Structure of Chromosome, Cell Cycle and Division

Vocabulary-style practice flashcards covering chromosome structure, DNA composition, the cell cycle phases (Interphase, Mitosis, Cytokinesis), and Meiosis.

Chromosomes

Discrete units composed of DNA and protein organized within the nucleus, which condense from chromatin fibers.

Chromatin

A complex consisting of approximately $40\%$ DNA ($\text{deoxyribonucleic acid}$) and $60\%$ Histone proteins.

Walther Flemming

The German scientist who discovered cell division in the larvae of salamanders in $1882$, naming the process mitosis.

Double-helical structure

The shape of the DNA molecule worked out by Watson and Crick in $1953$ following initial studies by Rosalind Franklin.

Nucleotide

The basic unit of DNA composed of three components: a phosphate, a pentose sugar, and a nitrogenous base.

Complementary Nitrogenous Bases

Pairs formed by hydrogen bonds: Adenine ($A$) pairs with Thymine ($T$) via a double bond, and Guanine ($G$) pairs with Cytosine ($C$) via a triple bond.

Nucleosome

A structural unit of DNA packaging consisting of a DNA strand wound around a core of histone proteins known as an octamer.

Centromere

The specific point of attachment where two sister chromatids are joined and where spindle fibers attach during division.

Autosomes

Non-sex chromosomes that determine the general characteristics of the body.

Heterosomes

Also known as allosomes, these are the sex chromosomes that determine the sex of the offspring.

Genes

Specific sequences of nucleotides on a chromosome that encode particular proteins and serve as hereditary units.

Cell Cycle

An organized and predictable series of events where a cell grows, synthesizes materials, and duplicates its DNA before splitting.

Interphase

The non-dividing 'resting phase' of the cell cycle consisting of the First Growth Phase ($G_1$), Synthesis Phase ($S$), and Second Growth Phase ($G_2$).

Karyokinesis

The part of M-phase characterized by the division of the cell nucleus through four phases: Prophase, Metaphase, Anaphase, and Telophase.

Cytokinesis

The division of the cell's cytoplasm that occurs after karyokinesis to produce two daughter cells.

Prophase

The first phase of mitosis where centrioles move apart, chromosomes become distinct as paired chromatids, and the nuclear membrane disappears.

Metaphase

The phase where chromosomes line up in one plane at the equatorial plane and attach to the spindle by their centromeres.

Anaphase

The phase where centromeres split and sister chromatids are pulled towards opposite poles by contracting spindle fibers.

Telophase

The final phase of mitosis where daughter chromosomes reach the poles, chromatin thins out, and nucleoli reappear.

Mitosis

A type of cell division resulting in two identical daughter cells with the same diploid ($2n$) number of chromosomes.

Meiosis

A reduction division that produces haploid ($n$) sex cells or gametes, halving the chromosome number.

Haploid ($n$)

A cell that contains a single set of unpaired chromosomes.

Diploid ($2n$)

A cell that contains two sets of homologous chromosomes.

Chaisma

The point of attachment between two non-sister chromatids of a pair of homologous chromosomes during crossing over.

Crossing Over

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

Genetic Recombination

The mixing of genes during meiotic division that provides variations in offspring.