selective breeding and genetic engineering

SELECTIVE BREEDING SELECTIVE BREEDING & GENETIC & GENETIC

ENGINEERINGENGINEERING

Selective Breeding & Genetic Selective Breeding & Genetic EngineeringEngineering

►Selective breeding & genetic Selective breeding & genetic engineering are 2 scientific techniques engineering are 2 scientific techniques in which humans try to produce in which humans try to produce offspring with desirable traitsoffspring with desirable traits

What is selective breeding?What is selective breeding?►DefinitionDefinition::

Selective breeding is where Selective breeding is where humans select (chose) 2 humans select (chose) 2 animals with desired traits & animals with desired traits & breed (mate) them trying to breed (mate) them trying to produce offspring with the produce offspring with the desired traits of both parentsdesired traits of both parents

Selective BreedingSelective Breeding►TypicallyTypically, strains which , strains which areare selectively selectively

bred are bred are domesticateddomesticated►Over many generationsOver many generations, the practice , the practice

leads to the development of strains leads to the development of strains with the desired characteristicswith the desired characteristics

Example of Selective Breeding Example of Selective Breeding in Cattlein Cattle

Brahman cattle: good resistance toheat, but poor meat

English shorthorn cattle: good beef, but poorheat resistance

When selecting to breedthese 2 animals we get aSanta Gertrudis cattle

Result = good beef ANDresistant to heat

How did the liger appear?How did the liger appear?► If the father is a lion & the mother is a If the father is a lion & the mother is a

tiger, the offspring are known as ligers tiger, the offspring are known as ligers and the pairing results in gigantismand the pairing results in gigantism

Strong but lacks speed

Fast but notas strong

Ligers are fast & strong& twice as big as parent

Pros of Selective BreedingPros of Selective Breeding►BenefitsBenefits::

Farmers can produce crops with higher Farmers can produce crops with higher yieldyield

►More fruit or vegetables on a stalkMore fruit or vegetables on a stalk Farmers can produce animals that grow Farmers can produce animals that grow

more meat, more milk, more eggs, faster more meat, more milk, more eggs, faster & stronger& stronger

Can produce friendlier and prettier petsCan produce friendlier and prettier pets

ConsCons of Selective Breeding of Selective Breeding►DisadvantagesDisadvantages::

Loss of genes in a populationLoss of genes in a population► By not allowing some animals to breed, their genes could By not allowing some animals to breed, their genes could

be lost forever in a populationbe lost forever in a population► Take Hitler for example, he tried to kill all Jews, therefore, Take Hitler for example, he tried to kill all Jews, therefore,

trying to eliminate the genes and all Jews from the planettrying to eliminate the genes and all Jews from the planet Animal discomfortAnimal discomfort

► Farmers breed cows to have large utters, so now some Farmers breed cows to have large utters, so now some cows have difficulty walking & have health problemscows have difficulty walking & have health problems

► Some chickens are too heavy to stand, so they have to lay Some chickens are too heavy to stand, so they have to lay down all the timedown all the time

Can lead to inbreedingCan lead to inbreeding► In order to create a certain type of animal through In order to create a certain type of animal through

selective breeding, sometimes brothers & sisters of a selective breeding, sometimes brothers & sisters of a population will mate to pass on favorable traits, and this population will mate to pass on favorable traits, and this can lead to bad health problems for children of inbreedingcan lead to bad health problems for children of inbreeding

GENETIC ENGINEERINGGENETIC ENGINEERING►Genetic engineering is a lot like Genetic engineering is a lot like

selective breeding but a much faster selective breeding but a much faster processprocess

►Definition: taking favorable genes Definition: taking favorable genes from one organism and implanting it from one organism and implanting it into another organism’s DNAinto another organism’s DNA This This can only be done in a laboratory can only be done in a laboratory with with

special equipmentspecial equipment

HOWHOW

AQA Science © Nelson Thornes Ltd 2006 10


Remind me about genes Remind me about genes againagain

A human cell nucleus contains 46 chromosomes.A human cell nucleus contains 46 chromosomes.These chromosomes are made from DNA.These chromosomes are made from DNA.Along the length of the chromosome are genesAlong the length of the chromosome are genes..One of these genes codes for the hormone One of these genes codes for the hormone insulininsulin


It took decades of research to find out which It took decades of research to find out which chromosome contained the insulin gene and where chromosome contained the insulin gene and where

the insulin gene was in that chromosome.the insulin gene was in that chromosome.Finally the insulin gene was cut out of the chromosome Finally the insulin gene was cut out of the chromosome

using a using a restriction enzyme restriction enzyme that leaves that leaves “sticky ends”“sticky ends”

Genetic engineeringGenetic engineering

Sticky ends



First the bacterium was cut open using lysozyme First the bacterium was cut open using lysozyme enzymeenzyme

Then the same Then the same restriction enzyme restriction enzyme that was used to that was used to remove the insulin gene is used to cut into the remove the insulin gene is used to cut into the

plasmid leaving matching sticky endsplasmid leaving matching sticky ends

First the bacterium is cut open using lysozyme enzyme and the plasmid is removed

plasmid

Sticky ends



The sticky ends on the insulin gene and the plasmid The sticky ends on the insulin gene and the plasmid DNA are matched up and joined using another enzyme DNA are matched up and joined using another enzyme called called Ligase.Ligase.

