Patterns of Chromosome Inheritance

Vocabulary practice flashcards covering chromosome structure, the cell cycle and checkpoints, mitosis, meiosis, gametogenesis, chromosomal abnormalities, and structural mutations based on Sylvia Mader's Human Biology Chapter 19.

Homologous Chromosomes (Homologues)

Pairs of chromosomes in a cell's nucleus; humans possess $46$ chromosomes arranged in $23$ pairs.

Autosomes

The $22$ pairs of human chromosomes that control traits unrelated to biological gender.

Sex Chromosomes

The single pair of chromosomes that contains genes controlling biological gender ($XY$ in males and $XX$ in females).

Diploid ($2n$)

Somatic (body) cells that contain paired chromosomes, totaling $46$ chromosomes in humans.

Haploid ($n$)

Sex cells or gametes containing only $23$ unpaired chromosomes.

Karyotype

The number and appearance of chromosomes in the nucleus of a eukaryotic cell, sorted by size and shape on a computer.

Karyogram

An arranged display of photomicrographs where all chromosomes of a cell have been identified and paired.

Colchicine

An anti-mitotic reagent used in karyotyping procedures to stop cell division during mitosis so metaphase chromosomes can be examined.

Interphase

The longest period of the cell cycle, divided into the $G_1$, $S$, and $G_2$ stages.

$G_1$ Stage

The phase of interphase in which the cell doubles its organelles and grows in size.

$S$ Stage

The stage of interphase during which DNA synthesis (replication) occurs.

$G_2$ Stage

The stage of interphase where proteins needed for division are synthesized and final preparations for cell division occur.

Mitosis

A process of nuclear division in somatic cells where one diploid ($2n$) cell produces two genetically identical diploid ($2n$) cells for growth and repair.

Cytokinesis

The division of the cell's cytoplasm that follows nuclear division.

$G_1$ Checkpoint

The main cell cycle checkpoint where growth signals, nutrients, and DNA integrity are evaluated; passing commits the cell to divide, while failure may send the cell to $G_0$ or trigger apoptosis.

$G_0$ Phase

A non-dividing state in which a cell remains alive and metabolically active without continuing through the cell cycle.

p53 Protein

A checkpoint protein that halts the cell cycle to repair damaged DNA at the $G_1$ checkpoint; if damage cannot be repaired, it triggers apoptosis.

Apoptosis

Programmed cell death that occurs if DNA damage cannot be repaired.

$G_2$ Checkpoint

The mitosis checkpoint where the cell pauses to verify that DNA has replicated properly and to check for DNA damage before entering mitosis.

$M$ Checkpoint

The spindle assembly checkpoint that pauses mitosis to verify that chromosomes are properly aligned and attached to the spindle fibers.

Signal Transduction

The process by which external signaling molecules (such as hormones and growth factors) bind target cell receptors, generating an intracellular molecular signal that turns genes involved in cell cycling on or off.

Chromatin

The combination of DNA and protein molecules that constitutes eukaryotic chromosomes.

Sister Chromatids

Two identical parts of a duplicated chromosome produced by DNA replication and held together at the centromere.

Centromere

The specialized region of a duplicated chromosome that holds sister chromatids together.

Centrosome

The microtubule organizing center of the cell that duplicates and migrates to opposite poles during cell division.

Aster

An array of microtubules extending in a starlike pattern at one of the poles of the spindle apparatus.

Centrioles

Short cylinders of microtubules situated within the centrosome that assist in the formation of spindle fibers in animal cells.

Prophase (Mitosis)

The first phase of mitosis during which chromatin condenses into visible chromosomes, the nuclear envelope fragments, the nucleolus disappears, and spindle fibers appear.

Metaphase (Mitosis)

The mitotic phase in which chromosomes line up along the cell equator (metaphase plate) and the mitotic spindle becomes fully formed.

Anaphase (Mitosis)

The phase of mitosis where sister chromatids separate at the equator and move toward opposite spindle poles as daughter chromosomes.

Telophase (Mitosis)

The final stage of mitosis where chromosomes arrive at opposite poles, decondense back into indistinct chromatin, nucleoli and nuclear envelopes reappear, and the spindle disintegrates.

Cleavage Furrow

An indentation formed by a contractile ring of actin filaments that pinches an animal cell into two distinct daughter cells during cytokinesis.

Meiosis

A two-stage cell division process ($\text{I and II}$) occurring in sex cells to produce four genetically different haploid ($n$) gametes.

Synapsis

The pairing of homologous chromosomes along their lengths during prophase I of meiosis.

Crossing-Over

The exchange of genetic information between homologous non-sister chromatids during synapsis in prophase I, increasing genetic variability.

Independent Alignment

The random orientation of maternal and paternal homologous chromosome pairs at the cell equator during metaphase I, resulting in varied combinations of chromosomes in gametes.

Interkinesis

A resting period between meiosis I and meiosis II during which no DNA replication occurs and chromosomes still consist of two sister chromatids.

Spermatogenesis

The continuous process of sperm production in the testes of males occurring after puberty, generating about $400\text{ million}$ sperm per day.

Oogenesis

The process of egg production in the ovaries of females, which forms one functional ovum and three polar bodies per meiotic cycle.

Polar Bodies

Nonfunctional cellular structures formed during oogenesis that serve to hold discarded sets of chromosomes before disintegrating.

Nondisjunction

The failure of homologous chromosomes to separate during meiosis I, or sister chromatids to separate during meiosis II, leading to abnormal chromosome numbers in daughter cells.

Monosomy

A chromosomal condition in which a cell has only one copy of a particular chromosome; all autosomal monosomies are fatal in humans.

Trisomy

A chromosomal abnormality in which a cell possesses three copies of a particular chromosome; all except trisomy 21 are fatal.

Turner Syndrome

A viable human monosomy characterized by a single $X$ chromosome ($45, X$); affected females typically have short stature, broad shoulders with neck folds, underdeveloped sex organs, and lack menstruation.

Klinefelter Syndrome

A sex chromosome condition in males possessing two or more $X$ chromosomes alongside a $Y$ chromosome ($XXY$), characterized by underdeveloped sex organs, breast development, large hands, and long limbs.

Poly-$X$ Female

A female with extra $X$ chromosomes; individuals with $XXX$ tend to be tall and thin without intellectual disability, whereas individuals with $XXXX$ are severely intellectually disabled.

Jacobs Syndrome

A sex chromosome condition in males possessing an extra $Y$ chromosome ($XYY$), often resulting in tall stature, persistent acne, and speech and reading problems.

Chromosomal Deletion

A structural mutation involving the loss of a piece of a chromosome, such as that seen in Williams syndrome.

Chromosomal Translocation

A structural mutation characterized by the exchange or movement of chromosome segments between nonhomologous chromosomes, as seen in Alagille syndrome.

Chromosomal Duplication

A structural mutation resulting in the presence of a chromosome segment more than once within the same chromosome.

Chromosomal Inversion

A structural alteration where a segment of a chromosome is turned around $180^\circ$, reversing the gene sequence.

Barr Body

A condensed, inactivated $X$ chromosome found in the somatic cell nuclei of mammalian females, ensuring that normal females have only one active $X$ chromosome per cell.