Eukaryotic and Prokaryotic Cell Division and Meiosis

Comprehensive vocabulary flashcards covering the cell cycle, eukaryotic and prokaryotic cell division, regulation, cancer development, and the stages/strategies of sexual reproduction and meiosis as described in the lecture.

Zygote

An embryo formed from the fusion of a sperm and egg during fertilization that begins life as a single fertilized egg.

Genome

A cell's DNA packaged as a double stranded DNA molecule; in prokaryotes, it is a single loop, while in eukaryotes, it consists of several linear molecules.

Plasmids

Smaller loops of DNA found in some prokaryotes that are not essential for normal growth but can be exchanged between bacteria, often spreading antibiotic resistance.

Ploidy

The number of complete sets of chromosomes in a cell, denoted by the letter $n$.

Diploid ($2n$)

A cell containing two matching sets of chromosomes, one from each parent.

Haploid ($1n$)

A cell containing only one set of chromosomes, typical of gametes.

Homologous chromosomes

Matched pairs of chromosomes that are the same length and have genes in the exact same location, or locus.

Genes

Specific nucleotide segments that serve as the functional units of chromosomes by encoding for certain proteins that determine specific characteristics.

Allele

Alternative forms of a gene that code for the same trait but may lead to different variations, such as blood types $A$, $B$, or $O$.

Chromatin

A level of DNA structure where DNA wraps around histone proteins, resulting in a form that is seven times shorter and five times wider than the raw DNA molecule.

Sister chromatids

Two identical copies of the same chromosome linked by cohesion proteins, formed after DNA replication during the S phase.

Centromere

The area of greatest connection between sister chromatids, typically located near the center of the replicated chromosome.

Interphase

The major phase of the cell cycle where the cell undergoes normal growth and DNA replication in preparation for division, consisting of $G1$, $S$, and $G2$ stages.

G1 Phase (First Gap)

The stage of interphase characterized by the accumulation of nucleotides for DNA replication, amino acids for proteins, and energy reserves.

S Phase (Synthesis of DNA)

The middle part of interphase where DNA replication occurs, resulting in the production of sister chromatids and the duplication of the centrosome.

Mitotic spindle

An apparatus of spindle fibers that orchestrates the movement of chromosomes during cell division.

G2 Phase (Second Gap)

The final stage of interphase where the cell replenishes energy stores, synthesizes proteins for chromosome movement, duplicates some organelles, and dismantles the cytoskeleton.

Karyokinesis

The first major portion of the mitotic phase, referring specifically to nuclear division.

Cytokinesis

The physical separation of the cytoplasmic components into two daughter cells, which may or may not occur after karyokinesis.

Prophase

The first phase of mitosis where the nuclear envelope disintegrates, organelles move to the outer edges, the nucleolus disappears, and chromosomes coil tightly.

Kinetochore

A protein formed in the centromeric region during prometaphase that attracts the mitotic spindle to orient sister chromatids toward opposite poles.

Metaphase plate

The equatorial plane located approximately halfway between the poles where chromosomes align during metaphase.

Anaphase

The stage of mitosis where cohesion proteins dissolve, sister chromatids separate at the centromere, and chromosomes move rapidly toward opposite poles.

Telophase

The stage where chromosomes reach opposing poles, decondense back into chromatin, the spindle breaks apart, and the nuclear envelope redevelops.

Cleavage furrow

A fissure created in animal cells by a contractile ring that pulls the equator of the cell inward until the membrane is cleaved in two.

Cell plate

A new structure formed in plant cells from dissolved Golgi apparatus vesicles that will eventually become the new cell wall dividing the daughter cells.

G0 phase

An inactive or quiescent stage where cells exit the cell cycle and are not actively preparing to divide, often due to unfavorable environmental conditions.

P53 and P21

Negative regulator molecules that can halt the cell cycle in response to stress, making the cell less likely to move into the S phase.

Proto-oncogenes

Normal genes that code for positive cell-cycle regulators; when mutated, they can become oncogenes.

Oncogenes

Mutated versions of proto-oncogenes that have the potential to drive the cell cycle forward even when the cell is not ready, contributing to cancer.

Tumor suppressor genes

Genes that code for negative regulator proteins which act like brakes to halt the cell cycle; a failure in these, such as a damaged $P53$ regulator, can lead to uncontrolled cell growth.

Binary fission

The process of asexual reproduction in prokaryotes that produces two identical daughter cells from a single parent cell.

Meiosis

A type of cell division that produces haploid sex cells (gametes), involving two rounds of division to introduce genetic variation.

Crossing over

A key event in Prophase I of meiosis where maternal and paternal genes are exchanged on chromatids to create unique genetic combinations.

Independent assortment

The random alignment of homologous chromosomes on the metaphase plate during Metaphase I, creating $2^n$ possible genetic combinations (over $8$ million in humans).

Interkinesis

A brief interphase between Meiosis I and Meiosis II in some species, which lacks an S phase and thus involves no DNA duplication.

Germ cells

Specialized diploid cells produced in the gonads (testes and ovaries) that are capable of undergoing both mitosis and meiosis.

Spores

Haploid cells produced by the zygote via meiosis in fungi and some algae, which can remain dormant and later divide mitotically to form a multicellular adult.

Gametophyte

The haploid multicellular stage in the plant life cycle that produces gametes from specialized cells through mitosis.

Sporophyte

The multicellular diploid stage in plants formed by the mitotic division of a zygote, which produces haploid spores through meiosis.