7-Genetic Variation & Its Control

Question 0

What does the nucleus of a cell contain?

Answer 0

Chromosomes.

Question 1

Where is the information that results in plants and animals having similar characteristics carried?

Answer 1

By genes in the sex cells from which they develop.

Question 2

What are chromosomes made up of?

Answer 2

DNA.

Question 3

What is a gene?

Answer 3

A section of a chromosome.

Question 4

What genes do?

Answer 4

Carry information that control the characteristics of an organism.
Different genes control different characteristics.

Question 5

What do chromosomes come in?

Answer 5

Pairs, but different species have different numbers of pairs, e.g. Humans have 23.

Question 6

What is variation?

Answer 6

Differences between individuals of the same species.

Question 7

What might variation be due to?

Answer 7

Genetic causes (i.e. different genes that've been inherited).
Environmental causes (i.e. conditions in which the organism has developed).
It's usually a combination of both.

Question 8

Why might identical twins grow up to look slightly different?

Answer 8

Environment has altered the way they look. E.g. if one has a diet high in fat & does little exercise then he can become fatter than his brother.

Question 9

What is an example of genetic variation?

Answer 9

Different colours of dogs’ coats.

Question 10

What happens during sexual reproduction?

Answer 10

The sperm from the male fuses with an egg from the female. The genes are mixed to form a completely new individual.

Question 11

Why does sexual reproduction produce a lot of variation?

Answer 11

The mixing of genes is completely random.

Question 12

What is asexual reproduction?

Answer 12

One parent produces individuals that are genetically identical to the parent (clones).

Question 13

Does asexual reproduction cause variation?

Answer 13

No, the individuals have exactly the same genetic information.

Question 14

Can plants reproduce asexually?

Answer 14

Yes, many do so naturally and the offspring are clones of the parent.

Question 15

Why would a gardener choose to take cuttings?

Answer 15

When they have a plant with the desired characteristics, they may want more.
It’s a quick and cheap way of producing new plants.

Question 16

How should you take cuttings?

Answer 16

By taking stem, leaf or root cuttings.

These should be grown in a damp atmosphere until roots develop.

Question 17

What are clones?

Answer 17

Genetically identical individuals.

Question 18

How do you prepare a tissue culture?

Answer 18

1. Parent plant with desired characteristics selected.
2. A few cells scraped off into several beakers with nutrients and hormones.
3. Week or 2 later lots of genetically identical plantlets growing. The same can be done to these.
4. Whole process must be aseptic (carried out in absence of harmful bacteria) or new plants will rot.

Question 19

How are embryo transplants carried out?

Answer 19

1. Parents with desired characteristics mated.
2. Embryo removed before cells become specialised.
3. Embryo split into several clumps.
4. These embryos implanted into uteruses of sheep who’ll eventually give birth to sheep.

Question 20

What are the genetics of the offspring from embryo transplants?

Answer 20

Genetically identical to one another but not to the parents.

Question 21

Why do farmers use embryo transplants?

Answer 21

Don’t have to wait for normal breeding cycles.
Can produce many more offspring.
Can use only the best animals with desired characteristics.

Question 22

How is adult cell cloning/fusion cell cloning carried out?

Answer 22

• DNA from donor animal inserted into empty egg (nucleus removed).
• Electric shock causes egg to begin to divide to form embryo cells which contain the same genetic info as the donor.
• When embryo is ball of cells it’s implanted into the womb of an adult female.

Question 23

What are GM (genetically modified) crops?

Answer 23

Crops that have had their genes modified by the addition of new DNA.

Question 24

Why might crops be genetically modified?

Answer 24

• To improve crop yield, eg larger tomatoes etc.
• To improve resistance to pests or herbicides, eg soy plants have been made resistant to herbicides so farmers can eliminate weeds without killing the crop.
• To extend the shelf-life of fast ripening products, eg tomatoes.

Question 25

What are some concerns about GM crops?

Answer 25

• Genes from GM crops could be transferred via pollen to non-GM crops or to other plants. Eg resistance to herbicides to weeds creating ‘superweeds’.
• Nectar from GM crops can harm insects that feed on it.
• Uncertainty about the effects of eating GM crops on human health.

Question 26

Why are genes transferred to the cells if animals and microorganisms at an early stage?

Answer 26

So they develop the desired characteristics which can be passed on asexually or if the organism is cloned.

Question 27

Where is insulin normally produced?

Answer 27

In the pancreas.

Question 28

What does insulin do?

Answer 28

Helps to control blood glucose levels.

Question 29

Why do diabetics need to inject insulin?

Answer 29

They don’t produce enough themselves.

Question 30

How can large quantities of insulin be produced?

Answer 30

1. Scientists use enzymes to cut a chromosome at specific places so they can remove the piece of DNA they want. In this case insulin.
2. Another enzyme used to cut open a plasmid. Other enzymes are used to insert the human DNA into the plasmid.
3. Plasmid is inserted into the bacterium which divides rapidly. Soon there are millions if bacteria with instructions to make insulin.
4. Bacteria cultured on large scale and commercial quantities of insulin are produced.

Question 31

What is recombinant DNA cloning?

Answer 31

DNA fragment transferred from one organism to another. Could be used to produce bacteria that will make insulin or GM crops with desired characteristics.

Question 32

What is reproductive cloning?

Answer 32

Used to generate an animal that has the same nuclear DNA as another currently/previously existing animal (a twin). This can be used to produce farm animals with desired qualities.

Question 33

What are the pros of cloning plants, animals and humans?

Answer 33

Traditional breeding methods are slow.
Can predict characteristics of offspring.
Quick response to crop/livestock shortages.
Organ donation: clone has matching tissue so no risk of rejecting the organ.
Used to repopulate endangered species.

Question 34

What are the cons of cloning plants, animals and humans?

Answer 34

Loss of livelihood of traditional farmers.
Cloning companies may have monopoly on patent for clones.
Cloning is unnatural.
Fear of creating ‘perfect race’.
Human clones wouldn’t have ‘parents’.
Doesn’t allow natural evolution.

Question 35

What are the pros of GM crops?

Answer 35

More cost-effective.
Reduce pesticide use.
Can benefit human health.
Safe for human consumption.
Could provide more food for developing world.
Preserve habitats as less land needed for agriculture.

Question 36

What are the cons of GM crops?

Answer 36

Increase pesticide use as farmers spray freely.
Cross-contamination of GM crips could destroy non-GM trade.
Mainly benefit big GM companies.
Increasing yields won’t help developing world as distribution is the problem not the amount.
Could affect wildlife as there are no weeds as a food source.