Gr 11 cell cycle

Back to Cell Cycle

You may see many textbooks or resources use different pictures to show the Cell Cycle, but they all show the same information.

Watch first to learn about Cell Cycle and Mitosis

The cell cycle is an ordered set of events which culminates in the division of a cell into two daughter cells

Interphase

The stage in the development of a cell between two successive divisions

This phase of the cell cycle is a continuum of three distinct stages:

G₁ – First intermediate gap stage in which the cell grows and prepares for DNA replication
S – Synthesis stage in which DNA is replicated
G₂ – Second intermediate gap stage in which the cell finishes growing and prepares for cell division

M phase

The period of the cell cycle in which the cell and contents divide to create two genetically identical daughter cells

This phase is comprised of two distinct stages:

Mitosis – Nuclear division, whereby DNA (as condensed chromosomes) is separated into two identical nuclei
Cytokinesis – Cytoplasmic division, whereby cellular contents are segregated and the cell splits into two

Watch second, afterlearning about Cell Cycle and Mitosis

Interphase

Interphase is an active period in the cell cycle when many metabolic reations occur

Many events need to occur in interphase to prepare the cell for successful division

These key processes include:

Organelle duplication – Organelles must be duplicated for twin daughter cells
Cell growth – Cytoplasmic volume must increase prior to division
Transcription / translation – Key proteins and enzymes must be synthesised
Obtain nutrients – Vital cellular materials must be present before division
Respiration (cellular) – ATP production is needed to drive the division process

Mnemonic:

Chromatin:

DNA is usually loosely packed within the nucleus as unravelled chromatin
In this unravelled form, the DNA is accessible to transcriptional machinery and so genetic information can be translated
DNA is organised as chromatin in all non-dividing cells and throughout the process of interphase

Chromosome:

DNA is temporarily packaged into a tightly wound and condensed chromosome prior to division (via supercoiling)
In this condensed form, the DNA is able to be easily segregated however is inaccessible to transcriptional machinery
DNA is organised as chromosomes during the process of mitosis (condense in prophase, decondense in telophase)

Chromosome versus Chromatid

A chromosome is the condensed form of DNA which is visible during mitosis (via microscopy)

As the DNA is replicated during the S phase of interphase, the chromosome will initially contain two identical DNA strands

These genetically identical strands are called sister chromatids and are held together by a central region called the centromere

When these chromatids separate during mitosis, they become independent chromosomes, each made of a single DNA strand

Control of Cell Cycle

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