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Bio 3.7 Human Manipulation Of Genetic Transfer. Selective Breeding. Student Learning Objectives. One/Many Idea: Define selective breeding Describe Inbreeding Describe Hybridisation Describe Polyploidy . Which of these is/are not genetically manipulated?. Square Watermelons. Common Wheat.

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student learning objectives
Student Learning Objectives

One/Many Idea:

  • Define selective breeding
  • Describe Inbreeding
  • Describe Hybridisation
  • Describe Polyploidy
which of these is are not genetically manipulated
Which of these is/are not genetically manipulated?

Square Watermelons

Common Wheat

Tiger-looking dog

Killer Bee


genetic manipulation
Genetic Manipulation

Selective Breeding


Genetic Manipulation

Assisted reproduction

Whole organism cloning

selective breeding
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 breeding1
Selective Breeding



Repeat breeding of plants and animals with the same desired traits would result in retaining these beneficial properties


Breeding between closely related species

inbreeding from wolf to woof
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
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


female bird

super eggs
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


female bird

development of crop species
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

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

  • 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 polyploidy
Hybrid and Polyploidy

Scenario 2

Scenario 1










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

Chromosome doubling (polyploidy) makes hybrid viable

Interbreed to form sterile hybrid

Domesticated in the Middle East

Chromosome doubling (polyploidy) makes hybrid viable

hybridisation examples
Hybridisation Examples


  • Modern wheat is hexaploid (6N) and has developed from two hybridisations and two occurrences of polypolids


  • 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