D2.1 Cell and nuclear division Flashcards
Two types of nuclear division covered in this unit?
mitosis and meiosis
cells are?
the basic structural unit of all living organisms
parent cell = ?
mother cell
a parent cell divides to produce __?
2 daughter cells
how do prokaryotic cells divide?
binary fission
how do eukaryotic cells divide?
mitosis
Most eukaryotic organisms are also (in addition to mitosis) capable of carrying out ____?
meiosis
what does meiosis create?
gametes (sex cells)
*meiosis leads to sexual reproduction
what is cytokinesis?
the process of splitting the cytoplasm of the parent cell between the daughter cells
detail the steps of cytokinesis
(in animal cells)
- A network of actin and myosin proteins form a contractile ring that pinches the cell membrane together
- This forms a cleavage furrow, which gradually deepens and eventually splits the cytoplasm to form the two separate daughter cells
- The fluid nature of the double membrane facilitates this process
actin and myosin are also used in?
muscle contraction
detail the steps of cytokinesis
(in plant cells)
- It involves the assembly of a cell plate, formed from the fusion of vesicles containing cell wall materials
- The cell plate grows outwards until it reaches the existing cell wall, which it fuses with, splitting the parent cell into the two daughter cells
figure showing the differences between cytokinesis in plant and animal cells
describe the division of cytoplasm in cytokinesis?
the division of cytoplasm is usually, but not in all cases, equal
what do both daughter cells receive in cytokinesis?
they receive organelles that can only be made by dividing a pre-existing structure, such as:
- at least one mitochondrion (for aerobic cellular respiration to produce ATP)
- peroxisomes
Equal cytoplasmic division results in?
both daughter cells being the same size
(this is important to ensure they have the same structure and function)
what process involves an unequal distribution of cytoplasmic contents?
Oogenesis
what is oogenesis?
the process of producing mature egg cells (or ova) in humans
- it unequally distributes cytoplasmic contents through a series of cell divisions
During oogenesis, how many cell divisions does the primary oocyte undergo?
the primary oocyte undergoes two rounds of cell division
- it results in the production of a secondary oocyte and the first polar body
describe the secondary oocyte produced during oogenesis
It is larger than the first polar body and receives most of the cytoplasmic contents, including organelles, ribosomes, and energy stores
What happens to the secondary oocyte if fertilisation occurs?
it undergoes a second round of cell division, producing a mature ovum (egg cell) and a second polar body
- mature ovum contains the majority of the cytoplasmic contents and organelles required for early embryonic development
- first polar body usually does not divide unless there is sufficient cytoplasm (instead, it will disintegrate and be re-absorbed by the body)
what is the unequal distribution of cytoplasmic contents (in oogenesis) essential for?
it’s important for the development of a healthy and functional embryo
- The smaller size of the polar bodies helps to ensure that the developing embryo has sufficient nutrients and energy to support its growth and development until it can establish its own source of nutrients. It is also necessary to ensure the proper chromosome count (haploid)
what is the mature ovum produced during oogenesis essential for?
Because it has a larger size and greater cytoplasmic content, it can provide the necessary nutrients and cellular machinery required for fertilisation and early embryonic development
