Cell Division Flashcards
What is the cell cycle
a highly ordered sequence of events that takes place in a cell in order to grow and divide
resulting in two genetically identical daughter cells
What is Interphase
the first stage of the cell cycle
not a resting phase as this is when the cell carries out all of its major functions such as producing enzymes whilst also preparing for cell division
What occurs during Interphase
G1 - cell grows and new proteins and organelles are synthesised
G1 Checkpoint - checks all chemicals needed for respiration are present and that there is no damage to DNA before entering the S phase
S - DNA replicated in the nucleus
G2 - cell grows more in preparation for mitosis
G2 Checkpoint - ensures all DNA has been replicated correctly and that there is no damage to DNA so cell can enter mitosis
What is G0 phase
when the cell temporarily or permanently leaves the cycle
What would cause a cell to enter the G0 phase
- cell differentiation
- DNA damage
What is meant by senescent
majority of normal cells can only divide a limited number of times and eventually become senescent
as you get older the amount of these cells in your body increases and is linked with age related diseases such as cancer and arthritis
What does mitosis ensure
both daughter cells are genetically identical
What is mitosis used for
growth, replacement and repair of tissues in multicellular organisms
necessary for asexual reproduction
Why is it important that the chromatids are kept close together during mitosis
so that they can be precisely manoeuvred and segregated equally; one each into the two new daughter cells
What occurs during Prophase
chromosomes condense becoming shorter, fatter and more visible
small proteins called centrioles begin moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle
nuclear envelope breaks down so the chromosomes lie free in the cytoplasm
What occurs during metaphase
chromosomes line up in the middle of the cell forming the metaphase plate, and begin attaching to the spindles by their centromeres
Metaphase checkpoint occurs and ensures that all chromosomes are attached to the spindle before mitosis continues
What occurs during anaphase
centromeres divide separating the sister chromatids
the spindles contract pulling the chromatids to opposite poles of the cell
What occurs during telophase
spindles break down and the chromosomes uncoil
nuclear envelopes form around each new set of chromosomes, forming nucleolus
What is the difference between cytokinesis in an animal cell vs a plant cell
Animal cells;
cleavage furrow forms around the middle of the cell and the cell membrane is pulled inwards by the cytoskeleton until it is close enough to fuse around the middle, forming two cells
Plant cells;
due to cell walls, cleavage furrow cannot form so vesicles from Golgi apparatus begin to assemble in the same place as where the metaphase plate was, vesicles then fuse with each other and the cell surface membrane, dividing the cell into two.
What is Meiosis
Type of cell division that happens in the reproductive organs to produce gametes
It produces 4 genetically different/unidentical haploid cells as each cell ends up with a different combination of chromosomes
