Domestication

Question 1

Life before domestication?

Answer 1

Hunter gatherer lifestyles are completely dependent on their immediate environment for food (which had to be eaten before it went bad), shelter and clothing.
Pre-plant domestication diet included: acorns, pignuts, seaweed, elderberries, wild boar, fish and birds.

Question 2

How did diet change with climate?

Answer 2

Generally, the more tropical the climate, the more they relied on plant matter for food, like fruit and roots.

Animal food like fish and game were the major energy and nutritional sources for people closer to the poles. In some cases plants contributed very little to the overall caloric intake.

Question 3

Why was the hunter gatherer lifestyle dangerous?

Answer 3

The seasonality of foods (fruits, nuts) made the hunter-gatherer lifestyle very precarious.

Also very labour insensitive, as most of the time is spent looking for good so can only sustain low density populations.

Dangerous as well, due to the fact the hunter could be predated. This is why agriculture arose.

Question 4

When did the initial domestication steps occur?

Answer 4

10,000 years ago.

In different parts of the world.

Question 5

How many regions did domestication occur in?

Answer 5

Archaelogical evidence suggests 24.

Question 6

Example of a crop that got domesticated in India?

Answer 6

Rice and sugarcane.

Question 7

Define plant domestication?

Answer 7

The genetic modification of a wild species to create a new cultivate plant form altered to meet human needs.

Question 8

What traits can be selected for?

Answer 8

Yield size 
Size 
Appearance 
Longevity 
Colour

Question 9

Why does domestication reduce genetic diversity?

Answer 9

Genetic bottleneck - reduced phenotypic diverisity.

Question 10

Timeline of domestication?

Answer 10

10,000 years ago – initial domestication, unconscious selection and propagation of plants with desirable traits
BC – conscious cultivation of plants with desired traits
1700 – deliberate breeding to improve traits
1900 – genetic mechanism known
2000 – genetic manipulation

Question 11

How did wheat change when domesticated?

Answer 11

From wild grass.

Much larger ears and grain size. More robust.

Question 12

How did potatoes change when domesticated?

Answer 12

Larger, more uniform. Less variability in colour.

Question 13

How did strawberries change when domesticated?

Answer 13

The metabolism changed, selecting for sweeter fruits.

Question 14

What is the domestication syndrome?

Answer 14

Properties which distinguish a crop from its wild progenitor.
A collection of phenotypic traits associated with the genetic change to a domesticated form.

• larger fruits/grains
• fewer fruits/grains
• decrease in bitter substances in edible structures
• changes in photoperiod sensitivity
• loss of natural seed dispersal
• changed growth form so more robust
• loss of seed dormancy
• coordinated germination
• increased sugar

Question 15

Gene changes in maize?

Answer 15

Increased number of kernels and size compared to teosinte.

TB1 gene variation explains this. TB1 encodes a growth transcription factor which regulates gene expression.

In teosinte, TB1 is expressed in low levels in axillary meristems.

In modern maize, TB1 expressing is elevated relative to teosinte, correlating with repressed branch outgrowth.

Question 16

How did genes change in wheat?

Answer 16

Loss of spike shattering prevents the grains from scattering by wind and facilitates harvesting.

Presence of an active Q gene confers a square shaped spike. Absence of Q results in a longer and spear shaped spike.

Q can differ by an amino aid substitution in the AP2 like protein it encodes.

Question 17

How many genes control domestication traits?

Answer 17

A few genes of large effect.

Question 18

Genetic basis of plant breeding?

Answer 18

• application of genetic analysis to develop plant lines better suited for human purposes
• landraces are locally adapted genotypes
• geographic spread from centres of domestication
• rise of scientific breeding

Question 19

Where did domestication begin?

Answer 19

The fertile crescent is seen as the birthplace of agriculture.

Had a temperate climate with fertile soil and two great rivers.

This is where settled farming first began to emerge as people started the process of clearance and modification of natural vegetation in order to grow newly domesticated plants as crops.

Question 20

Link between crop and animal domestication?

Answer 20

Animal domestication allowed humans to: contain animals with the right temperament, have a steady supply of food, and use animals for companionship, religious purposes and work. In return, the animals were protected and had a constant supply of food. Selective breeding occurred as humans kept animals with desirable traits. Sheep were the first domesticated animal in about 12,000 BCE for their wool and meat.

Question 21

How does scientific breeding happen?

Answer 21

1. Pedigree breeding:
2. Recurrent backcross breeding/Introgression.
3. Hybrid vigour
4. Maize cytoplasmic male sterility
5. Wide crossing

Question 22

How does marker assisted selection work in plant breeding?

Answer 22

MAS is the use of DNA markers tightly linked to target loci to assist phenotypic screening.

The advantage of MAS is that it’s a simple molecular biology method, selection at seedling stage, reliable, high throughput, genotyping, reduced costs associated with screening for traits 
Either RFLP (Restriction Fragment Length Polymorphism) or SSR (Simple Sequence Repeat) profiling  
The perfect marker has a close linkage to the trait of interest.

Question 23

Risks of GM to human health and the environment?

Answer 23

– Alteration in nutritional profile 
– Introduction of toxins 
– Introduction of allergens 
– Horizontal gene transfer 
– Effect on non-target organisms
– Development of resistance by pests

Question 24

Use of bt?

Answer 24

A common soil protein which produces proteins toxic to insects.
Spores of the soil bacterium contain a crystalline protein which breaks down and releases a toxin that kills insect gut cells once in the guys.

Question 25

Social concerns with GM?

Answer 25

– Unfamiliarity with the technology 
– Lack of information 
– Negative press opinion 
– Opposition by GM activist groups 
– Mistrust of the industry