Variation, genetic modification, and cloning

diploid number of chromosomes

46

haploid number of chromosomes

23

variation within a species can be...

- Genetic (eye colour, hair type)

- Environmental (learned behaviour, hair length)

- or a combination of both

mutation

a rare, random change in genetic material that can be inherited.

evolution

a change in the inherited characteristics of a population over time through a process of natural selection.

this may result in the formation of a new species.

how does evolution occur?

evolution occurs through natural selection of variants that give rise to phenotypes best suited to their environment.

where are two new species formed?

if two population of one species become so genetically different in phenotype that they can no longer interbreed to produce fertile offspring.

they have produced two new species.

Genome

Genetic information in an organism's chromosomes, carried in DNA.

Genetic modification

changing the DNA molecule.

Name the 3 types of genetic manipulation

1. moving a gene between species to create transgenic species with new traits.

2. changing the base sequence of a gene to alter protein structure.

3. deleting a gene from a chromosome.

transgenic organisms

created by transferring DNA/genetic material between species, a process not occurring naturally.

transgenic organisms contain all of its own DNA + some DNA of another organism in every cell.

why are enzymes used?

to cut and paste DNA

Restriction enzymes

- collected from bacteria

- recognize specific DNA sequences (restriction sites.)

- cut DNA at these sites, creating sticky ends.

sticky ends

overhanging single stranded DNA ends that can pair with matching sticky ends from other DNA pieces.

recombinant DNA

- makes temporary seal.

- created by joining DNA pieces with matching sticky ends.

- forms a hybrid DNA molecule with a temporary join.

DNA ligase

- makes permanent seal.

- another enzyme from bacteria.

- makes the temporary join permanent by creating strong bonds.

vector

a vector is something used to transfer DNA

plasmids

small circles of DNA in bacteria, carrying a few genes, including antibiotic genes.

plasmids: natural exchange

plasmids are naturally swapped between bacteria.

plasmids: scientific use

scientists use plasmids to introduce foreign genes into bacteria.

plasmids: extraction and cutting

plasmids are extracted from bacteria and cut open with restriction enzymes.

recombinant plasmids:

foreign DNA cut with the same restriction enzymes is mixed with plasmids to create recombinant plasmids.

plasmids: permanent joins

DNA ligase enzyme makes the temporary joins in recombinant plasmids permanent.

plasmids: mixing with bacteria

recombinant plasmids are mixed with bacteria that lack plasmids.

uptake of plasmids

some bacteria take up the recombinant plasmids.

plasmids: transgenic bacteria

bacteria that take up the plasmids become transgenic.

plasmids: new properties

these genetically modified bacteria gain new properties.

plasmids: examples

transgenic bacteria can be used to produce medical drugs (like insulin.)

bacteriophage vectors

viruses that target bacteria

bacteriophage vectors: infection process

- bacteriophage DNA injected into the bacterial chromosome, reprogramming the cell to produce new pacteriophage particles.

recombinant bacteriophage DNA

scientists delete harmful genes and replace them with foreign genes, to create recombinant bacteriophage DNA.

transgenic bacteria creation

recombinant bacteriophages infect bacteria, injecting recombinant DNA into the bacterial cytoplasm.

bacteriophages: useful reprogramming

the foreign gene reprograms the bacterial cell to perform useful functions, such as producing medicine.

applications of GM bacteria: stability and culturing

transgenic bacteria are stable and can be cultured in large scale in fermenters.

application of GM bacteria: product separation

useful products from these bacteria can be separated from the bacterial cells in the fermenter.

application of GM bacteria: purification

the separated proteins (products) are purified for use.

products of GM bacteria grown in fermenters (3)

1. enzymes

2. medicines

3. hormones (insulin)

how does antibiotic resistance arise?

due to random mutations, populations of bacteria show variation. (including in their resistance to antibiotics.)

describe the process of antibiotic resistance

1. treating bacteria with antibiotics will kill many of them. However, the bacteria with the most resistance are likely to survive.

2. this variation/ the genes that code for increased resistance are passed on to the next generation. As the genes are copied, random mutations occur, some of which will increase the level of resistance.

3. this process is repeated until the bacteria become completely resistant to antibiotics.

4. therefore, excessive use of antibiotic creates a selection pressure to make future generations of bacteria more resistant.

definition of natural selection

the process where organisms better adapted to their environment survive and reproduce.

driving force of natural selection

environmental factors (eg. climate and predators)

natural selection: selection pressure

natural environmental challenges

natural selection: outcome

traits that enhance survival and reproduction.

examples of natural selection

development of camouflage in animals.

time scale of natural selection

takes many generations

definition of artificial selection

the process where humans select specific traits to breed in organisms.

driving force of artificial selection

human choices

selection pressure of artificial selection

human-imposed criteria

outcomes of artificial selection

traits that are desirable to humans become more common.

time scale of artificial selection

occurs over a few generations.

describe the process of selective breeding (artificial selection)

- parents with the desired characteristics (from a mixed population) are chosen.

