Cell Cycle, Mitosis, Meiosis, and Genetics

Comprehensive vocabulary flashcards covering the cell cycle, mitosis, meiosis, cancer biology, and Mendelian genetics.

Gamete

A haploid ($n$) sex cell (such as a sperm or egg) that contains half of a parent's DNA chromosomes and combines with another during fertilization to form an offspring.

Zygote

The diploid ($2n$) cell produced when fertilization merges gametes from two parents, forming the first cell of a new organism with a full set of chromosomes.

Haploid

Containing only one full set of genetic information or chromosomes ($n$), representing half the chromosome number of a somatic cell.

Diploid

Containing two sets of genetic information or chromosomes ($2n$), with one full set inherited from each parent.

Meiosis

A process of cell division in sexually reproducing organisms where a diploid nucleus undergoes two divisions to produce four genetically distinct haploid nuclei.

Crossing Over

The exchange of genetic material between homologous chromosomes during prophase I of meiosis, creating new combinations of alleles.

Independent Assortment of Chromosomes

The process occurring in metaphase I and anaphase I where maternal and paternal chromosome pairs line up randomly at the cell equator and split apart.

Random Fertilization

A source of genetic diversity in sexual reproduction where any unique sperm cell can fuse with any unique egg cell.

Allele

Alternative forms of a gene arising from different mutations, representing any of the possible forms that a hereditary characteristic can take.

Dominant Allele

An allele that encodes a functional protein exerting its phenotypic effect whenever it is present.

Recessive Allele

An allele that encodes a protein whose phenotypic effect is masked whenever a dominant allele is also present.

Mendel's Law of Segregation

The principle stating that each individual possesses two alleles for each trait, which separate during gamete formation so each gamete carries only one allele for each gene.

Heterozygous

Having two different alleles for a specific gene (such as $Yy$), indicating that each parent contributed different genetic information.

Homozygous

Having two identical alleles for a specific gene, indicating that both parents contributed the same gene versions.

Mendel's Law of Independent Assortment

The principle stating that alleles of two or more different genes sort into gametes independently of one another.

Incomplete Dominance

A form of inheritance in which neither allele is completely dominant over the other, resulting in an intermediate phenotype.

Codominance

A pattern of inheritance in which two different alleles are both fully expressed in the phenotype.

Pleiotropy

A genetic phenomenon where a single gene affects multiple seemingly unrelated phenotypes or systems in the body.

Cell Theory

The three-part biological principle stating that all living organisms are composed of cells, the cell is the basic structural unit, and all cells arise from preexisting cells.

Mitosis

The division of a single cell nucleus into two genetically identical daughter nuclei, used for growth, tissue repair, replacement, and asexual reproduction.

Rapidly Dividing Human Cells

Human cell types that undergo cell division most often, specifically skin cells, red blood cells, and cells of the intestines.

Non-Dividing Human Cells

Specialized human cell types that almost never undergo cell division, specifically cells in the nervous system and cells in the heart muscle.

$G_1$ Phase

The 'first gap' stage of the cell cycle, serving as an initial active cellular growth stage.

$S$ Phase

The synthesis phase of the cell cycle during which genetic material (DNA) is duplicated.

$G_2$ Phase

The 'second gap' stage of the cell cycle, functioning as a secondary cellular growth phase prior to division.

$M$ Phase

The mitotic phase of the cell cycle involving the formation of two cell nuclei from one, followed by cytokinesis.

$G_0$ Phase

A resting state entered by cells that are finished dividing or have temporarily left the cell cycle.

Chromatin

The cellular material that constitutes chromosomes, consisting of two main components: DNA and proteins.

Sister Chromatids

A pair of two identical chromosome 'threads' formed by chromosome duplication during the $S$ phase.

Centromere

The structural region that links a pair of sister chromatids together near their centers.

Prophase (Mitosis)

The first phase of mitosis during which chromosome strands uncoil and condense.

Prometaphase

The transitional mitotic stage occurring between prophase and metaphase.

Metaphase (Mitosis)

The mitotic stage where chromosomes line up along the cell's equator and attach to spindle fibers.

Anaphase (Mitosis)

The mitotic stage where sister chromatids separate and move toward opposite centrosomes.

Telophase

The final stage of mitosis during which nuclear division concludes before or during cytokinesis.

Cytokinesis

The division of the cytoplasm where the plasma membrane pinches completely off in the center to form two separate daughter cells.

Cancer

A disease characterized by excessive cell division and growth, where abnormal cells crowd out normal functioning cells.

Benign Tumor

An abnormal cell mass whose growth remains confined to its original location.

Malignant Tumor

A severe, invasive abnormal growth that impairs normal tissue function and can spread throughout the body.

Metastasize

The process by which tumor cells detach and spread to other parts of the body.

Homologous Chromosomes

Pairs of chromosomes in diploid cells that contain genes for the same proteins; humans possess $23$ pairs.

Metaphase I

The meiotic stage where homologous chromosome pairs line up side-by-side along the center of the cell.

Anaphase I

The meiotic stage where homologous chromosome pairs separate to opposite poles while sister chromatids remain attached at their centromeres.

Anaphase II

The meiotic stage where centromeres split and separated sister chromatids migrate toward opposite poles.

Evolutionary Advantage of Sexual Reproduction

A reproductive strategy favored in changing environments because genetic variation offers a better chance of surviving stressful living conditions.