Bio 3.7 Human Manipulation Of Genetic Transfer Selective Breeding
Feb 23, 2016
Bio 3.7 Human Manipulation Of Genetic Transfer
Selective Breeding
Student Learning ObjectivesOne/Many Idea: Define selective breeding Describe Inbreeding Describe Hybridisation Describe Polyploidy
Which of these is/are not genetically manipulated?
Square Watermelons
Tiger-looking dogCommon Wheat
Liger Killer Bee
Genetic Manipulation
Genetic Manipulation
Selective Breeding
Whole organism cloning
Assisted reproduction
Transgenesis
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
Selective Breeding
Selective Breeding
InbreedingRepeat breeding of plants and animals with the same desired traits would result in retaining these beneficial properties
HybridisationBreeding between closely related species
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
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
Bibbyfemale bird
FeaturesKendo 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
Super Eggs
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
Kendo male bird
Bibbyfemale bird
FeaturesKendo 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
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:1. Hybridisation2. Polyploidy
HybridisationPlants 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
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
Hybrid and PolyploidyScenario 1Scenario 2
Wild GrassGenome: BB
2N 14
Goat GrassGenome: DD
2N 14
Common wheat has developed as a result of several polyploid events after the formation of hybrids between different grass species:
Interbreed to form sterile
hybrid
Domesticated in the Middle East
Interbreed to form sterile
hybrid
X
X
Chromosome doubling
(polyploidy) makes hybrid
viable
Chromosome doubling
(polyploidy) makes hybrid
viableEmmer WheatGenome: AABB
4N 28
EinkornGenome: AA
2N 14
Wild EinkornGenome: AA
2N 14
Common WheatGenome: AABBDD
6N 42
Wheat
Hybridisation ExamplesWheat 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
Work/Homework Workbook, page 234