Cloning & Biotechnology (OCR A Level Biology): Flashcards

• Tubers are swollen modified structures that form eyes on their surface

• The eyes sprout new growth (called 'chitting')

• Starch stored in the tuber fuels the early growth of the new plant

A modified stem that grows horizontally underground (e.g. ginger). New stems and adventitious roots grow from its nodes.

Growths that appear from the root systems of trees and shrubs, providing meristematic tissue (e.g. poplars, cherries, plums).

It allows them to propagate desirable species asexually, effectively and at less cost than using sexual reproduction techniques, e.g. by taking cuttings and dividing plants into clumps or sections.

Small, virtually complete daughter plants produced asexually on the mother plant (e.g. tulips, lilies).

False — no other DNA is introduced, so the offspring are genetically identical clones.

True

A section of stem cut from a parent plant that is encouraged to grow adventitious roots, developing into a new, full-sized plant.

It is a straightforward propagation technique that can expand plant stock at very low cost.

Roots that grow from an unusual position on the plant, such as from a cut stem, rather than from an existing root system.

Many perennials, shrubs and herbs can grow adventitious roots from their cut stems.

Because propagation by cuttings is a form of asexual reproduction, the offspring are genetically identical to the parent.

This means the desirable characteristics of the parent are guaranteed in the progeny.

• Desirable characteristics of the parent are guaranteed because it is asexual reproduction

• Plant stock can be expanded at very low cost

• Cuttings grow to full-sized plants much quicker than plants grown from seeds

Cuttings grow to full-sized plants much quicker than plants grown from seeds.

• Sharp scissors or secateurs

• Potting compost

• Pots to house the new plants

• Hormone rooting powder

• Plastic bag to cover the cutting

Hormone rooting powder contains auxins.

Hormone rooting powder contains auxins that promote mitosis and cell differentiation in new root growth.

If the cut is made just below a stem node, meristem tissue forms at the lower end of the cut.

This tissue can divide and differentiate to produce the new adventitious roots.

Tissue containing unspecialised cells capable of dividing by mitosis; in a cutting it forms at the lower end of the cut and gives rise to new root growth.

Covering the cutting with a plastic bag reduces water loss by transpiration, keeping the cutting in a humid environment while it establishes new roots.

The auxins promote mitosis and cell differentiation in the new root growth.

True

False — cuttings grow to full size much quicker than plants grown from seeds.

A strain of genetically identical plants (a clone) produced artificially, which can endure as foodstuffs or commercial blooms for many years.

A small piece of a plant that is cut off and grown into a new clone of the original plant.

The ability of a cell to divide and differentiate into all the different cell types that make up a complete organism. Many plant cells are totipotent, unlike animal cells.

They harness the natural processes of vegetative reproduction, using techniques such as:

• Cuttings

• Layering

• Grafting

• Division

• Budding

The formation of meristematic tissue, from which plant organs can differentiate.

Many plant cells are totipotent, meaning an entire plant can be reproduced from any one of these cells.

Because it is comprised mostly of actively dividing cells and can withstand being handled.

To avoid fungi from colonising the growth medium, which would cause the micropropagation to fail (fungal growth would be seen rather than explant growth).

• Break off a small floret of cauliflower and use a scalpel to cut a thin section (about 5–10 mm long) — this is the explant

• Sterilise the explant by soaking it in sterilising solution for 15 minutes, swirling it every 5 minutes

• Use sterilised forceps to transfer the explant onto agar growth medium containing a sterilant

• Leave the container on a sunny windowsill for around 3 weeks

It provides all the nutrients the plant needs for growth, and contains a sterilant to ensure no contamination occurs throughout the experiment.

That the cells in the explant have the capability to produce all the different cell types that make up a full cauliflower plant — i.e. they are totipotent.

• Reproducing endangered species of plants where relatively little source material exists

• Producing clones in large numbers for distribution to commercial growers and garden centres

True

False — they prevent fungi from colonising the growth medium, which would otherwise cause the micropropagation to fail.

Because they all have the same genotype, so they show the same characteristics (phenotype).

Any three of:

• The plants are free of disease

• They can be genetically modified to confer immunity to certain diseases

• The process is rapid and yields large numbers of new plants

• The small plants can be transported easily to other sites

• Plants that are difficult to grow from seed can be produced

It allows growers to ensure that plants carry very distinct characteristics, and it can confer immunity to certain diseases.

Rare and endangered species can be propagated by cloning to save them from extinction.

Cloned plants can be grown in any country, in any season, so production is not limited by climate or growing season.

Whole plants can be created from genetically modified cells/tissues.

