Key concept: DNA sequences oforganisms can be changed.

A clone is a genetically identical copy of a gene or of an organism.

• Some plants clone themselves from their roots.• Bacteria produce identical genetic copies of themselves through binary fission.• Human identical twins are clones of each other.

Scientists swap DNA between cells with a technique called nuclear transfer.

• An unfertilized egg is taken from an animal, and the egg’s nucleus is removed.• The nucleus of a cell from the animal to be cloned is implanted into the egg.• The egg is stimulated and, if successful, the egg will begin dividing.

• After the embryo grows for a few days, it is transplanted into a female.

In 1997 a sheep named Dolly became the first clone of an adult mammal.

The success of Dolly led to the cloning of adult cows, pigs, and mice.

Go to Click and Clone. Complete the Click and Clone worksheet.

• Scientists can use organs from cloned mammals for transplant into humans.

• Cloning could help save endangered species. Cells from endangered species could be taken and used to produce clones that would increase the population of the species.

• High failure rate• The enucleated egg and the transferred nucleus may not be compatible.• An egg with a newly transferred nucleus may not begin to divide or develop properly.• Implantation of the embryo into the surrogate mother might fail.• The pregnancy might fail.

• Problems during later development• “Large Offspring Syndrome”

• Cloned animals tend to be much bigger at birth than their natural counterparts. • Abnormally large organs that can lead to breathing, blood flow, and other problems.

• Some clones without LOS have developed kidney or brain malformations and impaired immune systems, which can cause problems later in life.

• Abnormal gene expression patterns• In a naturally-created embryo, the DNA is programmed to express a certain set of genes. Later on, as the embryonic cells begin to differentiate, the program changes. For every type of differentiated cell (skin, blood, bone, etc.), this program is different.

• In cloning, the transferred nucleus doesn’t have the same program as a natural embryo. It is up to the scientist to reprogram the nucleus.• Complete reprogramming is needed for normal or near-normal development.• Incomplete programming will cause the embryo to develop abnormally or fail.

• Telomeric differences• As cells divide, their chromosomes get shorter. This is because the DNA sequences at both ends of a chromosome, called telomeres, shrink in length every time the DNA is copied.• The older the animal is, the shorter its telomeres will be. This is a natural part of aging.

• When scientists looked at the telomere lengths of cloned animals, they found no clear answers.• Chromosomes from cloned cattle or mice had longer telomeres than normal. These cells showed other signs of youth and seemed to have an extended lifespan compared with cells from a naturally conceived cow.

• On the other hand, Dolly the sheep’s chromosomes had shorter telomere lengths than normal. This means that Dolly’s cells were aging faster than the cells from a normal sheep.• To date, scientists aren’t sure why cloned animals show differences in telomere length.

• Genetic engineering is the changing of an organism’s DNA to give the organism new traits

• Possible because the genetic code is shared by all organisms.• Based on the use of recombinant DNA, which is DNA that contains genes from more than one organism

Benefits of recombinant DNA:• Could be used to produce crop plants that make medicines and vitamins• Scientists are studying ways of using recombinant DNA to make vaccines to protect against HIV

Bacteria are commonly used in genetic engineering.

• Bacteria have tiny rings of DNA called plasmids.• Plasmids are closed loops of DNA that are separate from the bacterial chromosome and that replicate on their own within the cell.

• Recombinant DNA is found naturally in bacteria that take in exogenous DNA, or DNA from a different organism, and add it to their own.• Scientist have adapted what happens in nature to make artificial recombinant DNA.

Steps to making recombinant DNA:• A restriction enzyme is used to cut out the desired gene from a strand of DNA.• Plasmids are cut with the same enzyme.• The plasmid opens, and when the gene is added to the plasmid, their complementary sticky ends are bonded together by a process called ligation.

After a gene is added to a plasmid, the genetically engineered plasmids can be put into bacteria.

• The transformed bacteria make many copies of the new gene.• The bacteria with the recombinant plasmid are called transgenic bacterium.

Crops:• Enhanced taste and quality• Reduced maturation time• Increased nutrients, yields, and stress tolerance • Improved resistance to disease, pests, and herbicides • New products and growing techniques

Animals: • Increased resistance, productivity, hardiness, and feed efficiency• Better yields of meat, eggs, and milk• Improved animal health and diagnostic methods

Environment:• "Friendly" bioherbicides and bioinsecticides • Conservation of soil, water, and energy• Bioprocessing for forestry products• Better natural waste management • More efficient processing

Society:• Increased food security for growing populations

Safety:• Potential human health impacts, including allergens, transfer of antibiotic resistance markers, unknown effects• Potential environmental impacts, including: unintended transfer of transgenes through cross-pollination, unknown effects on other organisms (e.g., soil microbes), and loss of flora and fauna biodiversity

Access and Intellectual Property: • Domination of world food production by a few companies• Increasing dependence on industrialized nations by developing countries •Biopiracy, or foreign exploitation of natural resources

Ethics:• Violation of natural organisms' intrinsic values• Tampering with nature by mixing genes among species • Objections to consuming animal genes in plants and vice versa • Stress for animal

Labeling:• Not mandatory in some countries (e.g., United States) • Mixing GM crops with non-GM products confounds labeling attempts