Summary OCR A-Level Biology 6.2.1 Cloning and Biotechnology
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6.2.1
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A Level Biology A for OCR Student Book
These are detailed Revision Notes for Topic 6.2.1 of OCR A-Level Biology (Cloning and Biotechnology). They were written by me using a combination of the textbook and class notes. I will also be uploading the other topics and creating bundles.
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- Natural cloning in plants
- Artif...
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Cloning and Biotechnology
22.1 Natural Cloning in Plants
22.1 natural cloning in plants
- Plants form natural clones is called vegetative propagation. The
clones are produced by mitosis from undifferentiated meristem cells. 22.2 artificial cloning in plants
22.3 cloning in animals
Type of Example Description
Vegetative 22.4 microorganisms and biotechnology
Propagation 22.5 microorganisms, medicines and
Root suckers Elm Trees Root suckers grow from the meristem bioremediation
cells in the tree trunk close to the ground
Runners Strawberry Lateral stem grows along the ground from 22.6 culturing microorganisms in the
plant the parent plant. Roots develop where the laboratory
runner touches the ground.
22.7 culturing microorganism on an
Tubers Potatoes Underground stems swell with stored food
and develop into new plants. industrial scale
Bulbs Daffodils Leaf bases swell with nutrients and buds 22.8 using immobilised enzymes
develop into new plants.
Rhizomes Marram grass Underground horizontal stem develops buds
and forms new vertical shoots.
Advantages of Natural Cloning Disadvantages of Natural Cloning
- Quick and allows organisms to reproduce rapidly - Offspring may be crowded
- All offspring have the genetics to enable them to - No genetic diversity
survive in the environment - The population will show very little variation
Can be completed if sexual reproduction is not - Selection by environmental problems is not
possible or fails possible
- Reproduction can happen with only one parent Detrimental changes in the environment will
affect all of the population
- Many houseplants are propagated by taking cuttings. Sections of stem are taken and planted; rooting
hormones is often applied to the base of the cutting to encourage root growth.
22.2 Artificial Cloning in Plants
- Micropropagation makes large numbers of genetically identical offspring from a single parent using a
tissue culture technique.
- It is usually used if the plant does not produce many seeds, doesn’t respond well to natural cloning, is
rate, had been genetically modified or is required to be pathogen free.
- Steps of micropropagation:
o A small sample of meristem tissue is taken from shoot tips. The tissue removed is called an
explant. This is done in sterile conditions to avoid contamination from fungi or bacteria.
o The explant is sterilised (in ethanol or sodium dichloroisocyanurate).
o The sterilised explant is placed in a culture medium containing plant hormones such as auxins
that stimulate mitosis.
o The explant cells divide to form a mass of undifferentiated cells called a callus.
o The callus is transferred to a new culture medium, which contains hormones that encourage
differentiation and shoot growth.
o The developing plantlets are transferred into soil.
Advantages of Micropropagation Disadvantages of Micropropagation
- Rapid production of large numbers of plants - High cost and labour intensive, it is highly
- Produces disease free plants skilled work with specialised equipment.
, - Possible to produce viable numbers of plants after the genetic - Sterile conditions must be maintained
modification of plant cells. - Produces a monoculture so the population is
- Provides large numbers of new plants that are sterile and susceptible to diseases
seedless to meet consumers demands - Explants and plantlets are vulnerable to
- Provides a way of growing plants that are difficult to grow infection by moulds or other diseases during the
from seed. production process.
- A way of reliably increasing the numbers of rare or endangered - If the explant is infected with a virus, all of
plants. the clones will also be infected.
- Little space needed for tissue culture
- Tissue culture can happen any time of year
22.3 Cloning in Animals
- Natural cloning in animals occurs in identical twins, a zygote splits into two to produce two genetically
identical offspring.
- Many invertebrates produce clones.
o Crayfish can regenerate an entire organism from just a fragment of the original.
o Sponges and flatworms create clones as a part of their natural reproductive system.
o Hydra produce small buds on the side of their bodies that eventually live independently.
Artificial Embryo Twinning:
- Artificial embryo twinning process:
o Sperm from a male with desired traits is used to fertilise eggs from a desired female via
artificial insemination.
o The zygote divides by mitosis to form a ball of cells.
o At around day 6 when the cells are still totipotent, the cells are separated and allowed to
continue dividing in the lab.
o Each mass of cells grows into an embryo and is implanted into a surrogate mother.
Somatic Cell Nuclear Transfer:
- Somatic cell nuclear transfer process:
o The nucleus is removed from a somatic cell of an adult animal and the nucleus is removed
from a mature egg cell.
o The nucleus from the somatic cell is placed into the enucleated ovum and given an electric
shock so it fuses and begins to divide.
o The embryo is transferred into a surrogate mother.
- This process is known as reproductive cloning
Advantages of Artificial Cloning in Animals Disadvantages of Artificial Cloning in Animals
- Desirable genetic characteristics always passed on - Very difficult to do, time consuming and
- Infertile animals can be produced expensive
- Do not need to wait for breeding season - No genetic variability – all susceptible to the
- Increases the population of endangered species same disease
- Develops new treatments for disease - Undesirable characteristics always passed on
- Produces more offspring than normal reproduction - Clones may not live as long as natural
- Allows genetically modified embryos to be replicated. offspring or have health problems
- Can clone specific animals, e.g., top racehorse
22.4 Microorganisms and Biotechnology
- Biotechnology is the exploitation of organisms and biological processes in industry, food science,
agriculture, or medical science.
- Most biotechnology uses enzymes in the form of a whole microorganism such as bacteria or fungi.
- There are many benefits of using microorganisms:
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