Cloning and biotechnology Flashcards
Clones
-Genetically identical copies of organisms/cells
-Produced asexually in which the nucleus is divided by mitosis
How are clones produced by mitosis
-Mitosis creates two genetically identical copies of the DNA
-The DNA is separated into two genetically identical nuclei
-Before the cell divides and creates two genetically identical cells
Why may the cells produced by mitosis not be identical
May not be physically/chemically identical as after division they may differentiate to form two different types of cell
How does yeast/ bacteria reproduce
Asexually by budding
Asexually by binary fission
Advantages of natural cloning
-If conditions of growth is good for the parent it will be good for the offspring
-Cloning is rapid so population can reproduce quickly to take advantage of the suitable environment conditions
-Reproduction can be carried out when sexual reproduction may not be possible
Disadvantages of natural cloning
-Offspring may become over crowded
-No genetic diversity ( except from mutations in the DNA)
-Population shows little variation
-Selection is not possible
-If environment changes to be less advantageous, the whole population is susceptible
Vegetative propagation
Natural cloning
Reproduction from vegetative parts of the plant - usually an over wintering organ rather than through specialised reproductive structures
Plant cloning
Differentiation of many plant cells is not as complete as in animals many parts of the plant contain cells with the ability to divide and differentiate into other types of cell
Examples of plant cloning by vegetative propagation
-Runner/ stolens/ rhizomes/ suckers
-Bulbs
-Corms
-Leaves
-Runners/ stolens / Rhizomes
Plants that grow horizontal stems that can grow roots at any point
-Grow on the surface of the ground (Runners/ stolens)
-Grow under ground (Rhizomes )
How are some Rhizomes adapted
Adapted as thickened overwintering organs from which one or more new stems will grow in the spring
Suckers
New stems that grow from the roots of the pant - may be close to the base of the older stem/ some distance away
-Original horizontal branch will die and leave the new stem as a separate individual
Bulbs
e.g. onions
-Overwintering mechanism
-Consists of an underground stem which grow a series of fleshy leaf bases
- Also an apical bud that will grow into a new plant in the spring
-Often bulb contains more than one apical bud and each will grow into a new plant
Corms
-Solid rather than fleshly like a bulb
-Underground stem with scaly leaves and buds
-Remain in the ground over winter
-In spring the buds grow to produce one or more plants
Leaves
Kalanchoe plant reproduces asexually as clones grow on the leaf margins
-Immature plants drop off the leaf and take root
Tubers
Another type of underground stem i.e. potatoes
-One potato will grow into one/more plants
-Each new plant can produce many new tubers (potatoes) later that year
Cloning in animals
Don’t clone as often as plants but there are some e.g. of natural cloning i.e. identical twins
How do identical twins form
Fertilised egg (zygote) divides as normal but the two daughter cells split to become two separate cells
-Each cell grows and develops into a new individual
What is the easiest way gardeners/growers make clones
Cuttings
-A stem is cut between the nodes
-Cut end of the stem is placed in moist soil
-New roots will grow from the tissue in the stem - usually from the node but may grow from other parts of the buried stem
What helps stimulate root growth from cuttings
Dipping the cut stem in rooting hormone / remove the bark from the cut end of the stem as this encourages the plant to produce a callus
Where else can a cutting be taken from a plant
-Root cuttings = section of the root is buried just below the soil surface and produces new shoots
-Scion cuttings = dormant woody twigs
-Leaf cuttings = leaf placed on moist soil ; leaves develop new stems and roots
What are the disadvantages of taking cuttings for natural cloning
Large scale cloning can be time time-consuming and take a lot of space
-Some plants don’t respond well to cuttings
Tissue culture
Growing new tissues, organs, plants from certain tissues cut from the sample plant
-Alternative to taking cuttings
-Carried out on a nutrient medium under sterile conditions
-Application of plant growth substances at the correct time can encourage the cells in the growing tissues to differentiate
What is tissue culture most used for
commercially used to increase the number of new plants in micropropagation