1.4 Cellular Differentiation Flashcards
What is differentiation?
a basic unspecialised cell becomes altered to have a specific structure and function through the expression of certain genes
TOPTIP
Differentiation = Specialisation
What is gene expression?
the transcription and translation of genes to produce proteins
Expression of Essential genes?
essential genes that code for proteins vital to all cells e.g. respiratory enzymes are ‘switched on’ - expressed
Expression of cell specific genes?
cell specific genes that code for proteins allowing the cell to specialise to perform a function are ‘switched on’ - expressed
Expression of unnecessary genes?
Unnecessary genes to the function of the particular cell are ‘switched off’ - not expressed
TOP TIP
specialised cells can be somatic (body cells) or gametes (sex cells)
LOOK AT DIAGRAM
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TOP TIP
When writing about specific genes being ‘switched on’ and others being switched off make sure you dont refer to a gene as being switched on and off - it gives the wrong idea completely
What are meristems?
undifferentiated cells dividing by mitosis are found in specific regions of a multicellular plant called meristems
meristems are the only places that growth can occur in multicellular plants
cells produced in meristems then become specialised to form differentiated tissue
What is totipotent?
meristematic cells are said to be totipotent which means they can form all the types of differentiated cells of the organism
What are the two types of meristems?
apical
lateral
What are apical meristems?
an apical meristem is found at the apex or tip of the roots and shoots of a plant
the growth and increase in length of the roots and shoots depends on three cells dividing, elongating, and becoming specialised for a particular function
zones of a root tip?
root cap - protects the root as it forces its way downwards through the soil particles
zone of cell division - meristem - where new cells are formed
zone of elongation - the cells stretch and vacuoles form
zone of specialisation
How do you calculate the mitotic index?
no. of cells undergoing a stage of mitosis
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no. of cells in field of views
What are annual plants?
annual plants complete their life cycle in one year and then they die. They do not need particularly thick stems to support the plant as the plant will not grow very tall in one year.
What are perennial plants?
perennial plants grow year after year and must develop thicker stems in order to support the new growth each year
this increases in girth of the plant is produced by lateral meristems
What are lateral meristems responsible for?
responsible for making sure that enough new xylem is formed so that the plant gets enough support and is able to transport enough water and minerals to the living parts of the plant
How are annual rings formed?
xylem is produced every year leading to the formation of annual rings
Size of annual rings
spring into summer?
summer into autumn?
spring into summer - large thin walled xylem vessels allow for increased flow of water + minerals
summer into autumn - small thick walled xylem provide greater support
what is the width of each ring dependent upon growing conditions present during that year?
a) wider rings produced by warm or wet weather
b) narrow rings are produced by cold or dry conditions
What is mericloning?
plants such as orchids can be cloned by a process called mericloning
this involves removing the shoot tip of a parent plant containing the meristem
the cells are cultured in laboratory and grown into new plants
the plants produced by mericloning are identical to the parent plant from which the meristem cells were taken
this process allows many copies of a desirable plant to be produced.
What is tissue culture?
the growth of tissues or cells separate from the organism
meristem is a type of plant that would be useful in tissue culture
Where are the two locations of meristematic regions in a plant?
root and shoot tips (apical)
cambium between xylem and phloem in vascular bundles (lateral)
How do scientists use tissue culturing techniques to create a clone of a plant?
tiny pieces of plant tissues are cut from the parent plant and grown on a medium containing nutrients and growth regulators (plant hormones) in aseptic conditions (free contamination)
The cells multiply and form a mass of undifferentiated cells called callus
in the presence of the correct balance of hormones in the growth medium, the callus tissue differentiates into plantlets with roots and shoots
when these plantlets are transferred to potting compost, they develop into normal, complete plants
thousands of genetically identical offspring (clone) can be obtained from a single plant by subdividing the calluses as they grow
What can tissue culturing of plants used for?
production of clones of commercially important plants such as ornametals e.g. rose and orchid, crops including pineapple and oil palm and forests e.g. pine trees
regeneration of transgenic plants following genetic modification
Multiplication of plants that have been cleared of pathogens, for use in horticulture and agriculture
What is a stem cell?
A stem cell is a master cell that is found in multicellular organisms
they are undifferentiated and have a unique property in that they can not only make new copies of themselves (self renewal) but can differentiate to become a specific cell type
What are embryonic stem cells?
are totipotent - have the potential to become any type of body cell.
What are the two sources of stem cells?
embryonic and adult tissues
What are sources of stem cells?
donated embryos
amniotic fluid
induced pluripotent stem cells
Donated embryos?
patients undergoing infertility treatment may agree to donate any extra embryos that are not required for their treatment to medical science
these very early embryos proved an immediate source of embryonic stem cells from donated embryos
these sources are limited, restricting the research that can be done on embryonic stem cells
Amniotic fluid?
stem cells can be harvested from the fluid removed from pregnant women for amniocentesis tests
the stem cells obtained are multipotent the advantage is that no human embryos are destroyed in this procedure
Induced pluripotent stem cells?
induced pluripotent stem cells are not true stem cells. they are differentiated cells that have been genetically reprogrammed using transcription factors to switch some of their switched off genes back on again
as a result they act as stem cells and can be used for research
Moral ethical issues?
unused blastocysts from embryonic stem cells lines and cytoplasmic hybrid cells are destroyed as they are not allowed to develop beyond day 14 of the development stage. this is when the embryo would normally implant in the uterus and develop into a foetus.
Health ethical issues?
a complete medical history of adult stem cell donors is required to minimise the chance of recipients developing other medical problems
Safety ethical issues?
stem cells must be safe to use in the treatment of patients i.e. they should not cause other conditions or diseases such as tumours caused by certain types of IPSCs. It is for this reason that ongoing research and thorough testing is vital.
What are therapeutic uses of stem cells?
New skin can be grown in the laboratory from the stem cells of burns patients for grafting
As the new skin has been grown from the patients own stem cells, it will not be rejected by the body
Bone marrow transplants give patients suffering from cancer of the blood (leukemia) the ability to make healthy blood cells from the stem cells within the donated bone marrow
Corneal transplants in the eye can be achieved by growing new corneal tissue from a patients eye stem cells which replaces damages cornea, restoring light.
