Cell Cycle and Cell Division

Practice flashcards covering the vocabulary and definitions of the cell cycle, mitosis, and meiosis based on the provided lecture notes.

Cell cycle

The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of the cell, and eventually divides into two daughter cells.

Mitosis

Also known as equational division, a type of cell division that occurs in somatic cells to form body cells.

Meiosis

Also known as reduction division, a type of cell division that occurs in sex cells or gamete-producing cells to form gametes.

Interphase

Referred to as the resting phase, it is the period during which the cell prepares for division by undergoing cell growth and DNA replication in an orderly manner, lasting more than $95\%$ of the cell cycle duration.

Karyokinesis

The nuclear division of the cell cycle involving the separation of daughter chromosomes.

Cytokinesis

The division of the cytoplasm that usually marks the end of the M Phase.

G1 phase (Gap 1)

The interval between mitosis and the initiation of DNA replication where the cell is metabolically active and continuously grows but does not replicate its DNA.

S phase (Synthesis)

The period during which DNA synthesis or replication takes place, doubling the amount of DNA per cell (from $2C$ to $4C$) while the chromosome number remains the same ($2n$).

G2 phase (Gap 2)

The phase where proteins are synthesized in preparation for mitosis while cell growth continues.

G0 phase (Quiescent stage)

An inactive stage of the cell cycle where cells that do not divide further exit the G1 phase but remain metabolically active.

Homologous chromosomes

Chromosomes that have the same length, centromere location, and the same gene sequences and positions.

Diploid ($2n$)

Cells that contain two copies of each chromosome, such as human somatic cells.

Haploid ($n$)

Cells with only one copy of each chromosome, such as human sex cells (eggs and sperm).

Prophase

The first stage of mitosis marked by the initiation of condensation of chromosomal material and the move of duplicated centrioles to opposite poles.

Kinetochores

Small disc-shaped structures at the surface of the centromeres that serve as sites of attachment for spindle fibers.

Metaphase plate

The plane of alignment of the chromosomes at the equator during metaphase.

Anaphase

The stage of mitosis characterized by the simultaneous splitting of centromeres and the migration of chromatids toward opposite poles.

Telophase

The final stage of mitosis where chromosomes decondense, lose their individuality, and the nuclear envelope, nucleolus, golgi complex, and ER reform.

Cleavage furrow

The appearance in the plasma membrane of animal cells that gradually deepens to divide the cytoplasm into two cells.

Cell-plate

The simple precursor in plant cells that represents the middle lamella between the walls of two adjacent cells during cytokinesis.

Syncytium

A multinucleate condition that arises when karyokinesis is not followed by cytokinesis, such as in liquid endosperm in coconut.

Synapsis

The process of association or pairing together of homologous chromosomes during the zygotene stage of Prophase I.

Synaptonemal complex

A complex structure formed during chromosome synapsis in the zygotene stage.

Bivalent or Tetrad

The complex formed by a pair of synapsed homologous chromosomes.

Crossing over

The exchange of genetic material between two homologous chromosomes occurring at recombination nodules during the pachytene stage.

Recombinase

The enzyme involved in the enzyme-mediated process of crossing over.

Chiasmata

X-shaped structures visible in the diplotene stage representing the sites of crossovers between recombined homologous chromosomes.

Interkinesis

The generally short-lived stage between the two meiotic divisions.