

Aneuploidy

A chromosomal condition in which the number of chromosomes is abnormal due to an extra or missing chromosome in a specific set.

Monosomy

An aneuploid state represented as $2n - 1$, where an individual is missing one chromosome from a homologous pair.

Trisomy

An aneuploid state represented as $2n + 1$, where an individual possesses three copies of a specific chromosome instead of the normal two.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate properly during cell division (mitosis or meiosis), producing daughter cells with abnormal chromosome numbers.

Autosomes

Non-sex chromosomes; in humans, there are 22 pairs (22 distinct types) present in somatic cells.

Turner Syndrome

A human sex-chromosome monosomy condition characterized by the presence of only a single $X$ chromosome.

Triple X Syndrome

A human sex-chromosome trisomy condition where an individual possesses three $X$ chromosomes instead of two.

Trisomy 21

A viable autosomal trisomy condition in humans characterized by having one extra copy of chromosome 21 ($2n + 1$).