Feeding the Human Race (OCR GCSE Combined Science A (Gateway): Biology): Flashcards
Exam code: J250
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Define selective breeding.
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Define selective breeding.
Choosing individuals with desirable characteristics and breeding them together, over many generations.
Describe the process of selective breeding.
Select parents with the desired characteristic and breed them.
Select the offspring that show it and breed those, repeating for many generations.
Why must selective breeding be repeated over many generations?
Only some offspring show the desired characteristic. Repeating it makes the characteristic appear reliably in all offspring.
Why is selective breeding also called artificial selection?
Humans choose which individuals breed, rather than the environment doing the selecting.
Give three characteristics livestock are selectively bred for.
High milk or meat yield in cattle, goats and sheep.
Large eggs in chickens.
Good quality wool in sheep.
Give three characteristics food plants are selectively bred for.
Disease resistance, increased crop yield and hardiness to weather such as drought.
Give an example of selective breeding in food plants.
Wild brassica, which has been bred into cabbage, cauliflower, broccoli, Brussels sprouts and kale.
Give an example of selective breeding in animals.
The domestic dog — every breed descends from wolves.
Define inbreeding.
Breeding together individuals that are closely related, which happens when only the 'best' stock is used.
Why is inbreeding a problem in selective breeding?
It reduces the gene pool, so there are fewer different alleles in the population.
Give two consequences of a reduced gene pool.
A greater chance of inheriting harmful genetic defects.
Greater vulnerability to new diseases, as resistant alleles are less likely to be present.
Give the main similarity between natural and artificial selection.
Both control which individuals get to reproduce, so both change the characteristics of a population over generations.
Give the main difference between natural and artificial selection.
In natural selection the environment decides which individuals survive to breed.
In artificial selection humans decide.
Breeding closely related individuals together is known as ＿＿＿＿＿＿＿＿.
Breeding closely related individuals together is known as inbreeding.
Selective breeding is also known as ＿＿＿＿＿＿＿＿ selection.
Selective breeding is also known as artificial selection.
True or False?
One round of breeding is enough to create a new breed.
False.
The process must be repeated for many successive generations.
True or False?
Selective breeding introduces genes from another species.
False.
It only selects from alleles already present in the species. Adding genes from another species is genetic engineering.
Define genetic engineering.
A process which involves modifying the genome of an organism to introduce desirable characteristics.
What does genetic engineering involve doing to an organism?
Removing, altering or inserting genes, often taking a gene from a different species.
Define genetically modified organism.
An organism whose genome has been changed by genetic engineering, so it carries DNA it would not have naturally.
How is genetic engineering used to produce insulin?
The human insulin gene is inserted into bacteria, which then make human insulin that can be collected and purified.
How can crops be genetically modified to resist insect pests?
A gene from a bacterium is inserted that makes the plant produce a poison which kills the insects.
Why are some crops modified to resist herbicides?
The herbicide can then be sprayed on the field and will kill only the weeds, leaving the crop unharmed.
What is golden rice and why was it developed?
Rice genetically modified to produce a chemical the body turns into vitamin A, to help prevent vitamin A deficiency.
Give two benefits of genetically engineering food crops.
Improved crop yields.
More nutritious crops, which can help fight deficiency diseases.
Why might a herbicide-resistance gene spreading be a problem?
If it passes to wild plants, it could create weeds that the herbicide no longer kills.
Give two other risks or concerns about genetic engineering.
The long-term effects on human health are not fully known.
There are ethical and religious objections to altering nature.
How might GM crops affect biodiversity?
They can have knock-on effects on wildlife in and around the fields, reducing the biodiversity of agricultural land.
An organism carrying DNA from another species is described as ＿＿＿＿＿＿＿＿ modified.
An organism carrying DNA from another species is described as genetically modified.
DNA that contains genetic material from two different organisms is called ＿＿＿＿＿＿＿＿ DNA.
DNA that contains genetic material from two different organisms is called recombinant DNA.
True or False?
Genetic engineering can move a gene between different species.
True.
That is what distinguishes it from selective breeding, which uses only alleles already in the species.
True or False?
A GM organism develops its new characteristic naturally.
False.
