B1.7 Genetic Variation

Question 1

What does the information genes carry result in?

Answer 1

It results in plants and animals having similar characteristics to their parents

Question 2

How are genes passed on?

Answer 2

In sex cells (gametes) from which the offspring develops

Question 3

What is asexual reproduction used for?

Answer 3

Producing individuals that are genetically identical to their parents

Question 4

How do genes operate?

Answer 4

They operate at a molecular level to develop characteristics that can be seen

Question 5

Where are chromosomes found?

Answer 5

In the nucleus

Question 6

What are most characteristics determined by?

Answer 6

Genetic and environmental factors

Question 7

What is genetic variation caused by?

Answer 7

The combining of genes from two parents

Question 8

What is environmental variation?

Answer 8

Any difference that has been caused by the conditions something lives in

Question 9

Describe sexual reproduction.

Answer 9

The fusion of male and female gametes, resulting in mixing of the genetic information from two parents and variation in the offspring

Question 10

Describe asexual reproduction

Answer 10

The production of genetically identical clones from a single parent as there is no mixing of genetic information so no variation in offspring.

Question 11

What are the advantages of sexual reproduction compared to asexual reproduction?

Answer 11

• Variation
• The offspring inherits stronger genes
• If an environmental change (e.g new disease) comes, not all will be wiped out

Question 12

What are the disadvantages of sexual reproduction compared to asexual reproduction?

Answer 12

• More risk
• Animals have to make effort to reproduce
• Some reproduction is dangerous

Question 13

What are chromosomes made up of?

Answer 13

Genes

Question 14

What are genes made up of?

Answer 14

DNA

Question 15

What are the two ways plants can be cloned?

Answer 15

• Cuttings

- Tissue culture

Question 16

Describe the process of cloning from cuttings

Answer 16

1) Remove a small piece of plant
2) Grow in the right conditions
3) Roots and shoots will form to give you a small complete new plant

Question 17

What conditions do plants from cuttings need to be grown in and why?

Answer 17

• Large leaves are removed : reduces water loss
• Rooting powder is used : contains root growing hormone (auxin) and fungicide to keep back fungus root
• Soil is kept warm : to keep shoot humid to reduce water loss
• Leaves are kept cool : stops fungus disease spreading in leaves and water loss
• Compost has a high proportion of sand in it : creates air spaces so new growing roots have oxygen for respiration

Question 18

What are the advantages to cutting cloning?

Answer 18

• Cheap
• Asexual
• Fast

Question 19

Describe the process of cloning using tissue culture

Answer 19

1) A small piece of tissue taken
2) Placed in substance to help it grow (e.g on a agar plate with nutrients and hormones e.g auxin to stimulate growth of roots and stems)
3) After about 12 weeks roots and stems start to appear
4) The new organisms are planted

Question 20

What are advantages of cloning with tissue culture?

Answer 20

• Fast
• Very space
• Can be grown all year

Question 21

Describe the process of cloning with embryo transplants

Answer 21

• Sperm cells and egg cells are added to each other
• Artificial fertilisation occurs
• The fertilised egg develops an embryo
• The cells of the embryo are split apart before they specialise
• Each cell develops into an individual embryo
• The surrogate mother is giving hormones to ensure readiness for pregnancy
• The embryo is implanted into her womb

Question 22

Describe the process of adult cell cloning.

Answer 22

• Egg cell removed from female’s ovary
• Nucleus removed from the egg cell
• Nucleus from male adult body cell removed and inserted into empty egg cell
• Egg cell stimulated by an electric shock, making it divide to form body cells
• Before the dividing cells specialise they are implanted into the surrogate mother to grow into a clone of the male body cell

Question 23

What are the advantages of cloning?

Answer 23

• Study of animal clones could lead to greater understanding of embryo development and aging (e.g age related disorders)
• Could help endangered species
• Produces “ideal” offspring for farming

Question 24

What are the disadvantages of cloning?

Answer 24

• Clones may not be as healthy as normal e.g Dolly the sheep had arthritis early
• Reduced gene pool, higher risk of a species being wiped out
• Ethical/moral problems

Question 25

Describe the process of genetical engineering.

Answer 25

• The useful gene needed is cut out of an organism’s chromosome (or a bacteria’s plasmid) using an enzyme
• Enzymes are used to split open another organism’s chromosome/plasmid and insert the useful gene

Question 26

What are four uses of genetic engineering?

Answer 26

• GM crops : crops with genes modified to make them resistant to herbicides, insects and viruses
• Sheep genetically engineered to produce substances e.g drugs in their milk to treat human diseases
• Gene therapy: genetic disorder sufferers e.g cystic fibrosis can have working genes inserted
• Bacteria can be genetically engineered to mass produce insulin

Question 27

What are the advantages to GM crops?

Answer 27

• Increases crop yield, so more food
• People in developing countries lack certain nutrients - crops can be engineered to produce contain them
• GM crops are already being grown with no problems

Question 28

What are the disadvantages to GM crops?

Answer 28

• Reduced farmland biodiversity : reduced numbers of weeds and flowers and therefore insects
• Possible risk to humans eating them (we don’t know long term effects)
• Transplanted genes can get out into the natural environment e.g weeds picking up herbicide resistant gene

Question 29

How are organisms ensured to develop with desired characteristics?

Answer 29

Desired genes can be transferred to them at an early stage of their development