Cell division and stem cells

  • Created by: Emily.T
  • Created on: 05-05-17 19:29
What is the cell cycle?
It is the process of cell growth and division that all cells in multicellular organisms use to grow and divide
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What are the 4 stages in the cell cycle?
Growth phase 1 (G1), Growth phase 2 (G2), Synthesis phase (S), and Mitosis (M)
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What happens at each stage of the cell cycle?
G1 - cell grows, new organelles and proteins are made, S - cell replicates its DNA ready to divide by mitosis, G2 - cell keeps growing and proteins needed for cell division are made, M - mitosis and cytokinesis
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What happens at the G1 checkpoint?
The cell checks for: cell size, nutrients, growth factors and DNA damage
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What happens at the G2 checkpoint?
The cell checks for: cell size, DNA replication, DNA damage
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What stages are known as together as the 'interphase' part of the cell cycle?
The G1, S & G2
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What is mitosis needed for and what does it produce?
Growth of multicellular organisms, repairing damaged tissues, asexual reproduction and produces 2 genetically identical daughter cells (to the original)
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What happens in interphase?
Cell carries out normal functions while preparing to divide, DNA unravelled and replicated, to double genetic content, the organelles are replicated too and ATP content is increased
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What are the 4 division stages in mitosis?
1) Prophase 2) Metaphase 3) Anaphase 4) Telophase
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What happens in Prophase?
- chromosomes condense, - centrioles go to the poles, - spindle fibres form, - nuclear envelope breaks down
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What happens in Metaphase?
- chromosomes line up in the middle (along the metaphase plate) and attach to spindle by their centromere and held in position
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What happens in Anaphase?
- centromeres divide separating the pair of sister chromatids as the spindle firbres contract and shorten causing the chromatids to be pulled to opposite poles of the cell (centromere first)
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What happens in Telophase?
- chromatids reach opposite poles, - chromatids uncoil and are now chromosomes again, - nuclear envelope reforms around each group of chromosomes, - are two nuclei
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What is cytokinesis?
Cytokinesis is the division of the cell's cytoplasm dividing to form 2 genetically identical daughter cells, a cleavage furrow is formed when the cytoskeleton pulls the membrane inwards
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What happens in the division of plant cells?
Vesicles from the Golgi body begin to assemble where the metaphase plate was. Vesicles fuse with each other and the c-s mem. dividing the cell into 2. New sections of cell wall then form along new membrane sections
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What is meiosis needed for?
To produce haploid cells, produce gametes, a reduction division, genetic variation, sexual reproduction
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How many stages does meiosis have?
Two - meiois | (1) and meiosis || (2)
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What happens in prophase 1 in meiosis?
- chromosomes condense and arrange themselves in homologous pairs (form bivalent pairs), - crossing over occurs, - centrioles move to the poles, - spindle fibres form, - nuclear envelope breaks down
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What happens in metaphase 1 in meiosis?
- homologous (aka bivalent pairs) line up on the metaphase plate, - centromeres attached to the spindle fibres, - random assortment occurs
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What happens in anaphase 1 in meiosis?
- spindles contract and shorten, - homologous pairs separate so one chromosome goes to each pole (end) of the cell
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What happens in telophase 1 in meiosis?
- chromosomes assemble at poles, - nuclear envelope reforms around each group of chromosomes, - chromosomes uncoil, - cytokinesis occurs and cell goes from diploid to haploid
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What happens in meiosis 2?
Meiosis 2 is the same as mitosis but 4 genetically different daughter cells are produced (where variation is increased by crossing over and random assortment)
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What is crossing over?
It's where homologous pairs of chromosomes come together and when they pair up the chromatids twist around each other and parts of the chromatids break off and swap over, so the chromatids still contain the same gene, but different allele combination
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What does crossing over and random assortment do?
Increase genetic variation
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What is random (independent) assortment?
The random alignment and positioning of chromosomes during metaphase 1, causing the 4 daughter cells to have completely different combinations of the maternal and paternal chromosomes from each other
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Where are stem cells found in humans?
In early embyo's - embryonic stem cells, and in adults in the bone marrow
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Can adult stem cells differentiate into any type of cell?
No they are only able to differentiate into any type of blood cells
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Can embryonic stem cells differentiate into any type of cell?
Yes they can!
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What are stem cells?
Unspecilaised cells that have the potential to differentiate into any different types of cell
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What are stem cells used for?
Regeneration of cells, repairing damaged cells/tissues, treatment of neurological conditions, research into developmental biology
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What does totipotent mean?
Able to differentiate into any type of cell and produce a whole organism (embryonic stem cells can do this)
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What does pluripotent mean?
Able to differentiate into any type of cell
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What does mulitpotent mean?
Able to differentiate into a range of cells within a tissue, e.g. adult stem cells in the bone marrow can only develop into different types of blood cells - used to treat Leukemia
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Why do red & white blood cells need continuously replacing?
Because erythrocytes (essential in oxygen transport) lack a nucleus and organelles so they cannot reproduce & have a short life span of around 120 days, neutrophils (essential role in immune system) have a life span of around 6 hours
