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the green planet 2 > sex genes and agriculture > Flashcards

sex genes and agriculture Flashcards

1
Q

2nd agricultural revolution

A
  1. inventions
  2. breeding
  3. crop rotation
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2
Q

3rd agricultural revolution

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

what is a hectare in metre squared

A

10,000 m2

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4
Q

why is there a higher yield per area?

A
  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
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5
Q

pressures on agricultural systems

A
  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
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6
Q

what do humans need to eat in their diet?

A
  • carbs
  • fats
  • proteins
  • fibre
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7
Q

what is the most traded crop?

A
  1. maize
  2. rice
  3. wheat
  4. potato
  5. cassava
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8
Q

breeding

A

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

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9
Q

propagation

A

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

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10
Q

how do annual plants grow?

A

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

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11
Q

how do perennial plants grow?

A

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

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12
Q

how do tubers grow?

A

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

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13
Q

what is an example of vegetative propagation?

one advantage of this

A

marram grass on sand dunes.

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

ADVANTAGE - no risks that come with sex.

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14
Q

grafting

A

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

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15
Q

advantages and disadvantages of clonal propagation

A

+ 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.
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16
Q

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

A
  • 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.
17
Q

what is the benefit of the dwarfing gene?

A

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

18
Q

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

A

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.

19
Q

yield ceiling

A

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.

20
Q

how to break yield ceiling

A
  1. grow more hybrids
  2. induce more recombination
  3. introgress genes from landrace or wild relative
21
Q

marker assisted selection

A

uses diverse cultivars or landraces as mapping populations.

look for correlation between phenotype and marker genotype

22
Q

how do some plants avoid inbreeding?

A
  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.
23
Q

hybrid vigour

A

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

24
Q

hybrid depression

A

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

25
Q

what causes heterosis/hyrbid vigour?

A

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.

26
Q

why is polyploid so common in crops?

A

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.

27
Q

why is it useful that bananas are triploid?

A
  1. odd number polyploidy causes sterility.
  2. this means that bananas don’t have seeds.
  3. this means we can eat them.
28
Q

how does polyploidy occur?

A

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.

29
Q

allopolyploidy

A

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.

30
Q

cisgene

A

gene added to a species without crossing

31
Q

advantages of gm crops

A
  1. quicker - two generations to homozygosity
  2. cleaner - only one gene added
  3. not limited to genes present in inter fertile relatives
32
Q

disadvantages of gm crops

A
  1. requires greater knowledge of gene function
  2. adverse public opinion
  3. no gm for local crops (to feed local population)
33
Q

flavrsavr tomatoes

A
  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.
34
Q

Bt crops

A
  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.
35
Q

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

A

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

36
Q

roundup case study

A
  1. weeds cause a decrease in yield
    2.

the green planet 2 (10 decks)

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