Chapter 13Genetic Engineering

Changing the Living World

1. Selective Breeding: • Selective breeding allowing only the

organisms with desired traits to breed– Takes advantage of naturally occurring variation– Ex: domestic dogs, cats, farm animals, most crops

Cont. Selective Breeding• Hybridization crossing dissimilar

individuals & bringing together the best of both organisms– Hybrids usually hardier than either of

the parents– Ex: crossing disease resistance with

food production

• Inbreeding continued breeding of individuals with similar characteristics– Increased risk of genetic defects– Ex: maintaining characteristics in

breeds of dogs

Ever wondered what a human-dog hybrid would look like?!?!

Human-Dog hybrid was a sculpture created by an Australian artist named Patricia Piccinini.

Increasing Variation

• Breeders increase variation by inducing mutations (*** ultimate source of variation)

• New kinds of bacteria produced by treating them with chemicals and radiation - Results: bacteria that can digest oil used to clean up oil spills

Cont. Increasing Variation

• New kinds of plants produced by treating them with drugs that prevent chromosome separation during meiosis

- Results: polyploidy cells plants larger and stronger (LETHAL in animals!)

Manipulating DNA• Genetic engineering making changes in the DNA code of an organism 1. The Tools of Molecular Biology

a. DNA extraction open cells and separate DNA from other cell partsb. Cutting DNA via restriction enzymes cut DNA into smaller pieces

at a specific sequence of nucleotidesc. Separating DNA via gel electrophoresis mixture of DNA fragments

are put in one end of porous gel and an electric voltage is applied- DNA is negatively charged so the fragments begin to travel toward the positive end of the gel- The smaller the fragment, the faster it travels; the larger/slower

Cutting DNA

Recombinant DNA is DNA taken from two different sources and fused into a single DNA molecule. Special DNA cutting enzymes, called restriction enzymes, cut the DNA at specific sites. Each

restriction enzyme recognizes a different nucleotide sequence. DNA that is cut with a restriction enzyme will have single-stranded ends, called “sticky ends”. Two molecules of DNA cut with the

same restriction enzyme will have the same exposed nucleotides and will undergo complementary base pairing.

Gel Electropheresis

Electrophoresis

Cont. Manipulating DNA

2. Using the DNA Sequence a. Reading the sequence use fluorescent dyes to identify specific bases and DNA sequencesb. Cutting and pasting via recombinant DNA use restriction enzymes to “cut” a gene form one organism and using special enzymes (ligase) “paste” it into the DNA of another organismc. Making copies via polymerase chain reaction (PCR) produces multiple copies of DNA strand

Cell Transformation

1. Transformation process in which bacteria or some other organism takes in DNA from its environment and incorporates it into its own DNA

a. Transforming Bacteria• Plasmids small circular pieces of DNA useful for DNA transfer for 2

reasons:1. Bacterial origin of replication2. Genetic marker a gene that makes it possible to identify the

transformed bacteria Ex: genes for resistance to antibiotics

Cont. Transformation

b. Transforming Plant Cells• Infect plant cells with recombinant plasmid whose

tumor producing gene has been inactivated

c. Transforming Animal Cells• Inject DNA directing into the nucleus of an egg

cell, foreign DNA is inserted into the chromosome

Applications of Genetic Engineering 1. Transgenic Organisms contain genes from other organisms

a. Transgenic Microorganisms– Bacteria transformed with human genes for insulin, growth

hormone, clotting favors etc. produce human products

b. Transgenic Animals

– Mice with human immune systems are used to study effects of disease– Livestock with extra copies of growth hormone to produce faster growth

and less fatty meat

c. Transgenic Plants – Genetically modified food (GM) 52% of soy beans and 25% corn – Plants contain genes that produce natural insecticide or weed resistance

Transgenic Animal: Belgian Blue Cattle

Cloning1. Clone member of a population

of genetically identical cells produced from a single cell

• Steps: 1. Nucleus of egg cell removed

2. Donor nucleus fused with egg cell using an electric shock3. Fused cell begins to divide4. Embryo placed in uterus of foster mother

Dolly’s Bonnie