The characteristic is introduced artificially and would not have arisen on its own.
What is the first step of genetic engineering? (Higher Tier Only)
Locating the required gene in the original organism.
What is the role of restriction enzymes? (Higher Tier Only)
They cut the DNA at specific sequences to isolate the required gene.
Define sticky ends. (Higher Tier Only)
The short sections of unpaired bases left when a restriction enzyme cuts DNA.
Why is the plasmid cut with the same restriction enzyme? (Higher Tier Only)
So it is left with matching sticky ends that pair with those on the isolated gene.
Define vector. (Higher Tier Only)
Something used to carry the new DNA into a host cell — usually a bacterial plasmid.
What is the role of DNA ligase? (Higher Tier Only)
It joins the isolated gene and the cut plasmid together, forming one unbroken molecule of DNA.
What happens to the plasmid after the gene is inserted? (Higher Tier Only)
It is inserted into a host bacterial cell.
Why are host bacteria used in genetic engineering? (Higher Tier Only)
When they reproduce, the plasmid is copied too, so the gene spreads quickly and all the bacteria express it.
What is an antibiotic resistance marker used for? (Higher Tier Only)
It is inserted alongside the desired gene, so scientists can identify which cells have taken the new gene up.
List the main steps of genetic engineering in order. (Higher Tier Only)
Isolate the gene with a restriction enzyme, leaving sticky ends.
Cut a plasmid with the same enzyme and join them with ligase.
Insert the plasmid into host bacteria, which multiply and express the gene.
Why must the same restriction enzyme be used twice? (Higher Tier Only)
Different enzymes cut at different sequences, so the sticky ends would not match and ligase could not join them.
＿＿＿＿＿＿＿＿ enzymes cut DNA at specific sequences to isolate a gene. (Higher Tier Only)
Restriction enzymes cut DNA at specific sequences to isolate a gene.
The enzyme ＿＿＿＿＿＿＿＿ joins the gene and the plasmid together. (Higher Tier Only)
The enzyme ligase joins the gene and the plasmid together.
True or False?
A plasmid acts as a vector in genetic engineering. (Higher Tier Only)
True.
It carries the new gene into the host bacterial cell.
True or False?
Restriction enzymes join two pieces of DNA together. (Higher Tier Only)
False.
Restriction enzymes cut DNA. It is ligase that joins it.
Why must agricultural productivity rise?
The human population is growing while the amount of available land is falling, so more food must be produced from less land.
How is gene technology proposed as a solution to food security?
By genetically modifying crops and livestock to raise yields and make food production more intensive.
Give two practical benefits of GM crops in agriculture.
Higher yields from the same area of land.
Crops that resist pests, disease or drought, so less of the harvest is lost.
How can GM crops improve human nutrition?
They can be modified to contain extra vitamins or nutrients, helping to prevent deficiency diseases.
Roughly how much of the world's arable land grows GM crops?
Just over 10%, a figure that has grown rapidly since the 1990s.
What does the low share of GM farmland suggest?
There are still real problems and objections holding back a fully GM food supply.
Give one practical risk of using GM crops in agriculture.
Modified genes could spread to wild plants, for example creating weeds that herbicides no longer kill.
Give one ethical concern about GM in agriculture.
Objections to altering nature, including religious concerns and worries about the welfare of modified animals.
Why is uncertainty itself an argument against GM?
The long-term effects on human health and ecosystems are not yet known, so unforeseen problems may emerge.
How might intensive GM farming affect biodiversity?
It can have knock-on effects on wildlife in and around farmland, reducing the number of species there.
Why should an answer on GM give both sides of the argument?
The question asks you to weigh benefits against risks, so a balanced, reasoned case is needed.
Producing enough food for a growing population is known as the problem of food ＿＿＿＿＿＿＿＿.
Producing enough food for a growing population is known as the problem of food security.
Gene technology in farming raises both practical and ＿＿＿＿＿＿＿＿ considerations.
Gene technology in farming raises both practical and ethical considerations.
True or False?
Most of the world's farmland now grows GM crops.
False.
Only just over 10% of arable land is under GM crops.
True or False?
GM crops can raise food production without using more land.
True.
That is the main argument for them — higher yields from the same area.
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