1.6 Cell devision Flashcards
Two main phases of the cell cycle
Interphase
M phase
Interphase
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
Mitosis
Cytokinesis
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
Processes that occur in the interphase
DNA replication Organelle duplication Cell growth Transcription / translation Obtain nutrients Respiration (cellular)
Features of chromatin
loosely packed
DNA is accessible to transcriptional machinery and so genetic information can be translated
in all non-dividing cells and throughout the process of interphase
Features of chromosome
packaged into a tightly wound and condensed chromosome
DNA is able to be easily segregated however is inaccessible to transcriptional machinery
during the process of mitosis (condense in prophase, decondense in telophase)
Chromosome vs 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
Mitosis
the process of nuclear division, whereby duplicated DNA molecules are arranged into two separate nuclei
Four stages of mitosis
prophase, metaphase, anaphase, telophase
Before mitosis
Interphase:
DNA is present as uncondensed chromatin
DNA is contained within a nucleus
Centrosomes and other organelles have been duplicated
Cell is enlarged in preparation for division
Prophase
spindle microtubules are growing
chromosomes are becoming shorter and fatter by supercoiling
each chromosome consists fo two identical chromatids formed by DNA replication in interphase and held together by a centromere
spindle microtubules extend from each pole to the equator
Metaphase
the nuclear membrane has broken down and chromosomes have moved to the equator
spindle microtubules from both poles are attached to each centromere, on opposite sides
Anaphase
the centromeres divide to allow sister chromatids to separate
spindle microtubules pull the genetically identical chromosomes to opposite poles
