Chapter 7.2: Asexual Reproduction Results in Genetically Identical Daughter Cells

Flashcards from Chapter 7.2 of Principles of Life, 3rd Edition.

Cell division events

Requires:

• Cell division signals (initiated from any source)

• DNA replication (for each cell)

• DNA segregation (to ensure correct copies)

• Cytokinesis (division of cells with membrane)

Binary fission

Type of cell division found in prokaryotes, involving growth, replication, then separation and segregation

• Often triggered by good external conditions

Prokaryotic chromosome sites

Sites associated with chromosome replication before segregation, these include

• Ori (the origin of replication)

• Ter (the terminus of replication)

Prokaryotic DNA segregation

This starts with replication, with the ori regions moving towards opposite ends of the cell as proteins are bound and ATP is hydrolyzed for support

Prokaryotic cytokinesis

This occurs with DNA segregation, as the cell pinches in with a ring of fibers called the Z-ring primarily made of tubulin

Z-ring

A ring of fibers that aids in prokaryotic cytokinesis through the pinching of the membrane

Cell cycle

The phases through which a single eukaryotic cell passes to produce daughter cells as needed, broken into:

• G1 phase (growth and normal functioning awaiting signals)

• S phase (active replication)

• G2 phase (preparation for mitosis)

• M phase (DNA segregation for mitosis and cytokinesis)

Mitosis

The cell division process in eukaryotes, giving rise to two daughter nuclei that each contain the same number of chromosomes as the parent nucleus

• Generally consists of five stages

Chromatin

The heavily compacted combination of DNA and its associated proteins for binding, such as the positively-charged histones

• This condensation varies by region and time, with more condensation during M phase

Centromere

A structure that holds two replicated chromosomes together

Chromosome arm

The portion of the DNA molecule in each side of the centromere

• Unreplicated chromosomes have 2

• Replicated chromosomes have 4

Sister chromatids

The set of two essentially identical replicated DNA molecules, joined together before being separated in mitosis for chromosome distributions

Karyotype

The number and sizes of the condensed chromosomes in a cell’s M phase

Eukaryotic DNA replication

This occurs at numerous origins of replication during a specific part of the cell cycle, not overlapping with segregation or cytokinesis

Eukaryotic DNA segregation

Due to multiple chromosomes, DNA must be highly condensed before this process after which it is moved by a spindle that aids in movement

Prophase

The first stage of mitosis, where:

• Chromosomes condense

• Kinetochores appear on centromere sides, one per chromatid, for movement

• Microtubule-comprised centrosomes and spindles form and self-orient

Centrosomes

Structures that orient themselves at the poles of the cell during prophase

• Made up of a pair of centrioles, comprised of microtubules

• One is duplicated during the S phase for use later on

Spindle

The microtubules that begin attachment to the kinetochores during prophase and prometaphase as they gain stability and the nuclear envelope breaks down

Metaphase

The third stage of mitosis, where chromosomes are aligned at the midline of the cell by kinetochores

Anaphase

The fourth stage of mitosis, where sister chromatids are separated into separate chromosomes as kinetochores are pulled apart

Telophase

The fifth stage of mitosis, where:

• A nuclear envelope forms after separation

• Chromosomes become less compact

• The spindle disappears

Cytokinesis

The division of the cell’s cytoplasm that occurs after mitosis, resulting in completely-formed daughter cells

• In animals, a contractile ring forms under the cell membrane, forming a cleavage furrow

• In plants, vesicles from the Golgi apparatus appear along the plane of cell division, forming a new cell membrane and cell wall from a plate