Ligase is rather like DNA glueLigase is rather like DNA glue


Bacteria multiply rapidly and produce many Bacteria multiply rapidly and produce many millions of copies of themselves, all able to make millions of copies of themselves, all able to make

insulin using the incorporated insulin gene.insulin using the incorporated insulin gene.



Bacteria multiply rapidly and produce many Bacteria multiply rapidly and produce many millions of copies of themselves, all able to make millions of copies of themselves, all able to make

insulin using the incorporated insulin gene.insulin using the incorporated insulin gene.


ExamplesExamples of Genetic of Genetic EngineeringEngineering

1.1. People have taken the insulin making People have taken the insulin making gene from humans and inserted it gene from humans and inserted it into bacteria causing bacteria to into bacteria causing bacteria to make human insulinmake human insulin

► Why?Why?► Bacteria can reproduce quickly causing them Bacteria can reproduce quickly causing them

to produce insulin at a much faster rateto produce insulin at a much faster rate

Examples of Genetic Examples of Genetic EngineeringEngineering

2.2. People have taken bad genes (genes People have taken bad genes (genes which cause cancer and other which cause cancer and other diseases) out of a person and diseases) out of a person and inserted healthy genes into a person inserted healthy genes into a person to cure them of diseasesto cure them of diseases

► However, they may be cured of that However, they may be cured of that disease but get another worse disease disease but get another worse disease because of being implanted with the because of being implanted with the other geneother gene

Examples of Genetic Examples of Genetic EngineeringEngineering

4.4. People have inserted genes into People have inserted genes into crops to make the crops resistant crops to make the crops resistant (poisonous) to pests, but are (poisonous) to pests, but are harmless to humans (we think)harmless to humans (we think)

Genetically Engineered Genetically Engineered ChickensChickens

►We have inserted genes into chickens We have inserted genes into chickens to make them grow twice as big and to make them grow twice as big and twice as fast. They are so big they twice as fast. They are so big they can’t walk.can’t walk.

Genetic EngineeringGenetic Engineering

►Genetic engineering Genetic engineering may work may work wonders but wonders but it is all a process of it is all a process of manipulating the naturalmanipulating the natural

The Pros & Cons of The Pros & Cons of Genetic EngineeringGenetic Engineering

ProsPros Include: Include:1.1. Humans have made crops with better Humans have made crops with better

taste, nutrition, and growth ratetaste, nutrition, and growth rate2.2. Humans have made pest resistant crops Humans have made pest resistant crops

and crops with longer shelf lifeand crops with longer shelf life3.3. Humans have been able to produce new Humans have been able to produce new

foodsfoods► Foods which couldn’t be reproduced in Foods which couldn’t be reproduced in

naturenature4.4. Humans can help cure certain diseaseHumans can help cure certain disease5.5. Boosts positive traits and suppress Boosts positive traits and suppress

negative onesnegative ones

ConsCons Include: Include:1.1. By making plants bigger, taste better, and By making plants bigger, taste better, and

better appearance we have accidentally better appearance we have accidentally made some crops allergenic to peoplemade some crops allergenic to people

2.2. By making plants bigger, taste better, and By making plants bigger, taste better, and better appearance we have accidentally better appearance we have accidentally made some crops have less nutritional valuemade some crops have less nutritional value

3.3. Accidental gene transferAccidental gene transfer► Such as when we inserted genes into crops to Such as when we inserted genes into crops to

make them resistant to pest or herbicides, the make them resistant to pest or herbicides, the genes leaked over into weeds and made them genes leaked over into weeds and made them resistant to pest and herbicides tooresistant to pest and herbicides too

ConsCons Include: Include:4.4. Genetic engineering in human beings can Genetic engineering in human beings can

have certain side effectshave certain side effects► While treating one defector disease, the genetic While treating one defector disease, the genetic

engineering may lead to another disease which engineering may lead to another disease which could be worsecould be worse

5.5. What’s next?What’s next?► Will people try to insert genes into babies to have Will people try to insert genes into babies to have

children which are smarter, muscular, prettier, children which are smarter, muscular, prettier, certain color eyes, certain color hair, and talentedcertain color eyes, certain color hair, and talented

6.6. Playing God…Playing God…

QuizQuiz1.1. Define selective breeding.Define selective breeding.2.2. List 3 examples of selective breeding.List 3 examples of selective breeding.3.3. List 2 benefits of selective breeding.List 2 benefits of selective breeding.4.4. List 2 disadvantages of selective List 2 disadvantages of selective

breeding.breeding.5.5. Define genetic engineering.Define genetic engineering.6.6. List 3 examples of genetic engineering.List 3 examples of genetic engineering.7.7. List 2 benefits of genetic engineering.List 2 benefits of genetic engineering.8.8. List 2 disadvantages of genetic List 2 disadvantages of genetic

engineering.engineering.

Date post:	08-Jan-2017
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