- they are bred together.

- the offspring with these desired characteristics are then bred together.

- this continues over many generations until all of the offspring show the desired characteristic.

disadvantages of selective breeding

- leads to inbreeding, which results in some species being more prone to disease or inherited defects.

- this is because it is more likely that harmful homozygous recessive combinations will occur in a small breeding population.

- alleles are lost, and there is a lack of genetic variation amongst the population. (causes problem is a new disease arises.)

reasons for genetic modification in plants

1. increases resistance to infectious diseases (fungi and bacteria)

2. improves resistance of plants (to herbivore insects)

3. provides immunity to chemical herbisides.

bioremediation

GM plants are being developed to clean up soil that has been contaminated with pollutants.

describe the process in creating transgenic plants

1. plasmids from bacteria are extracted, and replace disease-causing genes with useful foreign genes. This creates recombinant plasmids.

2. recombinant plasmids are mixed with plant cells.

3. some plant cells take up the recombinant plasmids. These integrate into plant chromosomes and make them transgenic.

4. the transgenic plants are cloned by tissue culture to produce whole plants.

definition of micropropagation (cloning plants)

used to produce large quantities of GM plants that all carry the foreign gene with useful properties.

describe the stages of tissue culture (micropropagation)

1. explant removal - taken from the selected parent plant.

2. sterilization - surface sterilized with disinfectant, then rinsed with sterile water to reduce contamination.

3. placement in vessel - sterilized explant placed in a sterile tissue culture vessel with a sterile growth medium.

4. growth medium - contains nutrients that encourage cell growth and division, forming a callus.

5. callus development - transferred to a fresh growth medium with plant growth regulators to develop roots, stems, and leaves.

commercial potential of micropropagation

micropropagation produces vast numbers of plants from a selected parent plant.

micropropagation explant size

original explant may consist of only a few cells.

micropropagation yield

high yield - a single plant could yield hundreds/thousands of explants.

micropropagation: explant multiplication

more explants can be generated from previously taken explants.

micropropagation: advantages over cuttings

tissue culture offers higher yield compared to taking cuttings.

micropropagation: disease-free plants

resulting plants can be free of disease if the original explants are from a disease free part of the parent plant.

name the two cloning techniques

1. embryo splitting.

2. cloning from an adult body cell.

describe the process of embryo splitting

1. growing embryo taken from animal womb.

2. embryo split into two or more cells.

3. each cell grows into embryo.

4. embryos implanted into different surrogate mothers.

5. results in cloned offspring (which are different from the surrogate mothers.)

* uses embryonic stem cell's natural ability to divide and grow into complete embryos.

describe the process of cloning from an adult body cell

1. nucleus removal - a nucleus with its diploid set of chromosomes is removed from an adult body cell.

2. insertion into egg cell - the nucleus is inserted into an enucleated egg cell (an egg cell where the original haploid nucleus has been removed.)

3. embryo growth - the egg cell is allowed to grow into an embryo on an artificial medium.

4. implantation - embryo implanted into surrogate mother.

5. birth of offspring - the offspring inherits all genetic material from the animal that provided the adult diploid cell nucleus (ie. not the surrogate.)

definition of pharming

cloning transgenic animals to create herds or flocks producing the same medicine.

name 3 examples of medicines produced by pharming.

1. Blood clotting Factor IX - treats hemophilia.

2. Alpha-1-Antitrypsin - treats cystic fibrosis.

3. Antibodies - targets cancer cells.

name the type of organism that makes antibiotics

bacteria

name the type of pathogen that is killed by antibiotics

bacteria

name 3 ways pathogens differ from viruses

1. viruses not recognised by the immune system.

2. viruses can be used as vectors.

3. always fatal

4. have a protein coat

name 2 ways viruses differ from other organisms

1. do not respire

2. cannot reproduce without a host

Plants can be genetically modified (GM) to make them resistant to pests.

Describe an investigation that could be carried out to find out if GM plants produce a better yield than normal plants.

• GM field and normal field

• same species / size / mass / length

• many plants / several fields

• mass / length / surface area of leaves / count fruit / count flowers

• stated time period

• same temp. / light intensity / carbon dioxide / water / mineral ions / soil / exposure to pests