Genetic Modification (Edexcel GCSE Combined Science: Biology): Flashcards
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- FrontSelective Breeding
Selective breeding (artificial selection)
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Selective breeding (artificial selection)
Selecting individuals with desirable characteristics and breeding them together.
Inbreeding
Breeding together only the 'best' animals or plants, which are closely related to each other.
Describe the steps of selective breeding.
Select individuals with the desired characteristics and breed them together
Select the offspring that show the desired characteristics and breed them together
Repeat this process over many successive generations
Why must selective breeding be repeated over many generations?
Because not all of the offspring will show the desired characteristics.
Only after many generations can you produce a new breed that reliably shows the selected characteristics in all offspring.
Give three characteristics that animals are commonly selectively bred for.
Cows, goats and sheep that produce lots of milk or meat
Chickens that lay large eggs
Dogs with a gentle nature, sheep with good quality wool, or horses with a very fast pace
From which wild animal are all breeds of domestic dog descended?
Wolves.
Give three characteristics that plants are commonly selectively bred for.
Disease resistance in food crops
Increased crop yield
Hardiness to weather conditions (e.g. drought tolerance), better tasting fruits, or large/unusual flowers
Which vegetables have been produced by selectively breeding wild brassica?
Cauliflower, cabbage, broccoli, brussel sprouts, kale and kohlrabi.
What problems can inbreeding cause?
A reduction in the gene pool — fewer alleles (different versions of genes) in the population
An increased chance of organisms inheriting harmful genetic defects
Greater vulnerability to new diseases, as resistant alleles are less likely to be present
Selective breeding must be repeated over many before a reliable new is produced.
generations / breed
Inbreeding reduces the pool, which is the number of (different versions of genes) in a population.
gene / alleles
Genetic engineering
Modifying the genome of an organism to introduce desirable characteristics, by removing or altering genes within the organism, or by inserting genes from another organism.
Recombinant DNA
The DNA of an organism that now contains DNA from another organism as well.
What is meant by a 'transgenic' or 'genetically modified' organism?
An organism that has received genetic material from another organism.
Why has the gene for human insulin been inserted into bacteria?
So the bacteria produce human insulin.
This insulin can then be collected and purified for medical use by diabetics.
How have crop plants been genetically modified to resist insect pests?
A gene from a bacterium that produces a poison which kills insects is inserted into the crop.
This makes the crop resistant to insect pests such as caterpillars.
How can crops be genetically modified to help with weed control?
They are made resistant to certain herbicides.
When the herbicide is sprayed on the crop it only kills the weeds and does not affect the crop plant.
What is 'golden rice' and why was it developed?
Rice genetically modified with genes from another plant and a bacterium so the grains produce a chemical that is turned into vitamin A in the human body.
It could help prevent vitamin A deficiency in certain areas of the world.
What is gene therapy?
Inserting working versions of genes into people with a genetic disease caused by faulty genes, to try to treat the inherited disorder.
An organism that receives DNA from another organism is described as , and its DNA is called DNA.
transgenic / recombinant
The gene for human has been inserted into so the protein can be collected and purified for diabetics.
insulin / bacteria
Restriction enzymes (Higher Tier Only)
Enzymes used to cut DNA at specific sequences to isolate the required gene, leaving 'sticky ends'.
Sticky ends (Higher Tier Only)
A short section of unpaired bases left when DNA is cut by a restriction enzyme.
Plasmid (Higher Tier Only)
A circle of DNA found inside bacterial cells.
What is the role of restriction enzymes in genetic engineering? (Higher Tier Only)
They isolate the required gene by cutting it out, leaving it with 'sticky ends' (unpaired bases).
The same restriction enzyme is used to cut the bacterial plasmid, leaving it with corresponding sticky ends.
What is the function of DNA ligase? (Higher Tier Only)
It joins the isolated gene and the plasmid together.
If two pieces of DNA have matching sticky ends, DNA ligase links them to form a single, unbroken molecule of DNA.
