GENE TECHNOLOGIES

Human Genome Project

In 1990 the Human Genome Project began. A genome refers to all of the genetic material in an organism. The Human Genome Project had the goal of determining the entire nucleotide sequence of the human genome by identifying each DNA base pair found in every chromosome. This project was an international effort consisting of more than 20 laboratories in six countries to sequence the 3.2 billion DNA base pairs that make up the human genome. Some of the surprising findings include:

· Humans have only about 25,000 genes when it was expected that we have around 120,000.

· Most human DNA is noncoding, or introns. It appears less than 2% of the human DNA actually codes for proteins.

· Many of the human genes are identical to those of other species.

· All humans are genetically close. The DNA of any two humans is 99.9% similar.

In 2001 the first draft of the human genome was released. In 2003, it was announced that the human DNA sequencing was finished. Knowing the human genome helps researchers diagnose genetic diseases, possibly treat some genetic diseases, and helps to identify individuals.

Introduction: Genomes

Chromosomes, Genes, and DNA

Genetic Engineering

Understanding the human genome now allows the opportunity to locate genes, copy specific genes, turn genes on or off, and even move genes between cells. Genetic Engineering is the alteration of the genetic material of an organism as in transferring genes from one organism to another. For example, some diabetic patients need insulin. Because scientists now know the location of the insulin gene, they were able to remove a normal functioning insulin gene and place it into a bacterial cell. The genetically engineered bacterial cell will now produce human insulin, which can be given to some diabetic patients. Before the production of genetically engineered insulin, which began in 1982, diabetics had to rely on cow or pig insulin which could create adverse reactions. The insulin produced by the bacteria through genetic engineering is from an actual insulin-producing human gene. See the section “Gene Recombination” below for what this process involves.

The DNA that has been manipulated, or recombined, by way of genetic engineering is called recombinant DNA. The organisms with recombinant DNA may be called recombinant, transgenic, or genetically modified, but most often they are referred to as Genetically Modified Organism (GMO).

GMO Uses

Genetic engineering is involved in almost every part of our lives, from food to healthcare. This technology, as with other technologies, has ethical concerns and is highly controversial. We discussed earlier in this course what ethics involves. As with most technologies, many people feel genetic engineering may be stepping out of bounds into areas we shouldn’t enter into, while others feel this is progress which will safely improve all human lives. GMOs can be found in many different areas. GMOs can be used as food crops. Most corn and soybean products sold have been genetically engineered. A gene from Bacillus thuringiensis (bacteria species) that naturally produces an insecticide has been added to these crops as a natural insecticide produced now by the plant. Many other food crops have been engineered to be easier to grow or more nutritious. GMOs can be used in livestock. Many animals are being engineered to grow faster with less fat. GMOs are being used in medical treatment by using bacteria to produce human insulin, as was already mentioned, and other proteins for humans. GMOs can also be used as research tools. Using GMOs can help researchers trace a less noticeable gene. Researchers may place a “glow” gene in an organism that can be used to trace that organism which actually has a less noticeable gene that they wish to study.

Gene Recombination

Gene recombination is the process of inserting a gene of one organism (ex. human insulin gene) into the DNA of another organism (ex. plasmid of bacterial cell). The gene that is inserted will be transcribed and translated as part of the host organism’s DNA, and also replicated easily as the host organism’s DNA replicates. Gene recombination is completed in the following steps:

1. Isolate a gene - The two sets of DNA are cut or opened by the same restriction enzymes so both fragments of DNA will have the same matching “sticky” ends. One fragment of DNA is the desired gene (human insulin gene) to be recombined and utilized. The other DNA (bacterial plasmid) will be used to carry the gene between cells and is called a vector.

2. Producing Recombinant DNA - The DNA fragment from the first organism (human insulin gene – “Donor Gene”) is combined with the host DNA (bacterial plasmid – “Vector”). DNA ligase is then added to help bond the sticky ends of the DNA fragments together.

3. Inserting Recombinant DNA - The recombinant DNA (human insulin gene and bacterial plasmid vector) is inserted into a bacterial cell (GMO – “host”).

4. Cloning DNA - Every time the bacterial cell divides, the recombinant DNA now replicates and divides with each new daughter cell. Each new daughter cell also produces human insulin.