A plant variety produced by selective breeding or cloning that has distinct, uniform and desirable characteristics.

It prevents the risk of F₁ hybrids that occur when plants are crossed and grown from seeds, so the products are more uniform.

• It is an expensive process

• It is labour-intensive

• The process is susceptible to microbial contamination

With no genetic variation, all offspring are susceptible to the same diseases or environmental factors.

This risks large-scale loss of a country's or continent's crop, so growing a range of cultivars is recommended.

They must be screened for abnormalities that could lead to the new plants being infected.

An unexpected secondary metabolic reaction could cause stunted growth or even death in the new explants.

A small piece of tissue or cells taken from a parent plant and used to grow a new, genetically identical plant in tissue culture.

True

False — cloned plants have no genetic variation, so all offspring are susceptible to the same diseases.

Asexual reproduction is much less common in animals than in plants.

A form of asexual reproduction in which offspring develop from an unfertilised egg, producing natural clones (e.g. in aphids).

• Parthenogenesis (asexual reproduction, e.g. in aphids)

• The formation of identical twins

Identical twins that develop from a single zygote which splits at the embryo stage, giving offspring with the same genotype.

An egg is fertilised by a sperm, forming a zygote.

The single zygote undergoes a few cell cycles (mitotic divisions) to become an embryo.

At the embryo stage, the embryo splits in two.

The two identical embryos develop in utero together, producing identical offspring.

Because they both develop from a single zygote that splits at the embryo stage, rather than from two separate zygotes.

They have the same genotype, the same gender, and an identical phenotype.

Because they are formed from separate eggs and sperm, so they do not share the same genotype.

Mutations occur with every cell cycle.

This means that from the moment the embryo splits, Twin A gradually accumulates slightly different DNA base sequences to Twin B.

By birth, their genomes already differ slightly, and they become more dissimilar as they age.

Identical twins share the same genome only until the point at which the embryo splits into two.

Parthenogenesis is a form of asexual reproduction seen in some small animals such as aphids.

False — asexual reproduction is much less common in animals than in plants.

True

The offspring are clones of each other but not clones of their parents.

• An early embryo is deliberately divided into two half embryos (or into single identical cells)

• Each half embryo (or cell) is inserted into a surrogate mother

• The surrogate carries the embryo through gestation and gives birth to genetically identical twins

To boost yields of livestock and to promote desirable characteristics in the offspring.

Although it guarantees desirable characteristics, it is not possible to predict how many offspring will be produced.

A method of reproductive cloning in which the nucleus of a somatic (body) cell is transferred into an enucleated egg cell, which is then stimulated to develop into an embryo that is a clone of the nucleus donor.

Dolly the sheep, cloned in Edinburgh, UK, in 1996.

• The animal to be cloned, which donates a somatic cell

• The female that donates an egg cell

• The surrogate mother

• The animal to be cloned donates a somatic (body) cell, e.g. from the udder

• An egg cell is extracted from the egg donor and enucleated (its nucleus is removed by suction and discarded)

• The nucleus from the somatic cell is injected into the enucleated egg cell

• The hybrid cell is treated to encourage it to divide by mitosis

• The embryo is implanted into the surrogate mother for gestation and birth

In SCNT, the egg cell taken from the donor is enucleated, meaning its nucleus is removed and discarded before the somatic nucleus is injected.

A technique in which cloned cells are used to replace dead or damaged cells that cause a loss of function in an individual, rather than to produce a whole new organism.

• An embryo is cloned as in reproductive cloning, then removed and subdivided

• Each embryo cell is a totipotent stem cell that can be cultured and artificially differentiated into any specialised cell type

• This produces specialised cells with the same genome as the sufferer, which can replace their damaged cells

It could be used to replace specialised brain tissue in sufferers of Parkinson's Disease.

In therapeutic cloning, each individual embryo cell is a totipotent stem cell, able to be differentiated into any type of specialised cell.

There is currently a lot of potential for therapeutic cloning, but so far little clinical progress has been made.

False — the embryo is a clone of the somatic-cell (nucleus) donor, not the egg-cell donor.

Animals with desirable characteristics (e.g. high milk yield in cattle) can be cloned, ideal for maximising agricultural output.

It can remove less desirable characteristics from the gene pool over time, much as selective breeding has done.

It can help preserve endangered species, ahead of possible reintroduction of those species to the wild.

It can provide regenerated organs for the patient.

Because such organs are a direct genome match to the patient, there is no risk of rejection by the immune system.

