Genetic Engineering Biology Ch.15. Selective Breeding Selective breeding allows only those organisms...

Genetic Engineering

Biology

Ch.15

Selective Breeding

• Selective breeding allows only those organisms with desired characteristics to produce the next generation.

• Nearly all domestic animals and most crop plants have been produced by selective breeding.

Copyright Pearson Prentice Hall

Selective Breeding

• Humans use selective breeding to pass desired traits on to the next generation of organisms.


htt

p://

ww

w.w

isd

om

pa

ne

lpro

.com

/vie

w/b

in/im

age

s/d

og_

his

tory

_tr

ee.

jpg

Selective Breeding

• Hybridization – the crossing of dissimilar individuals to bring

together the best of both organisms. – Hybrids, the individuals produced by such

crosses, are often hardier than either of the parents.


Selective Breeding

• Inbreeding – the continued breeding

of individuals with similar characteristics.

– Inbreeding helps to ensure that the characteristics that make each breed unique will be preserved.

– Serious genetic problems can result from excessive inbreeding.


http://www.geneticstimes.com/Images/German_shepherd.JPG

Increasing Variation

• Breeders increase the genetic variation in a population by inducing mutations.

• Mutations occur spontaneously, but breeders can increase the mutation rate by using radiation and chemicals.

• Breeders can often produce a few mutants with desirable characteristics that are not found in the original population.




• Producing New Kinds of Bacteria– Introducing mutations has allowed scientists

to develop hundreds of useful bacterial strains, including bacteria that can clean up oil spills.



• Producing New Kinds of Plants– Mutations in some plant cells produce cells

that have double or triple the normal number of chromosomes.

– This condition, known as polyploidy, produces new species of plants that are often larger and stronger than their diploid relatives.

– Polyploidy in animals is usually fatal.

The Tools of Molecular Biology

• Scientists use their knowledge of the structure of DNA and its chemical properties to study and change DNA molecules.




• Scientists use different techniques to:– extract DNA from cells– cut DNA into smaller pieces– identify the sequence of bases in a DNA

molecule– make unlimited copies of DNA



• In genetic engineering, biologists make changes in the DNA code of a living organism.



• DNA Extraction– DNA can be extracted from most cells by a

simple chemical procedure.– The cells are opened and the DNA is

separated from the other cell parts.



• Cutting DNA – Most DNA molecules are too large to be

analyzed, so biologists cut them into smaller fragments using restriction enzymes.

• Enzymes found in bacteria used to destroy phage DNA


• Each restriction enzyme cuts DNA at a specific sequence of nucleotides.

The Tools of Molecular Biology• Separating DNA

– In gel electrophoresis, DNA fragments are placed at one end of a porous gel, and an electric voltage is applied to the gel.

– When the power is turned on, the negatively-charged DNA molecules move toward the positive end of the gel.

BIOLOGY: CONCEPTS AND CONNECTIONS 4th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2003.


• DNA Fingerprinting– A method of

developing a person’s DNA “profile,” similar to a fingerprint.

– Pioneered in England in 1984 by Dr. Alec Jeffreys

Dr. Alec Jeffreys

How does it work?

• 99.9% of your DNA is the same as everyone else’s.

• The 0.1% that differs are a combination of:– Gene differences (Differences in the genes

themselves)– Differences in “polymorphic regions” between

the genes on the DNA.

How does it work?

• Certain points between the genes on the DNA have repeating base sequences.– For example:

ATTACGCGCGCGCGCGCGCTAGC– These are called variable number tandem

repeats (VNTRs for short)

How does it work?

• Everyone has VNTRs at the same place in their DNA, but they are different lengths for different people.– For example:

Person 1: ATTACGCGCGCGCGCGCGTAGC(7 repeats)

Person 2: ATTACGCGCGCGCGTAGC(5 repeats)

Using the DNA Sequence

• These enzymes also make it possible to take a gene from one organism and attach it to the DNA of another organism.

• Such DNA molecules are sometimes called recombinant DNA.


