Meiosis and Chromosomal Abnormalities

Vocabulary-style flashcards covering terminology, stages, and genetic abnormalities associated with meiosis based on the provided lecture transcript.

Meiosis

A process of cell division that produces haploid cells from diploid cells, taking two cell cycles to complete.

Haploid

A cell containing $1$ copy of each chromosome ($n=23$ in humans).

Diploid

A cell containing $2$ copies of each chromosome ($2n=46$ in humans).

Gametes

Haploid sex cells (sperm and egg) produced by meiosis.

Zygote

A fertilized egg produced by two haploid cells (sperm and egg); zygotes are diploid.

Somatic cell

All diploid cells of the body except the gametes, containing $46$ chromosomes total organized into $23$ pairs.

Homologous chromosomes

A pair of chromosomes that code for the same genes.

Germ cell

A diploid cell that undergoes two divisions to begin the process of meiosis.

Synapsis

An event in Prophase 1 where homologous chromosomes pair up closely.

Chiasmata

The location where homologous chromosomes exchange genetic material during the process of crossing-over.

Crossing-over

The exchange of genetic material between non-sister chromatids of homologous chromosomes.

Tetrad

The structure formed when homologous chromosomes bind firmly together along their length during Prophase 1.

Kinetochore

The structure on centromeres where spindle fibers attach during pro-metaphase.

Nondisjunction

A failure in meiosis where chromosomes or chromatids do not separate correctly, leading to cells with missing or extra chromosomes.

Trisomy

A condition in which there are three chromosomes instead of a homologous pair of two.

Monosomy

A condition in which one chromosome is missing from a pair.

Karyogram

A visual representation of the $46$ chromosomes, or $23$ pairs of homologous chromosomes, numbered for identification.

Turner’s syndrome (XO)

A condition where a person has $45$ chromosomes; generally an infertile female who needs estrogen supplements.

Klinefelter’s syndrome (XXY)

A condition where a person has $47$ chromosomes; usually presents as an infertile male.

Jacob’s syndrome (XYY)

A condition where a person has $47$ chromosomes; usually a fertile male with increased height and overall size.

Triple X syndrome (XXX)

A condition where a person has $47$ chromosomes, carrying a small risk of atypical challenges.

Trisomy 21

Also known as Down’s syndrome; presents with features like a small skull, epicanthic folds, cognitive challenges, and early heart disease.

Trisomy 18

Edward’s syndrome; presents with a small head/jaw and pronounced cognitive challenges; life beyond $5-15$ days is rare.

Partial duplication

A chromosomal aberration involving extra genetic material that is duplicated on a chromosome.

Deletion

A chromosomal aberration where a portion of a chromosome is missing.

Inversion

A chromosomal aberration where a section of a chromosome is placed upside down.

Translocation

A chromosomal aberration where part of a chromosome is moved to another non-homologous chromosome.