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Sources of: Embryonic stem cells
Present at a very early stage of embryo development, are totipotent, after around 7 days a mass of cells (blastocyst) has formed and cells are in a pluripotent state, remain in this state in the fetus until birth
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Sources of: Adult stem cells
Present throughout life from birth, found in bone marrow, are multipotent (can be artificially triggered to become pluripotent), can be harvested from umbilical cords at birth
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What are the advantages of using adult stem cells?
There is a plentiful supply of umbilical cords so invasive surgery is unessecary (-ve need parents permission), tissues cultured from these stem cells would not be rejected in a transplant to the umbilical's owner, can be stored for future use
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What diseases/conditions can stem cells be useful for treatment?
Heart disease, Type 1 diabetes, Parkinson's disease, Alzheimer's disease, Muscular degeneration, Birth defects and Spinal injuries
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What diverse areas can stem cells be used in?
Treatment of burns, Drug trials and devleopmental biology
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How can stem cells be used in the treatment of burns?
Stem cells grown on bio-degradable meshes that can produce new skin for burn patients - a lot quicker than grafting
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How can stem cells be used in drug trials?
Potential new drugs can be tested on cultures of stem cells acting as a particular tissue before being tested on animals and humans - could reduce the use for animal testing to an extent
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How can stem cells be used in developmental biology?
This is the study of changes that occur as multicellular organisms grow and develop from a single cell and why things sometimes go wrong - so with their ability to divide indefinitely and differentiate into any type of cell this is very useful
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What are the ethical issues in using embryonic stem cells?
Destruction of a potential life, religious and moral objections = murder, lack of consensus (agreement) as to when embryo itself has rights and who owns the genetic material, need to respect and value life,
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What recent law in the UK has arisen regarding the source of stem cells?
The law states that embryos can be specfically created in the lab as a source of stem cells to stop using the donated onces left over from fertility treatment
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What problems do the ethics cause in terms of the research devleopment?
They hold back the progress that could lead to successul treatments of many incurable diseases
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What are the problems with using adult stem cells?
Even though they are a good alternative to embryonic, they do not divide as well as umbilical stem cells and are more likely to have acquired mutations
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What is currently being done to reduce the usage of embryonic stem cells?
Developments are being made towards artificially transforming tissue stem cells into pluripotent cells - Induced pluripotetn SC's (iPSC's) are adult SC's that have been genetically modified to be pluripotent (like embyonic SC's)
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What is the limitation of using umbilical stem cells?
They are only multipotent and not pluripotent so they restrict their usefulness
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What are Islam's views on the use of embryonic stem cells?
They believe the soul is "breathed in" to the human embryo on the 40th day after fertilisation & this is when life becomes sacred. Islam accepts the fetus is accorded the status of a legal person only at later stages of its development
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What are Roman Catholic's, Orthodox & conservative Protestant churches views on the use of embryonic stem cells?
Since a human embryo is believed to have a status of a human individual from the moment of the fertilisation, it has the right to its own life, and every intervention not in favour of the embryo is a violation of that righ
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What are Judaism's view on the use of embryonic stem cells?
Emphasise the importance of the saving of life & considers the ultimate goal of embryonic SC research to be life saving. Fetus less than 40 days old & the pre-implanation embryo does not have a full human status, after 40 considered part of women
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How can stem cells help with the treatment of Alzheimer's diseas?
Nerve cells in the brain die in increasing numbers. This results in severe memory loss. Researches are hoping to use stem cells to regrow healthy nerve cells in people with Alzheimer's
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How can stem cells help with the treatment of Parkinson's disease?
Patients suffer from tremors they can't control. Disease causes loss of a particular type of nerve cell found in the brain. These cells release dopamine needed to control movement. Tranplanted stem cells may help regenerate dopamine producing cells
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What are the sources of plant stem cells?
The meristem tissue - found wherever growth is occuring, such as the tips and shoots = aplical meristems - meristem tissue located between phloem & xylem tissues = vascular cambium
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What cells can the stem cells present in the meristem tissue of a plant differentiate into?
Can differentiate into different cells present in xylem and phloem tissues - vascular tissue grows as plant grows - pluripotent nature of the SC's in the mertistems continues throughout life of plant
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Stem cells are a....
Renewing source of undifferentiated cells
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Card 2

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What are the 4 stages in the cell cycle?

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Growth phase 1 (G1), Growth phase 2 (G2), Synthesis phase (S), and Mitosis (M)

Card 3

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What happens at each stage of the cell cycle?

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Card 4

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What happens at the G1 checkpoint?

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Card 5

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What happens at the G2 checkpoint?

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Comments

LAZIBA

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Thank you.Amazing help. REALLY RECOMMEND THIS! <3

Yoongililphoenix

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why does card 42 feel like the future answer to immortality? what a waste of childrens blood. lol

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