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