Chapter 12DNA Technology and

Genomics(aka GENETIC ENGINEERING)

ALIGNED WITH “Ch. 12 DNA Technology and Genomics Questions” Worksheet

1. What makes recombinant DNA technology different from just DNA technology? (12.1)

DNA Technology - method for studying & manipulating genetic material

Recombinant DNA – DNA in which two different sources are combined in vitro into the same DNA molecule

1. What are some examples of recombinant DNA technology? (12.1) Mass production of chemicals (cancer

drugs, pesticides, insulin) Transfer of genes from one organism

to anotherProduction of pest-resistant plants,

heartier crops, more muscular farm animals

Piggies + Jellyfish GeneWhile these glowing pigs may be just “fun,” Asian researchers have created a glowing fish whose luminescence can be used as an indicator of the presence or absence of certain chemical pollutants((http://images.google.com/imgres?imgurl=http://www.damninteresting.com/wpcontent/GlowingPigs.JPG&imgrefurl=http://www.damninteresting.com/%3Fp%3D370&h=256&w=369&sz=67&hl=en&start=3&um=1&tbnid=XO6s7m4UHZqCjM:&tbnh=85&tbnw=122&prev=/images%3Fq%3Dglowing%2Bplants%26svnum%3D10%26um%3D1%26hl%3Den )

2. What are plasmids? What makes them such a good tool in gene cloning? (12.1)

Plasmid – small, circular DNA molecules that replicate separately from the larger bacterial chromosome

Plasmids can carry foreign genes (genes from other organisms) and replicate QUICKLY and CHEAPLY in the lab good for making LOTS of copies of the foreign gene

4. What is genetic engineering and what is its role in biotechnology? (12.1)

Genetic engineering is the direct manipulation of genes for practical purposes (DNA fingerprinting, genetically modified organisms and food, transplantation of genes, cloning)

Biotechnology uses GE to use organisms and their components to make useful products

5. What are restriction enzymes and how do they function in cloning genes? (12.2)

Restriction Enzyme (RE) – molecular scissors which identify and “cut” certain nucleotide sequences, creating restriction fragments. Leave either blunt ends (not useful) or “sticky ends” which can be combined with other sticky ends (see next slide)

In nature, these enzymes protect bacterial cells from “intruder” DNA from bacteriophages (will chop up foreign DNA); bacteria protect their own DNA from RE’s by chemical modification (methylation – adding methyl groups to their A’s and C’s)

Use in gene cloning: Isolate the gene of interest using a restriction enzyme

Cut the donor DNA & plasmid with the same RE to make complimentary sticky ends!!

6. What is meant by the term “sticky ends”? Why are they so important in genetic recombination? (12.2)

Sticky ends are the single stranded ends of double stranded DNA fragments; the unpaired nucleotides can pair with complimentary bases from another molecule cut with the same RE!!!!

Only sticky ends cut with same RE will be complimentary

http://highered.mcgraw-hill.com/olc/dl/120078/bio37.swf

EcoRI – cleaves at AATT

7. Why is it important to cut the two DNA sources with the same restriction enzyme? (12.2)

Sample RE’s and their restriction sites

3. Briefly describe the process of gene cloning. (12.2)

Bacterial plasmid (vector) and gene of interest (already cut by RE) are mixed… complimentary base pairing assures that GOI (gene of interest) gets incorporated into plasmid (step 3)

DNA ligase covalently bonds nucleotide backbone (step 4)

Result is a recombinant plasmid which, when inserted into a bacterial cell, will multiply the new DNA (clone) (steps 5-6)

Note: the plasmid vector usually also contains an antibiotic resistance gene that will allow scientists to isolate colonies that have the GOI. (Will grow bacteria on pates w/antibiotic – those with out the plasmid will be killed, those with plasmid can survive).

8. What is a genomic library? What two types of vectors can be used to create these libraries? (12.4)

When cutting with a RE, you get not only the gene of interest, but all possible fragments resulting from that cut!!

Genomic Library – the entire collection of all the cloned DNA fragments from a genome

Bacterial plasmids and bacteriophages can be used as vectors to create libraries

9. What is cDNA? Explain how reverse transcriptase works to create cDNA. (12.5)

cDNA – DNA that is complimentary to processed mRNA; obtained by REVERSING TRANSCRIPTION from a mRNA sequence (catalyzed by reverse transcriptase)

Single-stranded DNA molecule then creates a compliment using DNA polymerase

10. What is the advantage for using cDNA in the cloning process? (12.5)

The resulting cDNA lacks all the introns…it only has the important genetic information because all the introns were spliced out during RNA processing

Since bacteria can’t remove introns, cDNA is used to clone human genes

Also useful in studying particular cell functions

11. Describe the advantages for using bacteria, yeast, and mammalian cells for mass production of gene products. Give one example and its use for each. (12.6)

BACTERIA Readily available & cheap Have plasmids Grow rapidly Produce large quantities

QUICKLY YEAST

Easy to grow Good at synthesizing eukaryotic

proteins (can remove introns) Have plasmids

MAMMALIAN CELLS Attach sugars correctly to

make glycoproteins Can mass produce gene

product by whole animals rather than cells (sheep produce CF treatment in milk)

12. Briefly describe how DNA technology is being used to create vaccines. (12.7)

Vaccine – a harmless variant or derivative of a pathogen (usually bacteria or virus) that is used to prevent an infectious disease by stimulating an immune response in the vaccine recipient (human)Genetically engineered cells can be used to

produce large amounts of the virus’ outer protein coat (hepatitis B vaccine)

Mutant viruses can be made by altering one or more of the genes; immune response still triggered

Replace some genes in harmless virus to provide immunity to several diseases simultaneously

13. Explain how DNA probes tag a gene. (12.8)

A radioactively labeled complement (the probe) to the gene of interest is created and introduced to single stranded DNA from a phage clone

Can be used to screen an entire bacterial colony to discover which one(s) contain genes of interest