Cell Division Flashcards
(61 cards)
1
Q
What happens in G1 phase of interphase?
A
Growth phase:
- Protein synthesis
- Cell increases in size
- Organelles replicate
2
Q
What happens in S phase in interphase?
A
Synthesis phase:
- DNA is replicated in the nucleus
3
Q
What happens in G2 phase of interphase?
A
Second growth phase:
- Cell continues to increase in size
- Duplicated DNA is checked for errors
4
Q
What happens in G0 phase?
A
The cell leaves the cycle either temporarily or permanently
5
Q
What happens in the mitotic phase?
A
- Mitosis (nucleus divides)
- Cytokinesis (cytoplasm divides)
6
Q
Why might a cell leave the cycle?
A
- Differentiation: A cell that becomes specialised is no longer able to divide
- The DNA of a cell may be damaged
- As you age, the number of these cells in your body increases: linked to age related diseases such as cancer and arthritis
A few types of cells that enter G0 can be stimulated to go back into the cycle, e.g. lymphocytes in an immune response
7
Q
What happens at the G1 checkpoint?
A
End of G1 phase:
- Cell size
- Nutrients
- Growth factors
- DNA damage
8
Q
What happens at the G2 checkpoint?
A
End of G2 phase:
- Cell size
- DNA replication
- DNA damage
9
Q
What happens at the spindle assembly checkpoint?
A
Point in mitosis:
- Chromosomes attached to spindle
10
Q
What is mitosis necessary for?
A
- Growth
- Replacement
- Repair of tissues in multicellular organisms
- Asexual reproduction
11
Q
What happens in prophase?
A
- Chromatin fibres coil & condense = chromosomes
- Nucleolus disappears
- Nuclear envelope disappears
- Spindle formation begins
12
Q
What happens in metaphase?
A
Chromosomes line up on the equator
13
Q
What happens in anaphase?
A
- Centromeres divide
- Chromatids are separated and pulled to opposite poles
14
Q
What happens in telophase?
A
- Chromatids have reached poles = chromosomes
- The 2 new sets of chromosomes assemble at each pole
- Nuclear envelope reforms
- Chromosomes uncoil
- Nucleolus is formed
- Cytokinesis begins
15
Q
Describe cytokinesis in animals
A
- A cleavage furrow forms around the middle of the cell
- The cell-surface membrane is pulled inwards by the cytoskeleton until close enough to fuse around middle, forming 2 cells
16
Q
Describe cytokinesis in plants
A
- Vesicles from Golgi assemble on equator
- Vesicles fuse with each other and membrane, dividing cell into 2
- New cell wall forms along the new sections of membrane
17
Q
What are alleles?
A
Different versions of the same gene
18
Q
What happens in P1 in meiosis?
A
- Chromosomes condense
- Nucleolus disappears
- Nuclear envelope disappears
- Spindle formation begins
- Homologous chromosomes pair up, forming bivalents
19
Q
What can occur in P1 that causes genetic variation?
A
- Crossing over, when bivalents get chromatids entangled and genetic material is transferred between them
20
Q
What is chiasmata?
A
The points at which crossing over occurs (chromatids break and rejoin?)
21
Q
What happens in M1 in meiosis?
A
- Homologous pairs of chromosomes line up on the equator
22
Q
What happens in A1 of meiosis?
A
- Homologous chromosomes are pulled to opposite poles and chromatids stay joined together
- Any potential chiasmata on recombinant chromatids are also pulled apart
23
Q
What can occur in M1 that causes genetic variation?
A
- Independent assortment, when the orientation of each homologous pair is random. It can result in many different combinations of alleles facing the poles
24
Q
What happens in T1 of meiosis?
A
- Chromosomes assemble at each pole
- Nuclear membrane reforms
- Chromosomes uncoil
- Undergoes cytokinesis
25
What happens in P2 of meiosis?
- Chromosomes condenses and become visible
- Nuclear envelope breaks down
- Spindle formation begins
26
What happens in M2 of meiosis?
- Individual chromosomes assemble on equator (like mitosis)
| - Independent assortment occurs
27
What happens in A2 of meiosis?
- Chromatids of individual chromosomes are pulled to opposite poles after division of centromeres (like mitosis)
28
What happens in T2 of meiosis?