The cloning process used to produce animal clones; it is very hit-and-miss, e.g. it took hundreds of unsuccessful attempts to clone Dolly the sheep.

The process is very hit-and-miss:

• It took hundreds of unsuccessful attempts to clone Dolly the sheep

• There are unknown long-term effects of the cloning process

• A high number of early deaths

• Genetic abnormalities

• Abnormally large growth (Large Organ Syndrome)

• Abnormalities in large organs (e.g. kidneys) or in the immune system

A condition in which some surviving cloned animals grow abnormally large, which can cause breathing and circulatory problems in adult animals.

Cloning appears to disrupt the normal regulation of gene expression. No precise 'cause and effect' has yet been ascribed to the cloning process.

Cloning destroys embryos which could, in theory, develop into a healthy adult animal.

Embryo cloning is well accepted and noncontroversial in the field of livestock farming.

Because of the many problems associated with it — the hit-and-miss nature of SCNT, high early death rates, genetic abnormalities, Large Organ Syndrome, and ethical objections to the destruction of embryos.

True

False — SCNT is very hit-and-miss, e.g. it took hundreds of attempts to clone Dolly the sheep.

The use (harnessing) of the processes carried out by living organisms to produce useful products or to carry out useful services.

• To produce useful products, such as foods and medicines

• To carry out useful services, such as sewage treatment, composting and bioremediation

• Sewage treatment

• Composting

• Bioremediation

Because they:

• Have simple growth requirements

• Use food that is cheap and readily available

• Occupy very little space

• Reproduce quickly and have short life cycles

• Do not have non-productive tissues and organs

• Can be grown on an industrial scale

Microorganisms reproduce quickly and have short life cycles, so large populations (and therefore large amounts of the useful product) can be generated rapidly.

Resources are not wasted maintaining structures that do not contribute to making the useful product, making the process more efficient and economically favourable.

Because microorganisms have simple growth requirements, occupy little space and reproduce quickly, there are many economic advantages to using them in biotechnology.

• Production of biofuels (to replace fossil fuels)

• Production of vaccines and antibodies to treat disease

• Production of hardy crop plants that can grow in arid conditions

• Counteracting threats from bioterrorism or bio-warfare

Through the production of biofuels, which can replace the use of fossil fuels.

The production of hardy crop plants that can grow in arid (dry) conditions.

True

False — microorganisms can be grown on an industrial scale to perform useful duties.

To make:\n\n- Human food\n\n- Animal feed

The human population is growing quickly, so there is a need for ever-more productive methods of food production.

Microorganisms have a rapid growth rate, meaning food can be produced very quickly compared with rearing animals or growing crops.

• Rapid growth rate (short generation time), so food is produced quickly\n\n- Production is not dependent on climate, weather or season\n\n- Microorganisms can be grown on waste materials as a cheap substrate

• The product is often high in protein and low in fat, making it a healthy food source\n\n- There are no animal welfare concerns, and it can be suitable for vegetarians

Conditions ideal for growing the desired microorganism also favour contaminating microorganisms.\n\nBecause microorganisms grow rapidly, any contamination spreads quickly and can spoil the product or produce toxins, so strict aseptic conditions must be maintained.

• The protein usually has to be isolated and purified from the growth medium\n\n- Some people may find food grown on waste unappealing, and the product may lack the taste or texture of traditional foods

It offers a fast, productive and scalable method of producing both human food and animal feed, helping to meet the demands of a rapidly growing population without relying on climate or large areas of farmland.

Microorganisms can be grown in fermenters in a relatively small space, independent of land quality or climate, and can use waste products as their substrate, so they require less land and fewer resources than rearing livestock or growing crops.

A large sterile vessel used to culture microorganisms on an industrial scale under carefully controlled conditions.

False — production is not dependent on climate, weather or season.

True

A set of procedures used when culturing microorganisms to ensure the microbes being investigated do not escape and are not contaminated by other unwanted, possibly pathogenic, microbes.

They ensure that:

• The microbes being investigated do not escape

• The culture does not become contaminated with another unwanted, and possibly pathogenic, microbe

Any four of:

• Washing hands thoroughly

• No food or drink allowed in the lab

• Disinfecting work surfaces with disinfectant or alcohol

• Wearing gloves and goggles

• Working close to a lit Bunsen burner

• Flaming equipment

• Sterilising (in an autoclave) or disposing of all used equipment

The flame creates an updraught of air, which prevents contamination of the culture by airborne microbes (such as fungal spores).

After taking a sample and before replacing the plug, the neck of the culture tube should be flamed to kill any microorganisms present.

