1. Bio 3.7 Human Manipulation Of Genetic Transfer
Selective Breeding

2. Student Learning Objectives
One/Many Idea:
Define selective breeding
Describe Inbreeding
Describe Hybridisation
Describe Polyploidy

3. Which of these is/are not genetically manipulated?
Common Wheat
Square Watermelons
Tiger-looking dog
Liger
Killer Bee

4. Genetic Manipulation Genetic Manipulation Selective Breeding
Transgenesis
Genetic Manipulation
Assisted reproduction
Whole organism cloning

5. Selective Breeding
Selective breeding is a method by which humans determine the genetic makeup of organisms by controlling breeding
It involves selecting for certain desirable traits by:
Allowing individuals that have the desired traits to breed
Removing (culling) individuals that do not provide desirable traits from the breeding population
Inbreeding which results in individuals homozygous for a trait
Retain those properties in future generation

6. Selective Breeding Selective Breeding Hybridisation Inbreeding
Repeat breeding of plants and animals with the same desired traits would result in retaining these beneficial properties
Hybridisation
Breeding between closely related species

7. Inbreeding: From Wolf to Woof
The first animal to be domesticated was probably the wolf (10,000 to 15,000 years ago)
Wolf cubs that demonstrated traits of sociability and obedience may have been allowed to remain with groups of humans helping with hunting, guarding and companionship
Overtime, selection for specific traits such as size, speed, behavioural traits..etc lead to a huge variety of breeds for specific tasks

9. Behaviour with other hens
Best Egg
Imagine you work for the super-chick egg company, and it has been decided the Kendo and Bibby have been chosen to mate
Research suggests the following:
Supermarkets want large eggs which are brown with yellow yolks
Farmers want passive livestock which are healthy
What features do you hope will be shown by the offspring?
Kendo male bird
Bibby
female bird
Features
Kendo family
Bibby family
No. eggs per week 6 4
Colour of eggs
White
Brown
Size of eggs
Medium
Large
Colour of yolk
Bright yellow
Pale lemon
Resistance to disease
Highly resistant
Not resistant
Behaviour with other hens
Aggressive
Not aggressive

10. Behaviour with other hens
Super Eggs
Kendo male bird
Bibby
female bird
Features
Kendo family
Bibby family
No. eggs per week 6 4
Colour of eggs
White
Brown
Size of eggs
Medium
Large
Colour of yolk
Bright yellow
Pale lemon
Resistance to disease
Highly resistant
Not resistant
Behaviour with other hens
Aggressive
Not aggressive
You would want the following features:
6 eggs
Brown eggs
Large eggs
Bright yellow yolk
Highly resistant
Not aggressive
However there are not guarantees that the offspring will carry all these traits

11. Development of Crop Species
Most modern crop plants are very different from their wild ancestors
Two main process have occurred in the past to speed up the development of many staple foods:
Hybridisation
Polyploidy

12. Hybridisation
Plants hybridise very easily with closely related species to retain desirable traits from both species. Most of these hybrids are sterile but may become fertile by the process of polyploidy
Hybrids are sterile: different number of chromosomes and fail to segregate during meiosis and result in sterile

13. Polyploidy
Polyploidy is the sate of having three or more complete sets of chromosomes
It is resulted from the failure of separating chromosome pairs (non-disjunction)
This state has the benefits of both creating fertile hybrids and the over-expression of certain traits such as seed number or fruit size
N = one set of chromosomes, 2N is the “normal state” in most animals. Plants

14. Hybrid and Polyploidy
Scenario 1
Scenario 2

15. Wheat
Common wheat has developed as a result of several polyploid events after the formation of hybrids between different grass species:
Goat Grass
Genome: DD 2N 14 X
Wild Grass
Genome: BB 2N 14
Interbreed to form sterile hybrid X
Chromosome doubling (polyploidy) makes hybrid viable
Interbreed to form sterile hybrid
Emmer Wheat
Genome:
AABB 4N 28
Domesticated in the Middle East
Chromosome doubling (polyploidy) makes hybrid viable
Common Wheat
Genome:
AABBDD 6N 42
Wild Einkorn
Genome: AA 2N 14
Einkorn
Genome: AA 2N 14

16. Hybridisation Examples
Wheat
Modern wheat is hexaploid (6N) and has developed from two hybridisations and two occurrences of polypolids
Bananas
Common cavendish bananas are triploid (3N) which results from hybridisation thousands of years ago.
These banana plants are seedless and sterile
Luckily bananas are easily grown from cuttings

17. Work/Homework
Workbook, page 234