Meiosis and Genetic Variation

A complete set of vocabulary flashcards covering the stages of meiosis, chromosomal division, genetic variation mechanisms, and common chromosomal errors based on Chapter 10.

Meiosis

A process of sexual reproduction involving the creation of Germ Cells or Gametes through reductive division to reduce paired chromosomes to single chromosomes.

Asexual Reproduction

A process (Mitosis) used by prokaryotes, protists, and for the replication of somatic cells to create $2$ identical daughter cells.

Zygote

A fertilized egg created by the union of $2$ Germ Cells (Sperm and Egg), containing a complete pair of chromosomes ($46$ chromosomes in $23$ pairs).

Germ Cell

A gamete, such as a sperm or egg, containing $1$ set of $23$ non-paired chromosomes ($n$).

Diploid ($2n$)

A cell containing $2$ full sets of chromosomes ($46$ chromosomes in humans) arranged in $23$ homologous pairs.

Haploid ($n$)

A cell containing a single set of non-paired chromosomes ($23$ chromosomes in humans).

Homologous Chromosomes

A set of chromosomes derived from $1$ maternal and $1$ paternal source that have the same genes in the same loci, but may have different alleles.

Gene

The basic unit of heredity that is transcribed to produce RNA.

Loci

A fixed position on a chromosome, defined by a gene or marker.

Allele

A variant in sequence, which can be a single polymorphism (substitution) or large insertions and deletions.

Meiosis I

The first stage of meiosis, known as reductive or reductional division, which involves the division of entire chromosomes (Diploid to Haploid).

Meiosis II

The second stage of meiosis involving the division of sister chromatids, mirroring the process of Mitosis.

Tetrad

Structure formed in Prophase I when $2$ homologous chromosome pairs bind firmly together along their length, consisting of $4$ sister chromatids.

Crossing Over

The process where non-sister chromatid arms swap segments of chromosomes randomly during Prophase I to increase genetic variation.

Chiasmata

The points of crossing where non-sister chromatids swap segments during Prophase I.

Independent Assortment

The random alignment and assembly of homologous chromosome pairs at the metaphase plate during Metaphase I.

Sister Chromatids

Identical copies of a chromosome held together at the centromere until they are separated during Anaphase II or Mitosis.

Aneuploidy

Errors in chromosome number resulting in too much or too little of a gene, which impacts protein expression levels.

Nondisjunction

An error in disjoining or separating chromosomes in Meiosis I or sister chromatids in Meiosis II.

Monosomy

A condition of having only $1$ chromosome of a pair; full autosomal monosomies are typically lethal.

Trisomy

A condition of having $3$ chromosomes of a pair; trisomies of small chromosomes like $13$, $15$, $18$, $21$, or $22$ are sometimes survival-compatible.

Turner Syndrome

A sex chromosome aneuploidy characterized by have an $X0$ genotype.

Klinefelter Syndrome

A sex chromosome aneuploidy characterized by an $XXY$ genotype.

Swyer Syndrome

A condition involving an $XY$ genotype with a female phenotype due to the translocation or dysregulation of the SRY gene.

X Inactivation

A process where excess $X$ chromosomes are randomly silenced through condensation into chromatin using special Xist RNA.

Inversions

Simple chromosomal rearrangements resulting from crossing-over errors.

Translocations

The movement of a large segment of a chromosome to a non-homologous chromosome, which can interrupt regulatory sequences.

Spermatocyte

A male gamete specialized for movement and delivery of the genome.

Oocyte

A female gamete characterized by specialized division of cytoplasm to provide organelles, nutrients, and space for a zygote.

SRY Gene

A gene on the $Y$ chromosome that triggers a transcription cascade causing the genital ridge to differentiate into Leydig and Sertoli cells.

Intersex

A term describing anatomy that is not textbook male or female, which can result from various chromosomal or regulatory errors.