GENETIC ENGINEERINGChapter 13

CHANGING THE LIVING WORLD13-1

SELECTIVE BREEDING Selective breeding – (artificial selection)

Breeders select individuals with desirable traits to breed.

Offspring inherit desirable traits from parents (hopefully).

SELECTIVE BREEDING

Luther Burbank used selective breeding to develop Shasta daisies, a popular variety.

SELECTIVE BREEDING Hybridization

Crossing dissimilar individuals to produce offspring with “hybrid vigor”.

HYBRIDIZATION

A mule is a cross between a horse and a donkey.

SELECTIVE BREEDING Inbreeding

Crossing similar individuals to maintain desired traits.

INBREEDING

Inbreeding maintains the desirable traits of Labradors, but may make the breed more susceptible to disease and physical abnormalities.

which crosses

consists of

Selective Breeding

for example

Inbreeding Hybridization

Similar organism

sDissimilar organism

sfor example

Organism breed A

Organism breed A

Organism breed B

Retains desired

characteristicsCombines desired

characteristics

which

which crosses

which

Section 13-1

Concept Map

INCREASING VARIATION Inducing mutations increases variation in a

population. Variation in a population is a good thing. Radiation and chemicals are used.

INDUCING MUTATIONS

Bacteria have been induced to digest oil.

INDUCED MUTATIONS

Strawberries have been induced to be polyploid making bigger, sweeter strawberries.

MANIPULATING DNA13-2

GENETIC ENGINEERING Making changes in the genetic code.

TOOLS OF MOLECULAR BIOLOGY

DNA Extraction lyses the cells (detergent), then separates the DNA from protein histones using a protease enzyme. Lastly the DNA is precipitated.

TOOLS OF MOLECULAR BIOLOGY

Restriction Enzymes cut DNA into fragments at certain base sequences. Restriction enzymes only cut their specific sequence.

Recognition sequences

DNA sequence

Restriction Enzymes

Recognition sequences

DNA sequence

Restriction enzyme EcoRI cuts the DNA into fragments. Sticky end

Section 13-2

Restriction Enzymes

TOOLS OF MOLECULAR BIOLOGY

Gel Electrophoresis Separates DNA fragments based on size. An electric current pulls the fragments across a gel and produces a unique “fingerprint”. Used in forensics

DNA plus restriction enzyme

Mixture of DNA fragments

Gel

Power source

Longer fragments

Shorter fragments

Figure 13-6 Gel Electrophoresis

USING THE DNA SEQUENCE

In DNA Sequencing DNA polymerase and fluorescent labeled nucleotides determine the order of bases in a fragment.

Figure 13-7 DNA Sequencing

USING THE DNA SEQUENCE

In gene splicing DNA is cut into fragments and pasted together to create recombinant DNA

USING THE DNA SEQUENCE

Polymerase Chain Reaction (PCR) makes unlimited copies of a gene.

DNA polymerase adds complementary strand

DNA heated to separate strands

DNA fragment to be copied

PCRcycles 1DNAcopies 1

2

2

3

4

4

8

5 etc.

16 etc.

Figure 13-8 PCR

CELL TRANSFORMATION13-3

CELL TRANSFORMATION When a bacterial cell takes in DNA from

outside the cell, the external DNA gets incorporated into the bacterium’s own DNA. Recombinant DNA has been made. The cell has been transformed. It will make a

new protein(s).

TRANSFORMING BACTERIA Bacterial plasmids (circular DNA) are used

to produce human hormones (HGH, insulin, clotting factor). Plasmids are useful because they are readily

taken in by bacteria and they easily replicate within a cell.

Also genetic markers in the plasmid help isolate transformed cells from non-transformed cells. Typically the gene for resistance to antibiotics is used

as a genetic marker. After transformation, the culture is treated with an antibiotic to kill all non-transformed cells.

Human Cell

Gene for human growth hormone

Recombinant DNA

Gene for human growth hormone

Sticky ends

DNA recombination DNA

insertionBacterial Cell

Plasmid

Bacterial chromosome

Bacterial cell for containing gene for human growth hormone

Section 13-3

Figure 13-9 Making Recombinant DNA

TRANSFORMING PLANT CELLS Plant cells don’t readily take in external DNA.

Plant cells are grown in culture with their cells walls removed.

Then plasmids are directly injected into the cells or carried into the cells with a bacterium.

Recombinant plasmid

Gene to be transferred

Agrobacterium tumefaciens

Cellular DNA

Transformed bacteria introduce plasmids into plant cells

Plant cell colonies

Complete plant is generated from transformed cell

Inside plant cell, Agrobacterium inserts part of its DNA into host cell chromosome

Section 13-3

Figure 13-10 Plant Cell Transformation

TRANSFORMING ANIMAL CELLS DNA is injected directly into egg cells. DNA can be carried into cells with viruses.

Once inside the nucleus, recombinant DNA can replace a host cell gene making it possible to treat disorders caused by single genes.

This therapy is called “gene replacement”. Ex: cystic fibrosis

Recombinant DNA

Flanking sequences match host

Host Cell DNATarget gene

Recombinant DNA replaces target gene

Modified Host Cell DNA

Section 13-3

Knockout Genes

APPLICATIONS OF GENETIC ENGINEERING13-4

TRANSGENIC ORGANISMS Transgenic organisms contain genes from

different species. Transgenic bacteria produce human proteins. Transgenic animals grow faster and produce

leaner meat. Transgenic plants are more resistant to disease.

Foods obtained from transgenic organisms are labeled “genetically modified”.

CLONING

A clone is a member of a genetically identical population.In 1997 the first mammal was cloned, a sheep named Dolly.

A donor cell is taken from a sheep’s udder. Donor

NucleusThese two cells are fused using an electric shock. Fused Cell

The fused cell begins dividing normally.

EmbryoThe embryo is placed in the uterus of a foster mother.Foster

Mother

The embryo develops normally into a lamb—Dolly

Cloned Lamb

Egg Cell

An egg cell is taken from an adult female sheep.

The nucleus of the egg cell is removed.

Section 13-4

Figure 13-13 Cloning of the First Mammal