Download Recombinant DNA - Westwind Alternate School

Recombinant DNA
- DNA from a plant or animal cell is removed and a piece cut out
- That DNA is inserted into the genome of another cell
- once inserted, that DNA will be replicated, transcribed and translated as is the
rest of the organism’s genome
Applications
 to insert human genes into other organism’s genomes that
cause some human traits to be expressed – ex: HGH, insulin
 gene therapy – providing “fixed” genes to people with faulty
genes (must use a vector)
 using genes that naturally fight a disease – ex: p53 into a virus
vector that can be given to patients and may be incorporated
into their genome
 do high tech selective breeding – instead of crossing individuals
with desirable traits hoping for a suitable offspring, take an
offspring and specifically insert genes – resistance to disease,
increased productivity
 biological warfare (insert genes for harmful toxins into harmless
bacteria, transfer to food, infect water/food with bacteria immune
to available antibiotics)
Techniques in Recombinant DNA (photocopied diagram of recombinant DNA
technology)
1. use restriction enzymes to cut the DNA of both organisms to isolate the
gene(s) you want
2. place cut pieces of DNA together with DNA ligase, allow recombination
3. Have(hope) the cells take up the DNA
4. use a selection technique to determine if the DNA has recombined the way
you want it to in a bacterium
One way:
 include a gene for antibiotic resistance beside the gene you really want
 try to grow the bacteria in that medium – only those bacteria that have
incorporated the DNA you want will be able to grow
 clone these bacteria
.
Outline a basic technique used for gene transfer involving:
plasmids = vector = medium by which genes of interest are transferred to host
small (2 - 30 genes) loops of bacterial DNA which bacteria can:
capture from environment by transformation
replicate and transfer to other bacteria
a host cell (bacterium):
receives a gene of interest via a vector (= gene transfer)
replicates repeatedly, passing on gene of interest to offspring (= cloning)
restriction enzymes (endonucleases)
produced naturally by bacteria as defense against viruses
used to cut the desired section of the DNA
recognizes unique sequences of DNA in plasmid and in gene of interest
cuts DNA, producing “sticky ends”
complementary sticky ends in gene of interest and plasmid
allow incorporation of gene of interest into plasmid,
producing recombinant DNA
DNA ligase
creates covalent bonds
joining together gene of interest within plasmid,
producing recombinant DNA
9. State two examples of the current uses of genetically modified crops or animals
genetically modified cows
contain human genes for making medically important proteins (insulin, growth hormone)
human proteins are extracted from cow’s milk and sold as pharmaceuticals
genetically modified tomatoes contain genes to ripen without becoming soft
10. Discuss the potential benefits and possible harmful effects of one example of
genetic modification
Potential escape of genetically engineering plants from cultivation
out-competing naturally occurring varieties, thus becoming super weeds
altering ecosystem interactions
12. Outline a technique for cloning using differentiated cells
-cloning farm animals
-differentiated mammary cells extracted from parent sheep; grown in nutrient-deficient
solution to stop the cell cycle
-undifferentiated egg cells extracted from egg donor; nucleus removed and discarded
-mammary cell placed next to enucleated egg cell
-electric shock causes two cell membranes to fuse, and mitosis to trigger
-mitotic division continues, producing embryo
-embryo implanted into surrogate mother
-after 5-month gestation, Dolly the lamb born with identical genotype to parent donating
nucleus from mammary cell
13. Discuss the ethical issues of cloning in humans
opposition to human cloning is very strong, based on a variety of arguments most of which
invoke a violation of “the sanctity of life”
arguments for human cloning involve at least two different cloning techniques
cloning fetal tissue (stem cells) to produce organs and other tissues (but not entire
individuals) for medical purposes (curing diseases)
cloning individuals
for parents carrying genetic disease alleles, producing normal children has reduced
probability
among embryos produced normally, identify diseased embryos and discard, separate and
clone healthy embryos, saving frozen embryos for later pregnancies