Why must the gene and the plasmid be cut with the same restriction enzyme? (Higher Tier Only)
So that they have matching (corresponding) sticky ends.
This allows DNA ligase to join them together into one DNA molecule.
Outline the process of genetic engineering. (Higher Tier Only)
The required gene is located in the original organism and isolated using restriction enzymes, leaving sticky ends
A bacterial plasmid is cut with the same restriction enzyme to leave corresponding sticky ends
DNA ligase joins the gene and the plasmid together
The genetically engineered plasmid is inserted into a bacterial cell
When the bacteria reproduce, the plasmid is copied and the bacteria express the gene to make the protein
Why are genetically engineered bacteria placed in a fermenter? (Higher Tier Only)
So they can reproduce quickly in controlled conditions.
This allows large quantities of the human protein to be made.
enzymes cut DNA to isolate a gene, while joins the gene and plasmid together. (Higher Tier Only)
Restriction / DNA ligase
A is a circle of DNA found in bacterial cells, and DNA cut by a restriction enzyme is left with ends. (Higher Tier Only)
plasmid / sticky
Gene therapy
Inserting working versions of genes into people with a genetic disorder caused by faulty genes, to try to treat the disorder.
In which two fields are genetic engineering and selective breeding used?
Both are used in modern-day agriculture.
Genetic engineering is also used in modern-day medicine.
Besides their benefits, what must be considered when evaluating the use of genetic engineering and selective breeding?
Their use comes with certain risks.
There are also other practical and ethical implications to consider.
Give a medical benefit of genetic engineering.
Bacteria can be genetically modified to produce human insulin for diabetics.
Gene therapy may also be used to treat inherited disorders caused by faulty genes.
Give an agricultural benefit of genetically modifying crops.
Crops can be made resistant to insect pests or to herbicides.
They can also be modified to produce additional vitamins, such as vitamin A in golden rice.
How can golden rice benefit human health?
Its grains produce a chemical that is turned into vitamin A in the body.
This could help prevent vitamin A deficiency in certain areas of the world.
Give a disadvantage of selective breeding linked to genetic variety.
It can lead to inbreeding, which reduces the gene pool (fewer alleles in the population).
This increases the chance of harmful genetic defects and vulnerability to new diseases.
Genetic engineering and selective breeding are used in modern agriculture and , and their use raises practical and implications.
medicine / ethical
Genome
The entire set of genetic material of an organism.
Faulty allele
A faulty version of a gene that can cause an inherited disorder, such as cystic fibrosis.
What was the Human Genome Project, and when was it completed?
An international, collaborative research effort to determine the DNA sequence of the entire human genome and record every human gene.
It was completed in 2003.
Give three reasons why the Human Genome Project was an important breakthrough.
The prediction and prevention of diseases
The testing and treatment for inherited disorders
The development of new and improved medicines
How can the Human Genome Project help with the prediction and prevention of diseases?
Knowing which genes predispose people to diseases (such as cancers and heart disease) lets doctors give more specific advice on the best lifestyle and diet to avoid or delay them.
Doctors can also better predict which diseases someone might develop and ensure early treatment.
How does the Human Genome Project help with inherited disorders?
Faulty alleles (such as those causing cystic fibrosis) can be identified much more quickly than in the past.
People can then be tested for them, and treatments for the disorder can be developed.
How has the Human Genome Project led to new and improved medicines?
New drugs can be designed and tailored to people's genetic variations, made more effective and with fewer side-effects.
Doctors can also better predict how well an existing drug will work for a specific person.
Give potential drawbacks of the Human Genome Project.
People told they have a high chance of a disease may suffer increased anxiety and stress, possibly unnecessarily
People with genetic disorders or faulty alleles could be pressured into not having children
They could be unfairly discriminated against by employers or insurers
The Human Genome Project was completed in the year and recorded every found in humans.
2003 / gene
People known to carry a faulty allele could be unfairly discriminated against by employers or , who could make life much more expensive.
insurers / insurance
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