- Chromatids assemble at poles (like mitosis)
- Chromosomes uncoil = chromatin
- Nuclear envelope reforms
- Nucleolus becomes visible
- Cytokinesis = 4 haploid daughter cells, genetically different from each other
29
Give 3 specialised animal cells
- Erythrocytes
- Neutrophils
- Sperm cells
30
How are erythrocytes specialised to carry out their function?
- Flattened biconcave shape - increases SA:V ratio
- No nuclei & not many other organelles - increases space available for haemoglobin
- Flexible - squeeze through narrow capillaries
31
How are neutrophils specialised to carry out their function?
- Multi-lobed nucleus - squeeze through small gaps to get to site of infections
- Granular cytoplasm contains many lysosomes
32
How are sperm cells specialised to carry out their function?
- Flagellum - movement
- Mitochondria - supply energy needed to swim
- Acrosome on head - contains digestive enzymes that digest protective layers around ovum
33
Give 3 examples of specialised plant cells
1- Palisade cells
2- Root hair cells
3- Guard cells
34
How are palisade cells specialised to carry out their function?
- Chloroplasts - absorb large amounts of light for PHS
- Chloroplasts can move within cytoplasm - absorb more light
- Rectangular shape - closely pack together to form a continuous layer
- Thin cell walls - increases rate of diffusion of CO2
- Large vacuole - maintain turgor pressure
35
How are root hair cells specialised to carry out their function?
- Long extensions (root hairs) - increase SA to maximise uptake of water and minerals from soil
36
How are guard cells specialised to carry out their function?
- Can open and close depending on whether they lose or gain water
- Cell wall thicker on one side - cell doesn't change shape symmetrically as its volume changes
37
Give 4 examples of specialised animal tissues
- Squamous epithelium
- Ciliated epithelium
- Cartilage
- Muscle
38
How is squamous epithelium specialised to carry out its function?
- Thin - 1 cell thick to allow rapid diffusion
39
How is ciliated epithelium specialised to carry out its function?
- Cilia - move together to move substances
| - Goblet cells - release mucus to trap any unwanted particles present in the air
40
How is cartilage specialised to carry out its function?
- Contains elastin and collagen
| - Prevents ends of bones rubbing together
41
What is muscle?
A tissue that needs to be able to contract in order to move bones
42
Give 3 examples of specialised plant tissue
- Epidermis
- Xylem tissue
- Phloem tissue
43
How is the epidermis specialised to carry out its function?
- Covered by a waxy, waterproof cuticle - reduce water loss
| - Stomata present- allow CO2, water vapour and O2 in/out
44
How is xylem tissue specialised to carry out its function?
- Lignin - structural support
45
How is phloem tissue specialised to carry out its function?
- Sieve tube cells -perforated end so cytoplasm connects from one cell to the next
46
What is an organ?
A collection of tissues that are adapted to perform a particular function in an organism
47
What is an organ system?
Composed of a number of organs working together to carry out a major function in the body
48
What is differentiation?
The process of a cell becoming specialised
49
What are stem cells?
Undifferentiated cells that have the potential to becomes a type of specialised cell
50
What is potency?
A stem cell's ability to differentiate into different cell types
51
What is totipotent?
- Can differentiate into any type of cell (embryo)
52
What is pluripotent?
- Can form all tissue types but not whole organisms
| - They are present in early embryos
53
What is multipotent?
- Can only form a range of cells within a certain type of tissue (adult)
54
Where are blood cells derived from?
Stem cells in the bone marrow
55
What are the 2 types of stem cells?
- Embryonic
| - Tissue/adult
56
What are embryonic stem cells?
- Present at a very early stage of embryo development
- Totipotent
- After 7 days, a mass of cells form (blastocyst) and then they are in a pluripotent state
57
What are adult stem cells?
- Present throughout life from birth
- Found in places like bone marrow
- Multipotent
58
Where are stem cells found in plants?
Meristematic tissue (meristems)
59
Where is meristematic tissue found?
Wherever growth is occuring in plants
60
Give 3 examples of potential stem cell uses
1- Heart disease
2- Type 1 diabetes
3- Spinal injuries
61
Give 3 ethics points on using stem cells
- Destruction of embryos
- Religious objections
- Moral objections
