Biology- Chapter 12: "DNA Technology"

Genetically modified whole animals are also used to produce

drugs

The production of GM crops is often more profitable, because the

modifications improve yields. Advocates for GM foods point out that transgenic crops will become increasingly necessary to combat starvation as more food must be grown on less space.

Using the methods of DNA technology, scientists can

modify specific genes and move them between organisms as different as bacteria, plants, and animals.

In the United States, all genetic engineering projects are evaluated for

potential risks by a number of regulatory agencies, including the Food and Drug Administration, Environmental Protection Agency, National Institutes of Health, and Department of Agriculture.

As of 2017, lawyers at the Innocence Project have helped to exonerate more than

350 convicted criminals, including 20 on death row.

In 2005, researchers completed the genome sequence for our closest living relative, the chimpanzee. Comparisons with humans showed that we share

96% of our genome

Advances in genetic profiling raise privacy issues.

In 2014, the U.S. Supreme Court, by a 5-4 vote, upheld the practice of collecting DNA samples from suspects at the time of their arrest (before they had been convicted). Ruling that obtaining DNA is "like fingerprinting and photographing, a legitimate police booking procedure that is reasonable under the Fourth Amendment," the Supreme Court decision will likely usher in an era of expanded use of DNA profiling in many aspects of police work.

Human DNA technology raises legal and ethical questions—few of which have clear answers.

Should we try to eliminate genetic defects in our children and their descendants? Should we interfere with evolution in this way? Genetic variety is a necessary ingredient for the adaptation of a species as environmental conditions change with time. Genes that are damaging under some conditions may be advantageous under others. Are we willing to risk making genetic changes that could be detrimental to our species in the future?

In addition to forensic applications, PCR can be used in the treatment and diagnosis of disease. PCR can be used to

amplify, and thus detect, HIV in blood or tissue samples and diagnose hundreds of human genetic disorders by being used with primers that target the genes associated with these disorders.

An individual's unique DNA sequence, or genetic profile, can be obtained by

analysis of tissue or body fluids

The first targets of genomics research were

bacteria, with relatively little DNA.

Modified strawberry plants produce

bacterial proteins that act as a natural antifreeze, protecting the delicate plants from the damages of cold weather.

Scientists have genetically engineered bacteria to mass-produce a variety of useful chemicals, from

cancer drugs to pesticides, and have transferred genes from bacteria to plants and from one animal species to another.

Growing insect-resistant plants reduces the need for

chemical insecticides.

Scientists construct recombinant DNA by

combining pieces of DNA from two different sources—often from different species—to form a single DNA molecule.

DNA profiling depends upon

comparing lengths of DNA fragments.

Genomics is the study of

complete sets of genes (genomes).

There is also a danger that information about disease-associated genes

could be abused. One issue is the possibility of discrimination and stigmatization. In response, the U.S. Congress passed the Genetic Information Nondiscrimination Act of 2008. Title I of the act prohibits insurance companies from requesting or requiring genetic information during an application for health insurance. Title II provides similar protections in employment.

Governments and regulatory agencies throughout the world are grappling with how to

facilitate the use of biotechnology in agriculture, industry, and medicine while ensuring that new products and procedures are safe.

Recombinant DNA technology is widely used in

genetic engineering, the direct manipulation of genes for practical purposes.

Organisms that have acquired one or more genes by artificial means are called

genetically modified organisms (GMOs).

In the United States today, nearly all of our corn, soybean, and cotton crops are

genetically modified.

As the repository of the genetic information from which all of life's inherited characteristics develop,

genomes hold the key to our genetic identity.

DNA technology can provide evidence of either

guilt or innocence.

Genetically modified bacteria have also been used to produce

human growth hormone (HGH), a protein that helps dissolve blood clots, vaccines, and erythropoietin (EPO), used to treat anemia.

Humulin is

human insulin produced by genetically modified bacteria. In humans, insulin is a protein normally made by the pancreas. Because human insulin is not readily available, diabetes was historically treated using insulin from cows and pigs.

The polymerase chain reaction (PCR)

is a technique by which a specific segment of DNA can be amplified (by targeting and copying it quickly and precisely) and permits a scientist to obtain enough DNA from even minute amounts of blood or other tissue to allow a DNA profile to be constructed.

In forensic cases using STR analysis with the 13 standard markers, the probability of two people having identical DNA profiles is somewhere between

one chance in 10 billion and one in several trillion. Thus, despite problems that can still arise from insufficient data, human error, or flawed evidence, genetic profiles are now accepted as compelling evidence by legal experts and scientists alike.

By transferring the gene for a desired protein into a bacterium, yeast, or other kind of cell that is easy to grow in culture, scientists can

produce large quantities of useful proteins that are present naturally only in small amounts.

Genetic profiles can be used to

provide evidence in criminal and paternity cases and to identify human remains

Bioinformatics can also

provide insights into our evolutionary relationships with nonhuman animals.

By comparing humans with related species both living (chimpanzees) and extinct (Neanderthals), researchers are shedding light on the

recent evolutionary history of our own species and the age-old question of what makes us human.

Genetically modified (GM) foods account for a significant percentage of

several staple crops in the United States, Argentina, and Brazil. Together, these nations account for more than 80% of the world's supply of GM crops.

The genomes of thousands of species have been published and

tens of thousands are in progress.

DNA profiling is

the analysis of DNA samples to determine whether they come from the same individual.

The Human Genome Project was a massive scientific endeavor to determine

the nucleotide sequence of all the DNA in the human genome and identify the location and sequence of every gene. At the end of the project, more than 99% of the genome had been determined to 99.999% accuracy. The biggest surprise from the Human Genome Project is the relatively small number of human genes—currently estimated to be about 21,000.

If the newly acquired gene is from another organism, typically of another species, the recombinant organism is called a

transgenic organism.

As more information becomes available about our personal genetic makeup, some people question

whether greater access to this information is always beneficial. For example, mail-in kits have become available that can tell healthy people their relative risk of developing various diseases later in life. Some argue that such information helps families to prepare. Others worry that the tests prey on our fears without offering any real benefit because certain diseases, such as Parkinson's, are not currently preventable or treatable.

Bacteria are the

workhorses of modern biotechnology. Biologists often manipulate genes in the laboratory using bacterial plasmids, which are small, circular DNA molecules that duplicate separately from the larger bacterial chromosome, can carry virtually any gene and are passed from one generation of bacteria to the next, and are key tools for gene cloning, the production of multiple identical copies of a gene-carrying piece of DNA. DNA cloning methods are central to most genetic engineering tasks.

As soon as scientists realized the power of DNA technology, they began to

worry about dangers such as the creation of hazardous new disease-causing organisms and the transfer of cancer-causing genes into infectious bacteria and viruses. To address such concerns, scientists developed a set of guidelines that have become formal government regulations in the United States and other nations. One example is a set of strict laboratory procedures to protect researchers from infection by engineered microorganisms and to prevent microorganisms from leaving or surviving outside the laboratory.