• Pour sterile agar into the petri dish, cover with the lid and leave to cool

• Sterilise the inoculating loop in the Bunsen burner flame

• Remove the plug and flame the neck of the culture tube

• Take a sample from the culture tube using the inoculating loop

• Flame the neck of the culture tube again before replacing the plug

• Gently wipe the loop on the surface of the agar

• Sterilise the loop again, then tape the lid and incubate

A live bacterial cell that is able to divide and form a colony on an agar plate.

It is used to test the efficacy of different antibiotics (or antiseptics), and is commonly used to test for antibiotic resistance in bacteria. Its advantage is that multiple antibiotics can be tested at once.

• Pre-soak paper discs in the different antibiotic solutions

• Spread a sample of diluted bacterial broth over the surface of a sterile agar plate

• Lightly press the paper discs onto the agar, evenly distributed and not touching each other or the edges

• Incubate the plate overnight at an optimum temperature

• Examine the results with the petri dish lid on

So that the effects of the different antibiotics can be fairly compared, ensuring any difference in the clear zones is due to the antibiotic itself rather than differences in concentration.

The antibiotic diffuses outwards from the disc, forming a concentration gradient (most concentrated at the disc). Where the bacteria are susceptible to the antibiotic, no bacteria grow, producing a clear zone. The zone ends where the antibiotic concentration falls too low to affect the bacteria.

The most effective antibiotics need a lower concentration to kill bacteria, so they produce the largest clear zones.

If the bacteria are completely resistant to an antibiotic, there is no clear zone around that disc.

The lowest concentration of a substance (e.g. an antibiotic) that will inhibit the growth of a microorganism.

True

False — bacteria that are resistant produce no clear zone; the largest clear zone shows the most effective antibiotic.

The culturing of microorganisms under controlled conditions in a fermenter to produce a useful product.

• The microorganism itself, e.g. mycoprotein

• A product made by the microorganism, e.g. insulin

• Batch fermentation

• Continuous fermentation

A method in which microorganisms are grown in batches in the fermentation vessel; once the culture cycle is complete the product is removed, the fermenter is cleaned, and a new batch is grown.

Because the microorganisms are grown as a single, self-contained batch: nothing is added or removed during the culture cycle, and once complete the whole product is harvested before a new batch is started.

A method in which microorganisms are continually grown and the products harvested, with nutrients added and waste removed throughout the culturing process.

In continuous fermentation, nutrients are added and products/waste are removed continuously throughout the process while growth continues.

In batch fermentation, nothing is added or removed during the cycle; the product is only harvested at the end before the fermenter is cleaned and restarted.

In batch fermentation, once the culture cycle is complete the product is removed, the fermenter is cleaned, and a new batch of microorganisms is grown.

To keep conditions optimum so that the growth and productivity of the microorganisms are maximised, giving the greatest yield of the required product.

• pH

• Temperature

• Oxygen availability

• Nutrient supply

• Agitation (mixing)

• Contamination

• Waste removal

It keeps the microorganisms evenly distributed and ensures even access to nutrients, oxygen and temperature throughout the vessel, maintaining optimum conditions for growth.

Unwanted microorganisms would compete with the culture for nutrients and space and could reduce the yield or spoil the product, so the fermenter is kept sterile.

True — microorganisms are grown as a single self-contained batch, with nothing added or removed during the cycle.

False — that describes continuous fermentation; in batch fermentation nothing is added or removed during the cycle.

• Direct counting

• Viable counting

• Turbidity

A method of measuring a microorganism population that counts all individual cells in a sample, including both living and dead cells.

A method of measuring a microorganism population that involves culturing samples and counting the colonies that grow, so only living cells are taken into account.

A measure of the cloudiness of a suspension (how much light can pass through it), taken as an absorbance reading using a colorimeter. It reflects both living and dead microorganisms in solution.

As the microorganisms reproduce and the population grows, the suspension becomes progressively more turbid (cloudy).

Measuring how much light passes through the suspension at fixed time intervals after inoculation allows the changing turbidity, and therefore the population size, to be estimated.

• A turbidity meter

• A light sensor

• A colorimeter (connected to a datalogger)

1. Lag phase

1. Log (exponential) phase

1. Stationary phase

1. Decline (death) phase

The population size increases slowly as the microorganism population adjusts to its new environment and gradually starts to reproduce.

There is a high availability of nutrients and plenty of space, so the population moves into exponential growth, doubling at each division.

The population reaches its maximum because it is limited by resources, such as a lack of nutrients or a build-up of toxic substances.

During the decline phase, the death rate exceeds the reproduction rate, due to a lack of nutrients and a build-up of toxic substances.

