The cell cycle Flashcards
what is a stem cell
an undifferentiated cell which can actively go through the cell cycle
define differentiation
the physical change of a cell into a final specialised form
what are specialised cells
cells with a designated shape, chemistry and role
which cells do not go through mitosis
differentiated cells
how are new cells formed from our tissues
all tissues contain a base layer of stem cells which differentiate to replace any cells that have died
how many chromosomes in a single dna molecule
one
how many chromosomes in two sister chromatids attached by a protein complex (two dna molecules)
one
when and how are chromosomes visible
they are visible when supercoiled and can be seen under a light microscope
Name the states of the cell cycle
- interphase (G1)
- interphase (S)
- interphase (G2)
- mitosis
- cytokinesis
Describe what occurs during interphase (G1)
Cell increases in mass, duplicates all cellular contents and organelles excluding chromosomes
What occurs during interphase (S)
Semi-conservative dna replication of all 46 chromosomes
What occurs during interphase (G2)
Cell double checks that both S and G1 have been fully completed. Makes any needed repairs.
What is mitosis
Nuclear division
What is cytokinesis
Division of the cell body
What state are chromosomes in during interphase
Diffuse and uncoiled (to unwind and separate)
What state are chromosomes in during mitosis
Short, compact - supercoiled
(More compact so can separate within the confides of the cell)
What is a chromatin
DNA molecules associated with proteins called histones
Name the stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
Describe what happens during prophase
(Occurs at different rates)
- nuclear envelope disintegrates
- nucleolus disintegrates
- spindle fibres form (forming a spindle)
- chromosomes condense and coil becoming visible
Describe what happens during metaphase
- chromosomes attach to the spindle via their centromeres
- centromeres break
- line on the equatorial plane
Describe what happens during Anaphase
- sister chromatids are pulled to opposite sides of the cell
Describe what happens during telophase
- two new nuclear envelopes form
- Chromatin/dna becomes diffuse
- nucleolus reforms
What is the phase between prophase and metaphase called
Prometaphase
Why does metaphase not slide into anaphase
The chromatids must be separated at the same time, the cell has to check that all chromosomes are attached before separating
