Answer questions #1-5 on Text page 321, Section Assessment.

1. Name two methods used by breeders to increase the rate of mutation.

2. Biologists use _______ to cut the DNA molecules at a specific sequence of nucleotides to make smaller fragments.

3. True or False: The pattern of colored bands on a gel tells the exact sequence of bases in DNA.

Changing the Living World and Manipulating DNA

Allows only those traits that are desirable for a certain organism to pass on to the next generation.• Burbank potato• Hybridization—crossing dissimilar

individuals to get the best of both What is the benefit? Give an example

• Inbreeding—continued breeding of individuals with similar characteristics What are the benefits? What are the risks?

Breeders can increase the genetic variation in a population by inducing mutations, which are the ultimate source of genetic variability.• Can use radiation and chemicals

Bacteria• Millions of organisms at one time, radiation and

chemicals, higher chance of beneficial mutation Plants

• Drugs that cause nondisjunction• Polyploidy

Scientists can use their knowledge of the DNA structure to make unlimited copies of DNA and make changes to the DNA. This process of genetic engineering use the following processes• DNA extraction• Cutting DNA• Separating DNA• Reading the sequence• Cutting and Pasting• Making Copies

Open the cells and separate the DNA from the other cell parts by a simple chemical procedure.

DNA molecules from most organisms are too large to be studied as a whole, so they cut them into precise small fragments using restriction enzymes.• Restriction Enzymes are very precise, and cut

DNA at a specific sequence of nucleotides. • Lock and Key—a particular restriction enzyme

will only cut a DNA sequence if matches precisely.

• EcoR I—Figure 13-5• Leaves “Sticky Ends”—can attract

complementary sequences

Gel Electrophoresis• The cut DNA fragments are poured into

wells on a gel (thick piece of gelatin)• An electric current is passed through the

gelatin—causing the DNA fragments to move toward the opposite end.

• Longer strands move more slowly and do not migrate as far as smaller strands.

• The pattern can be used to compare the gene composition of different organisms or different individuals.

A complementary DNA strand is made using fluorescent nucleotides.

DNA polymerase adds these nucleotides to the DNA fragments in the gel.

When a fluorescent nucleotide is added, replication stops.

The mixture of fragments can then be separated on a gel.

You can then read the sequence on the gel. Each base has a different color.

The order of the colored bands tells the exact sequence of the bases in the DNA

This process is used to change DNA. Short sequences can be assembled

using DNA synthesizers. DNA can then be spliced together.

Synthetic DNA can be combined with an organisms original DNA or you can combine DNA from different organisms

Recombinant DNA—combination of DNA from different sources.

Polymerase Chain Reaction (PCR)• Add primers to each end of the chain you

want to copy (a complementary strand)• Heat DNA to separate the strands (create a

bubble)• DNA polymerase makes copies of the

regions between the strands. • The copies then serve as templates to make

more copies.• A few dozen cycles can produce millions of

copies of DNA.

Read Text 327-329

Be sure DNA Fingerprint Lab is complete

Study Guide 94, 94a and 95