Grade 11 Scientific Biology: Chromosome Structure, Mitosis, and Ring Chromosome 14 Syndrome

Vocabulary study cards covering eukaryotic chromosome anatomy, mechanisms and pathology of Ring Chromosome 14 Syndrome, mitotic stages, cytogenetic karyotyping techniques, and early reproductive development.

Replicated Chromosome Anatomy

The structural organization of a eukaryotic chromosome following replication, consisting of two sister chromatids joined at a centromere, delineated into a short arm (p arm) and a long arm (q arm), and capped by telomeres.

Ring Chromosome 14 Syndrome [$r(14)$]

A chromosomal condition caused by double terminal breaks near the tips of both the short (p) and long (q) arms of chromosome 14; the loss of telomeres leaves exposed ends that fuse together into a circular ring.

Telomere

A protective DNA cap situated at the terminal ends of a chromosome that prevents degradation and unauthorized end-to-end joining; terminal breaks that shed telomeres result in 'sticky' ends prone to ring formation.

Centromere

The specialized, constricted chromosomal locus that holds two sister chromatids together and serves as the assembly site for spindle fiber attachment during mitosis.

Acrocentric Chromosome

A chromosome whose centromere is situated close to one end, giving it a very short p arm and a long q arm; in human chromosome 14, the p arm contains redundant ribosomal genes duplicated on chromosomes 13, 15, 21, and 22.

Mosaicism

The presence of two or more genetically distinct cell lines within an individual; in ring chromosome 14, mitotic instability causes interlocking rings to stretch, break, or fail to segregate, producing a mix of normal, ring-14, and monosomic cells.

Microcephaly

An abnormally reduced head circumference observed in patients with Ring Chromosome 14 Syndrome, stemming from ring instability that delays mitotic cell division and slows bodily growth.

Strabismus

An ocular condition characterized by crossed eyes, arising in Ring Chromosome 14 Syndrome due to the deletion of specific eye development genes located on the long arm (q arm).

Karyotype Test

A cytogenetic procedure in which cells are cultured, arrested in metaphase, stained, and microscopically analyzed to classify and order chromosomes by size, centromere location, and banding pattern.

Colchicine

A chemical agent added during karyotype preparation that disrupts spindle fiber assembly, thereby arresting dividing white blood cells specifically at metaphase.

FISH Test (Fluorescence In Situ Hybridization)

A molecular cytogenetic diagnostic technique using glowing fluorescent probes to detect whether specific target sequences, such as the long-arm telomere and tip region of chromosome 14, are present or missing.

Microarray Test

A high-resolution diagnostic genomic tool used to quantify the exact base-pair size and extent of missing or deleted DNA segments on chromosome 14.

Mitosis

A fundamental mode of cell division in somatic cells ($2n$) that produces two identical daughter cells essential for growth, regeneration, and tissue repair.

Prophase

The initial mitotic phase characterized by the condensation of chromatin into distinct chromosomes, the disintegration of the nuclear membrane, and the formation of the spindle apparatus and two asters.

Metaphase

The second mitotic stage during which double-chromatid chromosomes align along the center of the spindle fibers to construct an equatorial plate.

Anaphase

The mitotic phase defined by the cleavage of centromeres and the active migration of separated sister chromatids toward opposite poles of the cell via polar ascension.

Telophase

The final stage of mitosis during which two identical sets of single-chromatid chromosomes decondense within newly reforming nuclear envelopes, accompanied by cytoplasmic division.

Polar Ascension

The directed migration of separated sister chromatids toward opposite cell poles during mitotic anaphase.

Equatorial Plate

The plane equidistant between the two spindle poles where duplicated chromosomes align during metaphase.

Interphase (Phase Y)

The nondividing phase of the cell cycle preceding mitosis, encompassing stages such as $G_1$ (single chromatid state) and $G_2$ (double chromatid state), dedicated to cell growth and DNA chromatid duplication.

Fertilization

The union of a haploid male gamete (sperm cell, $23\,\text{chr}$) and a haploid female gamete (oocyte, $23\,\text{chr}$) to form a single diploid cell.

Zygote

The initial diploid cell ($2n = 46\,\text{chrs}$) produced by fertilization that subsequently undergoes cleavage and differentiation into an embryo and fetus.

Oviduct (Fallopian Tube)

The anatomical channel of the female reproductive system that receives the released oocyte from the ovary and serves as the physiological site of fertilization.

Embryonic Cell Cycle Duration

The total duration of one cleavage cycle ($\text{interphase} + \text{mitosis}$); when an early human embryo reaches $16\,\text{cells}$ ($2^n = 16 \Rightarrow n = 4\,\text{mitoses}$) in $72\,\text{hours}$, each cycle lasts $\frac{72}{4} = 18\,\text{hours}$.