Polymerase Chain Reaction

Polymerase Chain Reaction (PCR) is a technique that is used to make many copies of selected segments of DNA. Adding DNA polymerase, nucleotides, and primers, and controlling the temperature will produce many copies of a DNA sample in a relatively short amount of time. This technique involves separating the two strands of DNA at a high temperature. Next the temperature is lowered and DNA polymerase will replicate the targeted DNA. Sometimes only a very small amount of DNA is available. Scientists will use PCR to quickly produce large amounts of that small DNA sample. Large quantities of copied DNA may be used in identifying people involved in crime scenes, diagnosing genetic disorders, or studying ancient DNA fragments.

DNA Fingerprinting

DNA Fingerprinting (Southern Blot Test) uses a technique known as Gel Electrophoresis which is a technique used to separate fragments of DNA according to their size and charge. DNA Fingerprinting is completed in the following steps:

1. DNA fragment samples for comparison are placed in wells found on one side of the gel.

2. An electric current is passed through the gel from the negatively charged end where the DNA samples are located to the positively charged end of the gel. The DNA fragments migrate across the gel, but not at the same rate. The smaller fragments of DNA travel faster and farther than the larger fragments.

3. Now the bands of DNA that have been separated need to be made visible. The separated bands of DNA are blotted onto filter paper. Probes (radioactive segments of DNA) are added to the filter paper. The probes make the bands of DNA now visible when exposed to photographic film. The bands can now be analyzed for identification of samples through comparing the patterns.

DNA Sequencing

DNA Sequencing (Using the Sanger Method) is the process of determining the exact order of every nucleotide in a gene. This technique uses single-stranded DNA, primers, DNA polymerases, and replication terminators. The fragments produced by the replication terminators (a terminator for each nitrogenous base) will then undergo gel electrophoresis which will separate the fragments into a nucleotide sequence. Each of the four nitrogenous bases (adenine (A), cytosine (C), guanine (G), thymine (T)) is represented by a lane in the gel.

Reading DNA Fingerprinting & DNA Sequencing

Reading “DNA fingerprinting” is done simply through comparing multiple bands and discovering which bands or lanes are most similar to each other. Finding similarities can help identify individuals or find relationships. [Notice that Suspect 2 matches the crime scene DNA.]

Reading the “DNA sequence” requires you to start at the top of the gel and read each band, in order, from top to bottom recording the lane of the band. [Follow the red line of the figure on the right.]

Cloning

A clone is an organism, cell, or piece of genetic material that is genetically identical to one that was pre-existing. The process of making a clone is naturally accomplished in any organism that reproduces asexually. Remember, asexual reproduction creates offspring that are genetically identical to the parent. Producing clones in large animals is a difficult process primarily because of the developmental process and all the chemicals that act as signals. A clone made from an adult mammal was born in 1997 and was named Dolly. Dolly was a cloned sheep. You need to understand that there were 246 failed attempts before Dolly was born. Sometimes clones do not survive for long, sometimes fetuses grow beyond normal size, or sometimes clones fail to develop with normal age. Because of the problems associated with cloning and the ethical dilemmas it creates, human cloning is illegal in many countries.

The cloning of Dolly used a process known as Somatic-Cell Nuclear Transfer (SCNT). This process involves the nucleus of an egg cell being replaced with the nucleus of an adult somatic cell. Then, the egg cell begins to develop as a result of some environmental condition or stimulus. Something to know about the process is that as Dolly grew older, her chromosomes began showing signs of premature aging, because her chromosomes were the age of the donor.

Interactive Activity

The method by which Dolly the sheep was cloned is presented as well as the ethical considerations of human cloning in the following video.

https://www.dnalc.org/view/16992-Cloning-101.html

Stem Cells

A stem cell is a cell that can continuously divide and differentiate into specialized cells. There are three types of stem cells. Totipotent cells can give rise to any cell or tissue type. Pluripotent cells can give rise to all types of cells except germ cells. Multipotent cells can give rise to just a few other cell types. The state of the cell depends on the stage of development of the body and the tissue of which the cell is part. The cells of new embryos are totipotent at first and pluripotent during development. The bone marrow cells of an adult, as well as some other tissue types, are multipotent cells. The issue with stem cell research is the use of extra human embryos from fertility clinics. In some cases, the parents who utilize the fertility clinic will give permission for the scientists to use any extra embryos for research. Using human embryos for the sole purpose of obtaining the stem cells for use in another organism has created a strong ethical debate. A newer source of embryonic stem cells is through SCNT cloning. Some believe this process should be considered ethically acceptable because the embryo produced does not have true parents.

Unit 19 Worksheet Gene Technologies

UNIT VOCABULARY REVIEW

Click on the Quizlet icon below to access the quizlet.com vocabulary flash cards. Review the vocabulary before completing your assessment.

Now answer questions 1 through 20.