sex genes and agriculture

Question 1

2nd agricultural revolution

Answer 1

1. inventions
2. breeding
3. crop rotation

Question 2

3rd agricultural revolution

Answer 2

1. high-yielding varieties
2. fertilisers
3. pesticides

Question 3

what is a hectare in metre squared

Answer 3

10,000 m2

Question 4

why is there a higher yield per area?

Answer 4

1. varieties x management
2. agriculture is mecanised
3. extensive use of inputs
4. use of new varieties is responsible for 50% of increase in yield

Question 5

pressures on agricultural systems

Answer 5

1. increased consumption of animal products puts pressure on agricultural systems.
2. feed conversion ratios are not good
3. feeding animals our crops is not inefficient use for it

Question 6

what do humans need to eat in their diet?

Answer 6

• carbs
• fats
• proteins
• fibre

Question 7

what is the most traded crop?

Answer 7

1. maize
2. rice
3. wheat
4. potato
5. cassava

Question 8

breeding

Answer 8

creating varieties (cultivars) with new combinations of genes. requires sexual reproduction.

Question 9

propagation

Answer 9

creating genetically uniform seeds or plants for growing commercially. can involve sexual production or vegetative propagation.

Question 10

how do annual plants grow?

Answer 10

from seeds produced sexually, harvested within 12 months. includes all main grain crops.

Question 11

how do perennial plants grow?

Answer 11

grown for longer than a year and harvested many times. often propagated vegetatively.

Question 12

how do tubers grow?

Answer 12

botanically perennials (as not grown from a seed) but are planted every year (vegetative propagation)

Question 13

what is an example of vegetative propagation?

one advantage of this

Answer 13

marram grass on sand dunes.

• offspring are genetically identical to parent plants and each other.

ADVANTAGE - no risks that come with sex.

Question 14

grafting

Answer 14

combining two different plants by inserting upper part of one plant to the root stock of another.

Question 15

advantages and disadvantages of clonal propagation

Answer 15

+ offspring are genetically identical to each other and to their parents, and are therefore uniform. No need to make true breeding.

• offspring are susceptible to the same pests and diseases. Increasing viral load.

Question 16

function of afilia gene and why is it beneficial for a plant?

Answer 16

• determines identity of leaf structure.
• will promote growth of tendrils instead of leaflets.
• tendrils promote binding of many pea plants together to make a bed - increases photosynthesis.

Question 17

what is the benefit of the dwarfing gene?

Answer 17

dwarf cereals are more resistant to lodging and more responsive to N fertilisers.

Question 18

what is the difficulty of breeding for complex traits controlled by many genes?

Answer 18

may take longer to breed for the desired trait. there is no guarantee it will be produced straight away as a whole range of these varying traits will be produced.

Question 19

yield ceiling

Answer 19

reaching a plateau of yield - crossing elite varieties with each other and there is not much genetic variation anymore.

running out of allele combinations to improve yield - have already found the best.

Question 20

how to break yield ceiling

Answer 20

1. grow more hybrids
2. induce more recombination
3. introgress genes from landrace or wild relative

Question 21

marker assisted selection

Answer 21

uses diverse cultivars or landraces as mapping populations.

look for correlation between phenotype and marker genotype

Question 22

how do some plants avoid inbreeding?

Answer 22

1. some only produce one type of flower, male or female.
2. male and female flowers flowering at different times in the year.
3. production of S genes - plant recognises products of these genes (S proteins) and prevents the development of seeds.

Question 23

hybrid vigour

Answer 23

F1 hybrid is more vigorous (bigger and fitter) than both parents.

Question 24

hybrid depression

Answer 24

crosses between two genetically distant groups or populations results in a decrease of fitness.

Question 25

what causes heterosis/hyrbid vigour?

Answer 25

dominance hypothesis: cancelling or masking of deleterious alleles of one parent by a more dominant allele of the other parent. over dominance hypothesis: the heterozygote is superior to either of the homozygotes.

Question 26

why is polyploid so common in crops?

Answer 26

polyploid has more DNA per cell - as the amount of DNA increases so does the size of the cell and in turn the size of the plant.

Question 27

why is it useful that bananas are triploid?

Answer 27

1. odd number polyploidy causes sterility. 2. this means that bananas don't have seeds. 3. this means we can eat them.

Question 28

how does polyploidy occur?

Answer 28

failure of anaphase (3rd stage of cell cycle) means sister chromatids end up in same nucleus and the cell inherits twice the normal number of chromosomes.

Question 29

allopolyploidy

Answer 29

more than two sets of chromosomes that came from to different species - production of a hybrid. opposite of autopolyploidy - more than two sets of chromosomes from two parents of the same species.

Question 30

cisgene

Answer 30

gene added to a species without crossing

Question 31

advantages of gm crops

Answer 31

1. quicker - two generations to homozygosity 2. cleaner - only one gene added 3. not limited to genes present in inter fertile relatives

Question 32

disadvantages of gm crops

Answer 32

1. requires greater knowledge of gene function 2. adverse public opinion 3. no gm for local crops (to feed local population)

Question 33

flavrsavr tomatoes

Answer 33

1. tomatoes get damaged if they are transported ripe. 2. unripe tomatoes treated with ethrel (induces ripening) are transported. 3. these tomatoes are not sweet however they are soft. 4. they then removed PG (responsible for fruit softening) and this meant that the tomatoes ripened but did not get soft.

Question 34

Bt crops

Answer 34

1. Bt protein binds to receptors in the gut of insects and creates a hole in the cells and kills the insect. 2. they moved the Bt proteins into crops.

Question 35

how did they ensure insects didn't become resistant to Bt?

Answer 35

sold 90% bt seeds and 10% susceptible maize seeds. this minimised evolution of insects.

Question 36

roundup case study

Answer 36

1. weeds cause a decrease in yield 2.