BIO

LO

GY

: CO

NC

EP

TS

AN

D C

ON

NE

CT

ION

S 4

th

Edi

tion

, b

y C

am

pb

ell,

Re

ece

, M

itch

ell,

an

d T

aylo

r,

©2

003

.



• Making Copies – Polymerase chain reaction (PCR) is a

technique that allows biologists to make copies of genes.

– A biologist adds short pieces of DNA that are complementary to portions of the sequence.

http://www.dnalc.org/ddnalc/resources/shockwave/pcranwhole.html


• DNA is heated to separate its two strands, then cooled to allow the primers to bind to single-stranded DNA.

• DNA polymerase starts making copies of the region between the primers.


Genomic DNA

Targetsequence

5

3

3

5

5

3

3

5

Primers

Denaturation:Heat brieflyto separate DNAstrands

Annealing:Cool to allowprimers to formhydrogen bondswith ends oftarget sequence

Extension:DNA polymeraseadds nucleotides tothe 3 end of eachprimer

Cycle 1yields

2molecules

Newnucleo-

tides

Cycle 2yields

4molecules

Cycle 3yields 8

molecules;2 molecules

(in white boxes)match target

sequence

Genomic DNA

Targetsequence

5

3

3

5

5

3

3

5

Primers

Denaturation:Heat brieflyto separate DNAstrands

Annealing:Cool to allowprimers to formhydrogen bondswith ends oftarget sequence

Extension:DNA polymeraseadds nucleotides tothe 3 end of eachprimer

Cycle 1yields

2molecules

Newnucleo-

tides

Cycle 2yields

4molecules

Cycle 3yields 8

molecules;2 molecules

(in white boxes)match target

sequence

http://www.dnalc.org/resources/animations/pcr.html

Transforming Bacteria

• During transformation, a cell takes in DNA from outside the cell. The external DNA becomes a component of the cell's DNA.

Copyright Pearson Prentice Hall htt

p://

bio

log

y20

0.g

su.e

du/h

oug

hto

n/4

56

4%

20

%27

04

/fig

ure

s/le

ctu

re%

20

3/

tra

nsfo

rma

tion.

jpg


• Foreign DNA is first joined to a small, circular DNA molecule known as a plasmid.

• Plasmids are found naturally in some bacteria and have been very useful for DNA transfer.


Plasmids

• Short, circular DNA molecules outside the chromosome

• Carry genes that are beneficial but not essential

• Replicate independently of chromosome

en.wikipedia.org/?title=Plasmid



• The plasmid has a genetic marker—a gene that makes it possible to distinguish bacteria that carry the plasmid (and the foreign DNA) from those that don't.


How do you know which cells have been transformed?


Transforming Plant Cells

• How can you tell if a transformation experiment has been successful?

• If transformation is successful, the recombinant DNA is integrated into one of the chromosomes of the cell.


• In nature, a bacterium exists that produces tumors in plant cells.

• Researchers can inactivate the tumor-producing gene found in this bacterium and insert a piece of foreign DNA into the plasmid.

• The recombinant plasmid can then be used to infect plant cells.



• When their cell walls are removed, plant cells in culture will sometimes take up DNA on their own.

• DNA can also be injected directly into some cells.

• Cells transformed by either procedure can be cultured to produce adult plants.


Transforming Animal Cells

• Many egg cells are large enough that DNA can be directly injected into the nucleus.

• Enzymes may help to insert the foreign DNA into the chromosomes of the injected cell.

• DNA molecules used for transformation of animal and plant cells contain marker genes.

http://www.rikenresearch.riken.jp/images/figures/hi_3609.jpg

Transforming Animal Cells• Gene Therapy

– DNA molecules can be constructed with two ends that will sometimes recombine with specific sequences in the host chromosome.