The process of asexual reproduction in bacteria in which one cell divides into two identical daughter cells, each containing a single copy of the circular DNA molecule and a variable number of plasmids.

• The single, circular DNA molecule undergoes DNA replication

• Any plasmids present also replicate

• The parent cell divides into two cells, with the cytoplasm roughly halved between them

• Each daughter cell contains a single copy of the circular DNA molecule and a variable number of plasmids

N = N₀ × 2ⁿ

• N = the final number of bacteria

• N₀ = the initial number of bacteria

• n = the number of divisions

Bacterial numbers cover a very wide range of very small and very large values, which is difficult to display on a traditional linear scale.

A logarithmic scale allows this wide range of values to fit onto a single graph. Log scales can be identified by their uneven intervals between values on an axis.

The number of microorganisms dying equals the number being reproduced by binary fission, so the population size stays constant.

False — viable counting only counts living cells, as it relies on colonies growing from the cultured sample.

True

Factors such as:

• temperature

• pH

• nutrient availability

To avoid contamination of the plates by unwanted microorganisms, which would otherwise affect the reliability of the results.

A continuous layer of bacterial growth formed when colonies are too numerous to count or overlap, so individual colonies can no longer be distinguished.

A serial dilution method is used to dilute the bacteria in the broth before plating them onto the agar.

A series of dilutions of a stock solution in which the concentration decreases by the same quantity (e.g. the same factor) between each successive test tube.

To create a less dense culture of cells, which means more countable colonies when studying bacteria or yeast populations (rather than an uncountable lawn).

In a 'doubling dilution' serial dilution, the concentration is halved between each test tube.

A live bacterial cell that is able to reproduce and form a colony on the agar plate.

• Spread a sample of diluted bacterial broth onto the surface of each sterile agar plate

• Tape the lid shut

• Keep three plates in the fridge overnight (5°C) and three in the incubator overnight (25°C)

• Count the number of colonies the next morning, keeping the lid on

• Calculate the average number of colonies and compare results at each temperature

To prevent contamination of the culture and to avoid releasing potentially harmful microorganisms, maintaining safe aseptic conditions.

25°C is close to the optimum temperature for enzyme activity in the bacteria, so cellular reactions occur rapidly and growth is fast.

At 5°C the enzymes' cellular reactions are very slow, so growth is much slower, producing fewer and smaller colonies (or none at all).

The pH of the broth is altered by adding different buffer solutions of different pH levels.

Turbidity (cloudiness) of the culture can be used as a measure of growth instead of counting colonies.

Nutrient availability is altered by using agar plates with different nutrient contents.

True

False — bacteria grow faster at 25°C, which is closer to the optimum temperature for enzyme activity.

An enzyme that is attached to an insoluble material to prevent it mixing with the product.

• Attached to an inert substance

• Enclosed in a capsule

• Contained within a partially permeable membrane

So that the enzyme can be reused in future processes rather than being discarded after a single use.

It also avoids the need to separate the enzyme from the product during downstream processing.

• The immobilised enzymes are contained within a column, through which the substrate is filtered in solution

• As the substrate runs through the column, enzyme-substrate complexes form and products are produced

• The products flow out of the column, leaving the enzymes behind to catalyse the reaction again

In an immobilised enzyme column, the substrate is filtered through in solution, forming enzyme-substrate complexes.

• There is no enzyme in the product, so it is uncontaminated and needs no further processing or filtering

• The enzyme can be reused multiple times, which is efficient and cost-effective (enzymes are expensive)

• They have a greater tolerance of temperature and pH changes, as immobilisation makes them more stable

• Specialist, expensive equipment is required

• Immobilised enzymes are more costly to buy, so are unlikely to be worthwhile for smaller industries

• The rate of reaction is sometimes lower, as the enzymes cannot freely mix with the substrate

Because the enzyme is attached to an insoluble material and stays behind (e.g. in the column), so there is no enzyme in the product — it is uncontaminated.

Lactase.

Penicillin acylase.

Glucose isomerase.

Lactose is a disaccharide that is broken down by lactase into glucose and galactose.

The cost implications — there are various considerations regarding the economic value of immobilising enzymes (e.g. expensive equipment and enzymes versus the savings from reuse and no downstream separation).

It converts lactose into glucose and galactose.

It converts penicillin into a form that is effective against penicillin-resistant organisms, helping to overcome penicillin resistance.

Fructose is a sweeter sugar, so a lower quantity is needed to sweeten foods.

True

False — the enzyme stays attached to the insoluble material, so the product contains no enzyme.