selective breeding, cloning and genetic engineering (paper 2)

Question 1

define selective breeding

Answer 1

process by which humans breed plants + animals for particular genetic characteristics.
this ensures the genes for the chosen specific characteristics remain in the population

Question 2

4 examples in which a characteristic can be chosen for

Answer 2

• disease resistance in food crops
• animals that produce more meat or milk
• domestic dogs with gentle temperament
• large or unusual flowers

Question 3

3 main issues with selective breeding

Answer 3

• reduction in gene pool
• inbreeding can result in health problems
• new diseases and defects can occur

Question 4

how can new diseases and defects occur from selective breeding?

Answer 4

because selective breeding reduces genetic variation in a population which can make certain disadvantageous alleles more common

Question 5

how can interbreeding in health problems occur from selective breeding?

Answer 5

due to inbreeding there’s an increased chance that an allele that causes a harmful genetic defect is passed on to all the offspring

Question 6

how can selective breeding lead to a reduction in the gene pool? (4)

Answer 6

• number of different alleles in the population decreases
• because the alleles which dont code for the chosen characteristics are selected out
• alleles for the weaker non-desirable characteristics can be lost after many generations
• all offspring produced by selective breeding are closely related to each other (inbred)

Question 7

define genetic engineering

Answer 7

process which involves modifying the genome of an organism by introducing a gene from another organism to give it a desired characteristic

Question 8

why would plants crops be genetically engineered?

Answer 8

to be resistant to diseases or to produce bigger better fruits

Question 9

why would bacteria cells be genetically engineered?

Answer 9

to produce useful substances e.g. human insulin to treat diabetes

Question 10

what are GM crops?

Answer 10

where through genetic engineering genes from the chromosomes of humans and other organisms can be cut out and transferred to dells of other organisms

Question 11

what do GM crops generally show?

Answer 11

increased yields

Question 12

2 examples of GM crops

Answer 12

resistant to insect attack
resistant to herbicides

Question 13

describe the process of genetic engineering (5)

Answer 13

• enzymes used to isolate required gene
• isolated gene is inserted into a vector (plasmid or viral usually)
• vector used to insert gene into required cells
• genes are transferred to cells of animals, plants or microorganisms at an early stage in their development
• this way all cells get a copy of the gene and organism will develop with desired characteristic(s)

Question 14

what are the enzymes called that isolate a required gene

Answer 14

restriction enzymes

Question 15

how can you treat diabetes through genetic engineering? (3)

Answer 15

• bacteria genetically engineered to produce human insulin
• this has led to greater availability of insulin for diabetics and reduced cost of treatment
• effects of human insulin are identical and medication has very few side effects

Question 16

list the 4 examples of genetic engineering

Answer 16

treating diabetes
GM crops
Gm sheep
gene therapy

Question 17

why are sheep GM?

Answer 17

to produce specific substances in their milk

Question 18

benefits of plant cloning (4)

Answer 18

• produces lots of identical plants quickly at low costs
• many plants grow quickly for selling (good for economy)
• all the plants have the same beneficial characteristics
• used to preserve endangered species of plants

Question 19

explain the process of cuttings (4)

Answer 19

• shoot is cut from part of parent stock plant which has desirable characteristics
• cut end of shoot is treated with plant hormones to encourage roots to develop + grow
• cutting is planted in moist compost + rooting powder
• must be kept very well-watered to avoid it dying until its grown enough roots to survive normally

Question 20

define clones

Answer 20

genetically identical copies of an organisms that are formed through asexual reproduction

Question 21

advantages of embryo transplants (4)

Answer 21

• genetically identical offspring are produced i.e. clones therefore offspring have desired characteristics
• many offspring can be produced from one embryo
• process can be repeated frequently
• can transport high quality embryos around the world

Question 22

disadvantages of embryo transplants (5)

Answer 22

• reduced gene pool
• less variation
• all offspring are at equal risk if the conditions change
• all offspring same gender
• skilled and expensive work

Question 23

process of embryo transplants (9)

Answer 23

• sperm from best male individual is obtained
• Ova from best female individual is obtained
• artificial fertilisation occurs to produce a zygote
• zygote develops in an embryo
• embryo is split into clumps of cells many times before cells differentiate
• cloned embryos are implanted into uterus of host mother(s)
• host mothers are called surrogates
• cloned embryos develop into new individuals
• they are genetically identical to each other

Question 24

define tissue culture in plants

Answer 24

modern laboratory technique which uses small groups of cells from part of a plant to grow identical new cells

Question 25

2 ways tissue culture in plants is important

Answer 25

• preserving rare plant species
• used commercially in nurseries as it allows very large numbers of clones to be produced in as relatively small space

Question 26

benefits of tissue culture (4)

Answer 26

• clones retain desired characteristics
• expect high strike rate success
• plants are disease free and uniform
• production isn’t interrupted by seasons

Question 27

describe the process of adult cell cloning (5)

Answer 27

• nucleus removed from an unfertilised egg
• nucleus from adult body cell e.g. skin cell is inserted into the egg cell
• electric shock stimulates egg cell to divide by mitosis to form an embryo
• embryo cells contain same genetic information as adult skin cell
• when embryo has developed into a ball of cells its inserted into womb of and adult female to continue its development