3.2 Plant and Animal breeding Flashcards Preview

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Flashcards in 3.2 Plant and Animal breeding Deck (50)
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1
Q

Why do plant and animal breeders try and develop new and improved varieties of crops and livestock?

A

to provide sustainable food sources

they do this by manipulating or changing the heredity/genetics of an organism

2
Q

REMEMBER!

A

discrete variation - can divide members of a species into distinct groups
continuous variation - changes gradually from one extreme to another

3
Q

What does single gene inheritance control?

A

controls characteristics which show discrete variation

4
Q

what is polygenic inheritance?

A

characteristics which show continuous variation are controlled by several genes.
characteristics which are controlled by polygenic inheritance can also be influenced by the environment

5
Q

REMEMBER!

A

Genetically modified organisms have been reprogrammed by genetic engineering to develop characteristics that are useful to humans

6
Q

Genetic modification

reason for altering genetics, the benefit and an example

A

increase in yield - more food produced - barley
increase in nutritional value - increase in protein content - rice
resistance to disease - crop not damaged by disease - blight resistant potatoes
resistance to pests - crop resistant to insect, fungus or worms - soya been resistance
to survive a particular environment - adapted to grow in a hot, dry environment - corn
to make it more suitable for rearing or harvesting - a more uniform crop height makes harvesting easier, increasing yield - wheat

7
Q

What is a cultivar?

A

a cultivar is a plant that has been created or selected intentionally for desirable characteristics that can be maintained by cultivation.
A cultivar is different from others in at least one characteristic or trait.

8
Q

Example of cultivar?

A

agricultural crops are almost exclusively cultivars

9
Q

What is a field trial?

A

an experimental investigation in an organisms natural environment ( rather than in the lab)

10
Q

Use of field trials?

A

plant field trials used to see whether a particular treatment makes a difference to the crop
measurements such as height, grain size, yield or incidence of disease can be used to determine the effects of a treatment

11
Q

Trials can be used to evaluate what?

A

the performance of different cultivars in a range of environments
the effects of different treatments such as pesticides or fertilisers
genetically modified crops

12
Q

CHECK NOTES FOR AN EXAMPLE

A

13
Q

What do reliable and valid field trials require?

A
  1. careful selection of treatment - if the treatment to be investigated is the effect of fertiliser, the treated plot would be given fertiliser and the control plot would have no fertiliser. all other variables would be kept constant. The treated and untreated plots should be as similar as possible (the same soil moisture and slope) to allow valid comparison of treated and untreated areas.
  2. replicates - use several trial plots to increase the reliability of results. this reduces the effect of variability within samples.
  3. randomisation - the treated and control areas should be scattered randomly across the site of the trial to eliminate the possibility of bias when measuring the effect of the treatment
14
Q

What is a method of increasing food security?

A

to develop new varieties of crops and livestock breeds using breeding programmes

15
Q

What do breeding programmes allow?

A

allow desirable features to be bred into particular plants or animals

16
Q

what are desirable characteristics that increase food security?

A
wheat - high grain yield
potato - resistance to fungal disease
soya bean - high protein content of seeds
strawberry - resistance to frost
dairy cattle - high milk yield
beef cattle - high meat yield
17
Q

TOPTIP

A

phenotype - physical appearance of offspring
genotype - alleles (forms of a gene) carried
dominant alleles - show up in phenotypes
recessive alleles - do not show up in phenotype unless there are no dominant alleles present to make them

18
Q

TOPTIP

A

an organisms genotype is homozygous when it has two identical alleles of a gene it is true breeding

when it has two different alleles of a gene it is heterozygous

19
Q

What are dwarf varieties of cereal?

A

dwarf varieties of some cereal crops with much shorter stems then normal were discovered
these plants put more energy into creating see and were easier to harvest, thus increasing the yield of these crops and improving food security

20
Q

What is selective breeding?

A

plant and animal breeders choose the parent organisms with the desired characteristics and use them in their breeding programme
the aim is to produce offspring with the combined characteristics of the two parents

21
Q

What is outbreeding?

A

outbreeding is the mating of unrelated or distantly related members of a species.
animals and cross pollinating plants are naturally outbreeding

22
Q

What is inbreeding?

A

inbreeding is the mating of closely related individuals

this can happen naturally in self pollinating plants

23
Q

what are inbreeding programmes?

A

in inbreeding programmes, selected plants or animals are bred for several generations until the population breeds due to the elimination of heterozygotes

24
Q

What is inbreeding depression?

A

inbreeding results in homozygosity leading to the accumulation of harmful (deleterious) homozygous alleles and increasing the chances of offspring being affected by recessive traits - this is inbreeding depression

25
Q

What can inbreeding depression result in?

