Most of a cell’s DNA is not translated Flashcards
What is a zygote?
- a fertilised egg cell
What is a blastocyst?
- a zygote that has divided repeatedly to form a ball of cells
Define cell differentiation
- the process by which each cell develops into a specialised structure suited to the role that it will carry out.
What are stem cells?
- undifferentiated cells that can become specialised
How can stem cells become specialised?
- selective expression/silencing of certain genes, meaning that only part of the cell’s DNA is translated into proteins.
Define gene silencing
- Switching off genes preventing expression via a) preventing transcription and/or
b) breaking down mRNA before it can be translated
What could heart muscle cells be used to treat?
- Heart damage e.g. result of a heart attack where lack of oxygen has caused cell death
What could skeletal muscle cells be used to treat?
- Muscular dystrophy
What could the beta cells of the pancreas be used to treat?
- Type I diabetes (beta cells produce insulin)
What could nerve cells be used to treat?
- Parkinson’s
- multiple sclerosis
- strokes
- Alzheimer’s disease
- spinal injury paralysis
What can blood cells be used to treat?
- leukaemia, blood diseases
What can skin cells be used to treat?
- burns and wounds
What can bone cells be used to treat?
- osteoporosis
What can cartilage cells be used to treat?
- osteoarthritis
What can retinal cells be used to treat?
- macular degeneration
What are totipotent stem cells?
- undifferentiated dividing cells found in animal tissues
Totipotent cells (best)
- Cells produced from the division of the zygote for up to 5 days after fertilisation (embryonic stem cells).
- Can differentiate to become any cell type. During development, totipotent cells transcribe and translate only part of their DNA
Pluripotent cells (2nd)
- Cells of the inner cell mass in the blastocyst (includes embryonic stem cells and foetal stem cells)
- Have the potential to create every cell in the body but the placenta
- Placental stem cells found solely in the placenta develop into specific cells.
Multipotent cells (3rd)
- Pluripotent cells that have become further specialised, e.g. adult stem cells and umbilical cord blood stem cells. (adult stem cells found
throughout body tissues of the foetus, through to the adult help maintain and repair tissues of
specific organs they are located in) - Give rise to a limited number of other cells e.g. hematopoietic cells in bone marrow producing red and white blood cells, and platelets
Unipotent stem cells (worst)
- Only differentiate into one type of cell e.g. cardiomyoblasts differentiating into cardiomyocytes (cardiac muscle cells)
- Come from multipotent stem cells and are made in adult tissue
Why not just use adult stem cells (instead of embryonic)?
- Limited use in research as they are further along the specialisation pathway
- Often contain DNA damage due to ageing, toxins, and random DNA mutation
- Scientists have not yet identified cells for every type of mature body cell
- Takes time to mature in culture to produce adequate numbers for treatment
- Often only in minute quantities, and numbers usually decrease with age
What are induced pluripotent stem cells?
- Genetically altered unipotent cells - to make them acquire characteristics of pluripotent
embryonic stem cells. Produced artificially from adult somatic (body) cells by ‘switching genes on’ using protein transcription factors
What are the benefits of induced pluripotent stem cells?
- capable of self-renewal so could divide indefinitely to provide a limitless supply (could replace embryonic stem cells)
- iPS cells are genetically identical to cells of the somatic cell donor - prevents immune rejection of foreign tissue if the donor is also the patient.
Could you use red blood cells to make iPS cells?
Explain your answer.
- No;
- Because red blood cells do not have a nucleus
Points for the use of embryonic stem cells
- Can be injected into damaged tissues to repair them e.g., retina
- Argument at this embryonic stage, a ‘human life’ isn’t fully formed
- Wrong to allow humans to suffer when there is a way to alleviate it.
- Embryos are produced for fertility treatments, so spares can be used for research instead of destroying them.
- Adult stem cells less effective and limited in what they specialise into
Points against the use of embryonic stem cells
- Argument that an embryo is a human life with rights - shouldn’t be experimented with, even with potential to cure diseases.
- Scientists should find other sources of stem cells, or just use adult ones
- If stem cells don’t respond properly once inserted, they can lead to cancer if dividing uncontrollably.
- Stem cells grown in a lab can get contaminated with a virus
