Cell division, cell diversity & cell differentiation 2.6 Flashcards
(53 cards)
1
Q
What are the phases of the cell cycle?
A
- interphase
- mitosis
- cytokinesis
2
Q
What is mitosis?
A
Type of nuclear division that maintains the chromosome number
3
Q
What is the importance of mitosis?
A
- asexual reproduction
- growth
- tissue repair
4
Q
What are the stages of mitosis?
A
- prophase
- metaphase
- anaphase
- telophase
- cytokinesis
5
Q
What happens during prophase in mitosis?
A
- DNA supercoils and condenses becoming visible
- nuclear envelope breaks down
- spindle fibres form
6
Q
What happens during metaphase in mitosis?
A
- Chromatids attach to the spindle fibres by their centromeres
- line up in the equator region
7
Q
What happens during anaphase in mitosis?
A
- centromere of each pair of chromatids splits
- spindle fibres contract
- sister chromatids are pulled to opposite directions
8
Q
What happens during telophase in mitosis?
A
- chromosomes reach the poles
- nuclear envelope forms
- chromosomes uncoil and decondense
9
Q
What happens during cytokinesis in mitosis?
A
Plasma membrane folds inwards and rips the cytoplasm
10
Q
What is cytokinesis?
A
Division of the cytoplasm of a cell following mitosis
11
Q
What are the phases of interphase?
A
- G1
- S
- G2
12
Q
What are the main checkpoints during the cell cycle?
A
- G1 checkpoint
- S checkpoint
- G2 checkpoint
- metaphase checkpoint
13
Q
What happens at the G1 checkpoint?
A
- chromosomes checked for damage
- if damage is found the cell will not progress into S phase until damage is fixed
14
Q
What happens at the S checkpoint?
A
- chromosomes checked to ensure they have been replicated correctly
- cell cycle stops if error found
15
Q
What happens at the G2 checkpoint?
A
- additional check for DNA damage
- if damage found cycle is delayed until repairs are made
16
Q
What happens at the M checkpoint?
A
Check to ensure spindle fibres are attached correctly to the chromosomes before anaphase
17
Q
What are the purpose of the checkpoints?
A
- prevent uncontrolled division
- detect and repair damage to DNA
- ensure DNA is only duplicated once
18
Q
What happens during the M phase of the cell cycle?
A
- cell stops growing
- cell undergoes nuclear division
19
Q
What happens during the G0 phase of the cell cycle?
A
- It is a resting phase
- triggered in early G1 by checkpoint chemical
- cells may stay in this phase for a very long time (neurones)
- cells may undergo apoptosis, differentiation or senescence
20
Q
What happens during the G1 phase of the cell cycle?
A
- cell growth & increases in size
- organelles duplicate
- trancription to create RNA
- protein synthesis
21
Q
What happens during the S phase of the cell cycle?
A
- cell now has to commit to completing the cycle
- DNA replicates
- rapid due to DNA being exposed to random mutations
22
Q
What happens during the G2 phase of the cell cycle?
A
- Cells grows
- proteins involved with mitosis are stimulated
- errors are detected and repaired
23
Q
What is meiosis?
A
Type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell
24
Q
How does meiosis produce genetic variation?
A
- crossover
- independent assortment of homologous pairs of chromosomes
- independent assortment of sister chromatids
25
What happens during prophase 1 in meiosis?
- DNA supercoils and becomes visible
- nuclear envelope breaks down
- spindle threads form
- homologous chromosomes join together to form a bivalent
- crossover occurs
26
What happens during metaphase 1 in meiosis?
- bivalents line up on the equator
- attached to spindles by the centromeres
- independent assortement of homologous chromosomes
- the way the chromosomes line up depends whcih pole they will be pulled to
27
What happens during anaphase 1 in meiosis?
- members of each pair of homologous chromosomes are pulled appart
- centromeres do not split
- spindle fibres contract
28
What happens during telophase 1 in meiosis?
- nuclear envelope forms around each set of chromosomes
- cell undergoes cytokinesis
29
What happens during prophase 2 in meiosis?
- nuclear envelope breaks down again
- chromosomes coil and condense
- spindle fibres form
30
What happens during metaphase 2 in meiosis?
- chromosomes line up at the equator
- spindle threads attached to the centromere
- independent assortment of sister chromatids
31
What happens during anaphase 2 in meiosis?
- centromeres divide
- chromatids of each chromosome are pulled appart to opposite poles
- chromatids are randomly segregated
32
What happens during telophase 2 in meiosis?
- Nuclear envelope forms around each of the 4 haploid cells
- cytokinesis
- chromatids uncoil and decondense
33
what is differentiation?
The process by which stem cells become specialised into different types of cells
34
What is a stem cell?
An unspecialised cell able to express all its genes and divide by mitosis
35
How are erythrocytes specialised?
- large SA:V
- flexible cytoskeleton so they can change shape
- contain no nucleus, mitochondria or ER
- biconcaved shape
36
How are neutrophils specialised?
- contain multilobed nucleus
- ingest pathogens by phagocytosis
- attracted to infection sites by chemotaxis
- contain lots of lysosomes
37
How are spermatozoa specialised?
- lots of mitochondria to provide ATP for undulipodium
- long and thin to move easily
- enzymes from the acrosome digest outer layer of the ovarum
38
How is squamous epithelial tissue specialised?
- squashed epithelial cells
- lign the alveoli
- thin
39
How is cilliated epithelial tissue specialised?
- contain no blood vessels
- short cell cycle
- protection, absorption, filtration and excretion
40
How is cartilage specialised?
- reduces friction and protective
- fibrous (vertabrae discs)
- elastic (outer ear)
- hyaline (trachea)
41
How is muscle tissue specialised?
- well vascularised
- elongated and contain myoligaments
- fibres
- skeletal, cardiac, smooth
42
How are palisade cells specialised?
- large vacuole - chloroplast are closer to the leaf surface
- many chloroplast
- little space between cells for air to circulate
43
How are root hair cells specialised?
- large SA
- carrier proteins in plasma membrane for active transport
- produces ATP for active transport
44
How are guard cells specialised?
- found in lower epidermis
- tips are more flexible
- rigid and thicker in the middle
45
How is epidermal tissue specialised?
- consists of flattened cells
- protective covering
- waxy surface
46
How is xylem specialised?
- dead hollow cells
- ligned with lignin so waterproof
- carry water up the plant
47
How is phloem specialised?
- consists of companion cells and sieve tubes
- companion cells retain orgnelles
- companion cells provide ATP for active transport
48
What does differentiation involve?
The expression of some genes and not others
49
What does totipotent mean?
- can turn into any cell including placenta
- 5 days after
50
What does pluripotent mean?
- can turn into any human specialised cell
- after 5 days
51
What does multipotent mean?
- already differentiated and can turn into groups of specialised cells
- after you have been born
52
What does potency mean?
The ability to differentiate
53
What are the uses of stem cells?
- bone marrow transplant
- testing for drug toxicity
- research parkinsons disease
