Introduction to Genetics, the Cell Cycle, and Meiosis

Comprehensive practice flashcards covering nucleic acid structure, DNA replication, the eukaryotic cell cycle, mitosis, meiosis, and gametogenesis.

Deoxyribonucleic Acid (DNA)

The double-stranded nucleic acid molecule that stores and encodes hereditary instructions for carrying out cellular activities and protein synthesis.

Nucleotide

The repeating structural subunit (polymer building block) of nucleic acids, consisting of a phosphate group, a deoxyribose sugar, and one of four nitrogenous bases.

Genome

The complete DNA sequence contained within every cell of an organism.

Complementary Base Pairing Rules

The specific pairing rule in DNA where adenine (A) pairs only with thymine (T) via $2$ hydrogen bonds, and cytosine (C) pairs only with guanine (G) via $3$ hydrogen bonds.

Watson and Crick Model

The $1953$ structural model describing DNA as two long chains of nucleotides wound into a twisted ladder shape known as a double helix.

Rosalind Franklin

The scientist who used X-ray diffraction to discover the general shape of DNA, including the position of phosphates, whose experimental data was used by Watson and Crick.

Photo 51

The famous X-ray diffraction photograph of DNA taken by Rosalind Franklin that revealed the helical nature and key dimensions of the molecule.

Sugar-Phosphate Backbone

The structural outer rails of the DNA double helix made of repeating units of deoxyribose sugar and phosphate groups.

Ribonucleic Acid (RNA)

A single-stranded nucleic acid containing ribose sugar and uracil in place of thymine, utilized by the cell to read DNA instructions and synthesize proteins.

Uracil

The nitrogenous base found in RNA that pairs with adenine, substituting for thymine found in DNA.

Pikachurin

A specialized protein encoded by DNA that is involved in transmitting electrical signals in the brain.

Hemoglobin

An iron-containing transport protein coded by DNA that functions to carry oxygen in red blood cells.

Somatic Cells

Typical diploid body cells of an organism that contain two sets of chromosomes ($46$ total chromosomes, or $23$ pairs, in humans).

Gametes

Specialized haploid sex cells (sperm and egg cells) that contain half the chromosome number ($n = 23$ in humans) of somatic cells.

Chromatin

The uncondensed, thread-like form of DNA and associated proteins found in the eukaryotic nucleus during interphase.

Histones

Protein complexes around which eukaryotic DNA winds to efficiently pack and condense genetic material.

Nucleosome

A structural bead-like unit of eukaryotic chromatin formed by DNA coiled around a core of histone proteins.

Sister Chromatids

Two identical copies of a single replicated chromosome that remain joined together at the centromere until nuclear division.

Centromere

The constricted waist region of a duplicated chromosome where two sister chromatids are held together and spindle fibers attach.

Karyotype

A photographic or visual laboratory display showing an individual's complete set of chromosomes arranged and numbered in pairs.

Trisomy 21 (Down Syndrome)

A genetic condition identifiable on a karyotype characterized by the presence of three copies of chromosome $21$ instead of a standard pair.

Interphase

The longest portion of the cell cycle (occupying roughly $90\%$ of the cycle) during which the cell grows, conducts regular metabolic activity, and copies its DNA.

$G_1$ Phase

The first gap subphase of interphase in which the cell performs growth and duplicates cellular contents excluding the chromosomes.

$S$ Phase

The synthesis subphase of interphase during which the cell's $46$ chromosomes are completely replicated.

$G_2$ Phase

The second gap subphase of interphase where the cell double-checks the duplicated chromosomes for errors and performs repairs prior to mitosis.

$G_0$ Phase

A quiescent state of cell cycle arrest in which cells exit the active cell division cycle.

Mitotic (M) Phase

The stage of the cell cycle that encompasses both mitosis (nuclear division) and cytokinesis (cytoplasmic division).

Prophase (Mitosis)

The initial mitotic stage where the nuclear membrane begins to disappear, chromatin condenses into distinct chromosomes, and centrioles migrate to opposite poles to form spindle fibers.

Metaphase (Mitosis)

The stage of mitosis where chromosomes line up individually along the center or equator of the cell (metaphase plate).

Anaphase (Mitosis)

The stage of mitosis during which spindle fibers separate sister chromatids at the centromere, pulling them toward opposite poles as individual chromosomes.

Telophase (Mitosis)

The mitotic stage where chromosomes uncoil back into diffuse chromatin and nuclear membranes reform around the newly separated chromosome sets.

Cleavage Furrow

The indentation of the plasma membrane that pinches the cell inward along the equator during cytokinesis in animal cells.

Cytokinesis

The physical division of the cytoplasm that follows mitosis to produce two distinct, genetically identical daughter cells.

Benign Tumor

An abnormal lump or growth of non-communicating cells that remains localized at its original site without invading neighboring tissues.

Malignant Tumor

A cancerous mass of cells that invades surrounding tissue, enters lymphatic or blood vessels, and can spread through metastasis.

Metastasis

The dissemination of cancer cells from a primary tumor site to distant parts of the body to form secondary tumors.

Mutagen

Any physical or chemical agent, such as ultraviolet light, X-rays, or tobacco smoke, that causes alterations and errors in DNA sequences.

Asexual Reproduction

A form of reproduction involving a single parent that results in offspring with genetic information identical to the parent.

Sexual Reproduction

A mode of reproduction requiring two parents that generates genetically distinct offspring and increases genetic diversity.

Gonads

The primary reproductive organs—specifically the testes in males and ovaries in females—where gamete formation takes place.

Fertilization

The biological process in which haploid gametes from two parents fuse together to produce a single diploid zygote.

Zygote

The single diploid ($2n$) cell produced by the successful fusion of sperm and egg nuclei during fertilization.

Homologous Chromosomes

Pairs of matching chromosomes (one paternal, one maternal) in a diploid cell that possess similar size, shape, and gene arrangements.

Diploid ($2n$)

The chromosomal condition of possessing two full sets of chromosomes, which equates to $2n = 46$ in human somatic cells.

Haploid ($n$)

The chromosomal condition of possessing half the somatic chromosome number, consisting of a single set of $n = 23$ chromosomes in human gametes.

Synapsis

The pairing and physical alignment of homologous chromosomes that takes place during Prophase I of meiosis.

Crossing Over

The reciprocal exchange of genetic segments between non-sister chromatids of homologous chromosomes during Prophase I, producing recombinant chromatids and genetic diversity.

Independent Assortment

The random, independent orientation and alignment of homologous chromosome pairs along the equator during Metaphase I, which yields different chromosome combinations in gametes.

Spermatogenesis

The process of sperm cell production in the testes, starting at puberty from diploid spermatogonia and yielding four viable haploid sperm cells via meiosis.

Oogenesis

The process of egg production in the ovaries, involving unequal cytokinesis that produces a single viable, nutrient-rich ovum and smaller, non-viable polar bodies.