Mitosis and Meiosis Flashcards
- Explain what is meant by diploid and haploid.
Diploid have two sets of chromosomes
Haploid have 1 set of chromosomes
- What does homologous mean?
Chromosomes in a homologous pair are identical in size and shape, genes for same characteristic at the same loci but are not genetically identical.
(e.g Maternal and paternal)
- What are the stages of mitosis
IPMAT:
Interphase, prophase, metaphase, anaphase, and
and telophase.
3a. Describe what happens in interphase
Interphase:
- Growth Phase G1: Proteins produced for the synthesis of more cells, organelles, nucleotides and histone proteins. The cell doubles in size
-S phase: DNA replication takes place, and centrioles replicate
-Growth Phase G2: Organelles grow and divide (replicate), proteins are synthesised (histones and enzymes), ATP increases, and spindle fibres are made from synthesised tubulins (protein).
3a. Describe what happens in Prophase
Early:
- DNA coils and condenses from chromatin into visible chromosomes
- Each chromosome exists as two genetically identical sister chromatids, joined by a centromere.
- Nuclear envelope and nucleolus are still present
Late:
- Nuclear envelope and nucleolus disintegrate.
- Each pair of centrioles move to opposite poles and a network of microtubules form around them and spindle fibres extend between each microtubule at each pole to attach to the centromere.
3a. Describe what happens in Metaphase
Animals:
- Chromosomes align at equator of the cell.
- Sister chromatids are still attached by a centromere.
Plants:
- Do not have centrioles, therefore spindle fibres form without focusing on centrioles.
- Spindle fibres will be straight and parallel to each other.
3a. Describe what happens in Anaphase
- Rapid stage
- Spindle fibres contract and shorten, causing the centromeres to divide and separate sister chromatids
- Spindle fibres pull the chromatids to opposite poles of the cell, centromere first.
3a. Describe what happens in Telophase
- Chromatids have reached the poles and become distinct
- Nuclear envelope and nucleolus reform
- Chromosomes decondense back into chromatin
- Spindle fibres disintegrate
- Why is interphase not counted as part of mitosis?
No cell nuclear division occurs at this point
This stage prepares the cell for mitosis
- What is cytokinesis?
- The physical process of cell division, which divides the cytoplasm of the parental cell into two separate daughter cells.
Animals:
- The cleavage furrow forms microfilaments that attach to the inside of the cell membrane and contract to pull the membrane in.
- Cytokinesis in animals occurs outside to in.
Plants:
- Plants do not cleave.
- Segments of the cell wall align at the equator to form a cell end plate and fuse to form a new cell wall. Process happens from the centre out
- This separates the parental cell into two genetically identical daughter cells
.
- Explain why the DNA content of a cell doubles in interphase and halves in cytokinesis.
DNA doubles in interphase and halves in cytokinesis so that both daughter cells are genetically identical to the parental cell as they have the same DNA content.
- Describe the products of cytokinesis after a mitotic division.
Two genetically identical daughter cells
- What is the significance of mitosis?
- For the growth
- Replaces damaged cells and repairs tissues.
- Regeneration
- Asexual reproduction
- Genetic stability within populations of cells derives from same parental cell (carrying the same hereditary information)
- What is the cause of cancer?
Genetic mutation which causes uncontrolled cell division (mitosis)
Mitosis PRAC: Describe the method for root tip squashes showing the stages of mitosis
1) Cut 10mm from the tip of a growing root and add 20 drops of propionic-orcein stain and 2 drops of 1M HCl.
2) Place the root tip so that the tip is in the stain and cut the end outside the watch glass
3) Remove 2-3mm from the tip of the root and place on a microscope slide.
4) Add 2 drops of stain and warm slide under gentle heat for 5s, then completely break up tissue with/ a mounted needle.
5) Apply coverslip and place slide and coverslip on a paper towel, fold over and squash vertically down on a flat surface with your thumb.
6) Use 10x to identify the zone of cell division (cells are ‘square2 and with large nuclei relative to the cell.
7) Use a 40x lens to observe cells and establish the mitotic index.
- What is the stain used in a root tip squash?
Propionic-acetic stain
- Why is a stain necessary?
Makes the chromosomes more visible
- Why is the root tip used to observe mitosis and not the shoot tip?
It is easier to prep slides of root tips than shoot tips.
Shoot tips are more delicate and surrounded by other material which needs to be removed.
- What is the purpose of the acid?
Hydrochloric acid separates the cells by breaking down the tissue that binds cells together
- Why is the slide ‘squashed’?
So that cells are not overlapping
- What is the formula to calculate mitotic index?
Number of actively diving cells in the field view/total number of cells in field view = Mitotic index
- What does the mitotic index value indicate?
The level of mitotic activity in the cell..
Higher value => More mitosis
Lower value => Less mitosis
- How would you calculate the length of time taken to undergo each stage of mitosis using the root tip squash method?
Record the number of cells in each phase
Time (in minutes) = (no. cells in stage / total no. cells) x total cell cycle time
only works if you know the total time for the full cell cycle
- What is meiosis for?
Two-stage cell division in sexually reproducing organisms that produce four genetically different daughter cells, each with half the number of chromosomes of the parental cell.
