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
- ————————————————————-
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)
