Start-up for Wednesday, January 5, 2011

Answer the following questions:

1. Identify and compare the two types of selective breeding.

2. Relate genetic variation and mutations to each other.

3. What is polyploidy?

4. Suggest plant characteristics that could be altered to improve the world’s food supply.

1. Inbreeding is mating the same species and hybridization mates different species.

2. Mutations are the ultimate source of genetic variation.3. Polyploidy is many sets of chromosomes used in plant

production.4. More food, heat/drought tolerance, disease resistance, stronger

stem.

Chapter 13-2 – pages 322-326 KEY CONCEPT How do scientists make changes to DNA?

Objectives: Students will A)Define genetic engineeringB) List five tools genetic engineers use to manipulate DNAC) Summarize how each tool is used

Scientists use several techniques to manipulate DNA.

• Chemicals, computers, and bacteria are used to work with DNA.

• Scientists use these tools in genetics, research and biotechnology = all part of genetic engineering

Obj. A) Define genetic engineering

• Obj. B) List five tools genetic engineers use to manipulate DNA

1. DNA Extraction = removal from cells2. Restriction Enzymes3. Gel Electrophoresis4. DNA Sequencing 5. Polymerase Chain Reaction (PCR)6. Cutting and Pasting – Recombinant DNA

Restriction enzymes cut DNA. = Tool #1

• Restriction enzymes act as “molecular scissors.” – come from various types of bacteria– allow scientists to more easily study and manipulate

genes– cut DNA at a specific nucleotide sequence called a

restriction site

Obj. C) Summarize how each tool is used

• Different restriction enzymes cut DNA in different ways.

– each enzyme has a different restriction site

Obj. C) Summarize how each tool is used

– some cut straight across and leave “blunt ends”

– some make staggered cuts and leave “sticky ends”

Obj. C) Summarize how each tool is used

Restriction maps show the lengths of DNA fragments.

• Gel electrophoresis (Tool #2) is used to separate DNA fragments by size.– A DNA sample is cut

with restriction enzymes.

– Electrical current pulls DNA fragments through a gel.

Obj. C) Summarize how each tool is used

Gel Electrophoresis Continued Of what is this a picture?What is its electrical charge?

Obj. C) Summarize how each tool is used

DNANegative

Make up the gel which the DNA will be put into

Obj. C) Summarize how each tool is used

This is the gel in the liquid state.

Obj. C) Summarize how each tool is used

This is placed in the gel to create wells (holes) to place the DNA.

Obj. C) Summarize how each tool is used

9.1 Manipulating DNAThis is the gel after it has set with the wells created.

Dye added to the DNA

Obj. C) Summarize how each tool is used

Buffer solution is added to the tank to assist with the flow of electric current. Don’t forget DNA has a – charge. Which charge will it travel towards?

Obj. C) Summarize how each tool is used

DNA samples loaded into wells

Obj. C) Summarize how each tool is used

Electrical current applied to the chamber

Obj. C) Summarize how each tool is used

DNA is stained using ethidium bromide

Obj. C) Summarize how each tool is used

– Smaller fragments move faster and travel farther than larger fragments.

– Fragments of different sizes appear as bands on the gel.

– Which two strands contain the smallest DNA fragments?

Obj. C) Summarize how each tool is used

• A restriction map shows the lengths of DNA fragments between restriction sites.

– only indicate size, not DNA sequence

– useful in genetic engineering

– used to study mutations

Obj. C) Summarize how each tool is used

Sequencing DNA – Tool #3

• Shows the order of DNA nucleotides = used in forensics to definitively identify criminals

• Every person has their own unique order of nucleotides• Single stranded DNA is put in test tubes with DNA

polymerase• Nucleotides are added• one nucleotide is tagged with a fluorescent dye• When that nucleotide is added, DNA strand is terminated• Fragments are put in a gel, and the order can be read by

looking at the colored tags.

Obj. C) Summarize how each tool is used

13.1 Ecologists Study Relationships

Fluorescent dye

Single strand of DNA

Strand broken after A

Strand broken after C

Strand broken after G

Strand broken after T

Power source

Gel

Section 13-2

Figure 13-7 DNA Sequencing

Go to Section:

Obj. C) Summarize how each tool is used

PCR – Polymerase Chain Reaction = Tool #4

• Replicates (copies) DNA in a test tube

• Allows a tiny sample of DNA to be “amplified” - millions of new identical copies are produced

• Allows Biologists to study genes

Obj. C) Summarize how each tool is used

TOOL #5 = Cutting and Pasting = Recombinant DNA

• Plasmids are Circular pieces of DNA inside bacteria

• Easily transferred between bacteria allowing for genetic diversity

• Restriction Enzymes splice open plasmids and allow insertion of new genes from other sources.

• Genetic markers – used to ID successful recombination

THE DNA IS RECOMBINED

Obj. C) Summarize how each tool is used

EXIT TICKET

• On a small piece of paper, write down at least three out of the five tools discussed today in manipulating DNA.

• Which tool is used to make new DNA from two different sources?

• Which tool allows scientists to copy DNA?• Which tool separates DNA but its fragment size?