A

loss of vigour and poor general health, reduced fertility or yield

26
Q

What plants are less susceptible to inbreeding depression?

A

self pollinating plants since natural selection eliminates the deleterious alleles over many generations

27
Q

How do breeders avoid inbreeding depression in naturally outbreeding species?

A

by choosing parents with desired characteristics but which are otherwise genetically diverse

28
Q

What is crossbreeding?

A

when a plant or animal is crossed with another organism with a different, but desired genotype, creating offspring with traits from both parents, improving characteristics and producing F1 organisms with hybrid vigour

29
Q

What are F1 hybrids?

A

an F1 hybrid is the cultivar derived from two different parent cultivars
e.g. almost all modern cultivars of edible (seedless) bananas are hybrids of two wild banana species with seeds

30
Q

What are disadvantages of F1 hybrids?

A

a disadvantage of F1 hybrids is the greater cost of seeds
this is because it can take several years to produce inbred lines and non commercial self-pollination often has to be done manually which is time consuming

31
Q

What is a crossbreed?

A

a crossbreed is the result of breeding two different purebred parents of different breeds

32
Q

Example of crossbreeds?

A

Scottish half bred sheep
cross between a cheviot and border leicester breeds
has the large body from border leicester and high muscle mass from cheviot

33
Q

What is mutation breeding?

A

mutation breeding in plants involves exposing seeds to chemicals or radiation in order to generate mutants with desirable traits to breed with other cultivars

34
Q

How has mutation breeding improved certain crops?

A

giving disease resistance, dwarf habit or a change in the chemical or nutritional plant composition

35
Q

TOP TIP

A

genetically true breeding animals command higher market prices when sold as breeding stock

36
Q

What is a testcross?

A

a testcross is used to determine the genotype of an individual with a dominant phenotype to find out if it is homozygous or heterozygous
the organism with the dominant phenotype is crossed with an organism that is homozygous recessive for the same characteristic

37
Q

Why can a testcross be used in a breeding programme?

A

to identify unwanted individuals with heterozygous recessive alleles

38
Q

DONT FORGET

A

genetic engineering is the genetic alteration of a cell by insertion of a gene or genes from another organism this cell has been GM modified producing a GM organism

39
Q

What is a genome?

A

an organisms genome is the full and unique set of genetic instruction in its DNA

40
Q

What is genomic sequencing?

A

is a process which can determine the DNA sequence of an organism’s genome

41
Q

How is the DNA broken up?

A

using enzymes

42
Q

Why are genomic sequencing machines used to sequence the DNA fragments and computer programmes are used?

A

to compare the overlapping sections to recreate the sequence of the original DNA strand

43
Q

What is the purpose of genomic sequencing?

A

allows organism with desirable genes to be identified and used in breeding programmes

44
Q

What is genetic transformation?

A

genetic transformation is the alteration of the genome of a cell by the insertion of a gene or genes from another organism, either naturally or artificially
the transformed genome can then be used in breeding programmes

45
Q

What are GM crops are useful for?

A

protection from threats such as low temperatures, insects and viruses
increasing nutritional value or yield
increasing tolerance of salt or drought
reducing the need for as much fertiliser or pesticide

46
Q

What is BT toxin?

A

the soil bacterium bacillus thuringiensis (Bt) produces a protein (Bt toxin) which is toxic to certain insects
when eaten the toxin is activated and destroys the insect’s gut
there are different strains of BT toxin which are effective against different insect pests
Scientists can remove the BT toxin gene from bacteria and insert it into plants, allowing plants to produce their own toxin which offers protection against damage by insects
this removes the need to use chemical insecticides

47
Q

What is glyphosphate?

A

Glyphophate is a herbicide (weedkiller) which is particularly effective against broadleaf weeds and grasses that compete with crops
It us an enzyme inhibitor in the production of amino acids and when absorbed through the plant foliage, it is transported to the growing points of the plant, killing it.
Genetically engineered plants that are glyphosphate tolerant can ow be produced
they contain a glyphosphate resistance gene allowing farmers to control weeds without damaging their crop

48
Q

What vitamin is low in rice?

A

Rice is low in vitamin A so in areas where rice is the staple diet vitamin A deficiency and its associated visual defects are prevalent

49
Q

What can be done to sort this deficiency of vitamin A in rice?

A

two genes coding for beta carotene can be inserted into the normal rice genome so that rice plants can make beta carotene which allows us to make vitamin A.

50
Q

What is golden rice?

A

golden rice is a genetically engineered rice cultivar which contains beta carotene and therefore is yellow-orange in colour