chapter 2: cell cycle Flashcards
1
Q
what is binary fission
A
asexual reproduction in prokaryotes, the division of a prokaryotic cell to form 2 cells
2
Q
steps in binary fission
A
- the chromosomes replicate and the cell elongates
- the chromosomes move to opposite ends
- the plasma membrane pinches and a septum forms
- the septum extends AND SPLITS
- 2 genetically identical daughter cells form (clones)
3
Q
what is the eukaryotic cell cycle
A
- the life of a cell
- includes replication - mitosis
4
Q
explain the G1 (gap 1) phase
A
- the cell grows, increasing the cytosol
- cells synthesise proteins for DNA replication
- mitochondria and chloroplasts divide
- the cell commits to continue with the cell cycle or not
5
Q
explain the G0 phase
A
- if the cell doesn’t continue into the cycle, it goes into the G0 stage
- the cell carries out its normal function
- often temporary- so they normally re-enter g1
- some specialised cells remain permanently in G0 phase (nerve cells)
6
Q
explain the synthesis (s) phase
A
- parent cell replicates its DNA
- by the end of this stage, the cell has 2 identical copies of each chromosome (called sister chromatids) joined at the centromere
7
Q
explain the G2 stage
A
- the secondary stage of growth- prepares for mitosis
- acquires energy, grows and synthesised proteins
- by the end of interphase, the cell has doubled in size and DNA
8
Q
explain mitosis
A
the division of the nucleus
9
Q
prophase
A
- chromosomes condense (become shorter and thicker)
- nuclear membrane breaks down
- centrioles move to opposite poles
- spindle fibres extend BETWEEN THE poles
10
Q
metaphase
A
- the sister chromatids attach to the spindle fibres by the centromere
- chromosomes line up along the equator of the cell
11
Q
anaphase
A
- centromere divides
- each sister chromatid is pulled back to OPPOSITE pole through the contraction of the spindle fibres
12
Q
telophase
A
- nuclear membrane forms around the two groups of chromosomes
- the chromosomes decondenses (become longer and thinner)
- SPINDLES DISAPPEAR
13
Q
cytokinesis
A
- FINAL STAGE OF CELL CYCLE
- the cytosol divides INTO TWO CELLS
- the organelles redistribute around the nuclei
- in animal cells, the cell membrane pinches and forms two separated daughter cells
- in plant cells, a cell plate forms which extends to form a cell wall and two separate daughter cells
14
Q
why is the cell cycle regulated and how
A
- it is regulated to ensure that complete and damage-free chromosomes are transmitted to daughter cells
- if there is an error, the cell cycle is aborted or delayed, allowing time for the error to be corrected
15
Q
G1 checkpoint
A
- checks DNA before division
- if DNA is damaged or incomplete, the cell is stopped from continuing in the cell cycle
- it either enters G0 or is targeted for destruction through apoptosis (DNA is checked by the p53 protein (which is made by the p53 gene) - tumour suppressor protein)
16
Q
G2 checkpoint
A
- the replicated DNA is checked for completeness and lack of damage
- if it is complete and has no damage, then it continues in the cell cycle
17
Q
M checkpoint
A
- occurs during metaphase
- checks that sister chromatids are attached to the correct spindle
- ensures the sister chromatids are pulled to opposite directions
- if there is an error the cell cycle is delayed until it is fixed
18
Q
what is apoptosis
A
programmed cell death
19
Q
what does apoptosis target
A
- targets cells at the end of their natural life (DNA gets damaged easily)
- dysfunctional, damaged or diseased cells
- excessive cells
20
Q
why does apoptosis occur
A
apoptosis occurs in order for healthy body functioning
21
Q
steps in apoptosis
A
- cell receive an intrinsic signal from the cell or extrinsic signals from an exterior source
- sets off a biochemical pathway
- the cell shrinks and its contents, like organelles, break down
- blebbing occurs, forms blebs, protrusions in plasma membrane which then form apoptotic bodies
- apoptotic bodies form containing dying organelles and parts
- phagocytosis occurs - vesicles are engulfed by macrophages
22
Q
disruptions that occur in the cell cycle
A
occurs when the rate of cell production exceeds that of cell loss - build up of cells
- mutations in proto-oncogenes and anti-oncogenes lead to disruptions in the cell cycle
23
Q
proto-oncogenes
A
signal the cell to continue dividing
24
Q
tumour suppressor genes (anti-oncogenes)
A
signal the cell to stop dividing (responsible for apoptosis)
25
deviant cell behaviour
occurs when the regulation of the cell cycle fails
26
how do malfunctions in apoptosis cause cancer (DCB)
- cell cycle becomes uncontrolled, cancerous tissues have cells that reproduce too quickly forming tumours
- the genes that normally control cells during the cell cycle have been changed through a mutation
- damaged proto-oncogenes lead to too much division
- anti-oncogenes (tumour suppressor genes) lead to not enough apoptosis
- cancer cells ignore signals to undergo apoptosis due to damaged p53 gene (responsible for telling cells to stop dividing)
- checkpoints are overridden - nor error detection nor error correction occurs
- abnormal cells with damaged DNA passes their ERRORS to their daughter cells
- Parkinsons and Alzheimers are caused by too much apoptosis
27
five principles of ethics
- respect
- non-maleficence
- beneficience
- justice
- integrity
28
ethics: respect
free to make their own choices without pressure from others
29
ethics: non-maleficence
- do no harm
- risks and damage needs to be minimised
- benefits outweigh risk
30
ethics: beneficience
- do good for all
| - ensure and increase patient's benefit
31
ethics: justice
- equal access to treatment
- considers how resources should be distributed
- the existence of research and the right motive to research
32
integrity
- doing the right thing
- stem cell therapy follows the principle integrity because it can potentially cure diseases when nothing else can so it is the right thing to do for humans
33
stakeholders
can groups or individuals who can affect situations or are affected by it
34
what are stem cells
undifferentiated/unspecialised cells that have the ability to differentiate into other types of cells
35
what is specialisation
a structure being able to carry out specific functions efficiently
36
cell differentiation
the process of becoming specialised for a specific function
37
what happens when a stem cell divides
- when a stem cell divides, they produce:
- a specialised differentiated cell
- an a replacement stem cell (self-renewal)
38
what is the potency of a cell
the ability to produce different cell types
39
totipotent
- potential to give rise to all or any cell types
| - eg. zygote (fertilised egg cell), embryonic cells of two, four or eight celled
40
pluripotent
- can differentiate into many cell types (except the placenta cells)
- eg. embryonic stem cells from the inner mass of a blastocyst (early embryo) (ES)
41
multipotent
- stem cells that can differentiate into a closely related family of cells - cells of similar types
- eg. blood stem cells can turn into different types of blood cells (ADULT SOMATIC CELLS)
42
unipotent:
- only have the ability to differentiate into cells of their own type and can still self renew
- eg. muscle cells
43
sources of stem cells
- embryonic stem cells
- induced pluripotent stem cells (iPSCs)
- adult/somatic stem cells
44
embryonic stem cells
- inner mass of blastocyt
- single cell is isolated and grown in a culture
- divides by mitosis producing culture of stem cells
- obtained from extra embryos created from IVF by destroying the embryos (ethical issues)
- pluripotent
45
induced pluripotent stem cells (iPSCs)
- specialised adult somatic cells can be genetically reprogrammed (induced) to return to an undifferentiated embryonic state
- achieved by adding 4 embryonic genes
- pluripotent
46
adult/somatic stem cells
- obtained from various sources of adult tissues (bone marrow, cord blood, brain)
- are multipotent
47
blastocyst
early embryo