– The host gene normally found between those two sequences may be lost or replaced with a new gene.


http://library.thinkquest.org/28000/media/genetherapy/l_gene.therapy-ms.gif

Applications of Genetic Engineering

Transgenic Organisms

• An organism described as transgenic, contains genes from other species.


htt

p://

h

ttp:

//w

ww

.bio

.mia

mi.e

du/~

cma

llery

/150

/ha

ndo

uts

/c17

x5tr

an

sgen

ic-t

oba

cco

.jpg

http://www.bio.miami.edu/~cmallery/150/handouts/D.zebra.htm


• Genetic engineering has spurred the growth of biotechnology.– Transgenic animals and plants– The Human Genome Project– The production of vaccines, cancer drugs, and

pesticides– Engineered bacteria that can clean up toxic wastes– Cloning

• Organ replacement



• Transgenic bacteria produce important substances useful for health and industry. Transgenic bacteria have been used to produce:– insulin– growth hormone– clotting factor


BIO

LO

GY

: CO

NC

EP

TS

AN

D C

ON

NE

CT

ION

S 4

th E

diti

on,

by

Ca

mp

be

ll, R

ee

ce,

Mitc

he

ll, a

nd

Tay

lor,

©2

00

3.


• Transgenic animals have been used to study genes and to improve the food supply.

• Mice have been produced with human genes that make their immune systems act similarly to those of humans. This allows scientists to study the effects of diseases on the human immune system.


htt

p://

ww

w.n

cbi.n

lm.n

ih.g

ov/b

oo

ksh

elf/

br.f

cgi?

bo

ok=

cme

d&

part

=A

953

8

Transgenic Animals

• Nils Lonberg, director at Medarex, bred two genetically modified mice, creating a mouse with a humanized immune system.

• In response to disease-causing agents, these mice make human antibodies in their cells, some of which might be developed into drugs.

http://images.businessweek.com/ss/06/01/critters/source/4.htm


• Researchers are trying to produce transgenic chickens that will be resistant to the bacterial infections that can cause food poisoning.

Copyright Pearson Prentice Hall http://www.cals.ncsu.edu/agcomm/magazine/spring03/images/transgenic1.jpg



• Transgenic plants are now an important part of our food supply.

• Many of these plants contain a gene that produces a natural insecticide, so plants don’t have to be sprayed with pesticides.

Transgenic Plants

• Bt Corn– Engineering resistant

corn. Following the insertion of a gene from the bacteria Bacillus thuringiensis, corn becomes resistant to corn borer infection. This allows farmers to use fewer insecticides

http://www.scq.ubc.ca/bt-corn-is-it-worth-the-risk/

htt

p://

ww

w.b

io.d

avi

dso

n.e

du/p

eo

ple

/ka

ber

nd

/se

min

ar/

20

04

/GM

eve

nts

/LH

/cor

ne

ar.

jpg

• “Golden rice” has been genetically modified to contain beta-carotene

– This rice could help prevent vitamin A deficiency

Figure 12.18B

Cloning

• A clone is a member of a population of genetically identical cells produced from a single cell.

• In 1997, Ian Wilmut cloned a sheep called Dolly.


Dolly and Bonnie

Cloning

Cloning

• Researchers hope cloning will enable them to make copies of transgenic animals and help save endangered species.


htt

p://

reso

urc

es.

ed

b.g

ov.h

k/b

iolo

gy/

eng

lish

/ima

ges

/ge

net

ics/

pan

da

.gif


Cloning

• Studies suggest that cloned animals may suffer from a number of genetic defects and health problems.– Abnormal gene expression– “old” DNA

• Our new genetic knowledge will affect our lives in many ways

• The deciphering of the human genome, in particular, raises profound ethical issues– Many scientists have

counseled that we must use the information wisely

DNA technology raises important ethical questions

Figure 12.21A-C

• Genetic engineering involves some risks– Possible ecological damage

from pollen transfer between GM and wild crops

– Pollen from a transgenic variety of corn that contains a pesticide may stunt or kill monarch caterpillars

Could transgenics harm human health or the environment?

Figure 12.20A, B

Date post:	25-Dec-2015
Category:	Documents
Upload:	debra-jackson
View:	221 times
Download:	0 times

Genetic Engineering Biology Ch.15. Selective Breeding Selective breeding allows only those organisms...

Documents