I) Tools of DNA technology A. PCR (Polymerase Chain Reaction): method of copying DNA sequences 1. DNA is copied in a similar way to natural replication in our cells, but much faster.
2.PCR consists of 25-30 cycles of the following three steps: a.dna is heated up until complementary strands separate (called denaturation). b.as the DNA cools, special nucleic acids called primers attach to the separated DNA strands. Primers are used to target specific sequences for copying. c.dna polymerase starts at the primers and adds complementary nucleotides down the length of the DNA strand. PCR Each cycle doubles the amount of DNA present.
B. Restriction Enzymes: specialized proteins used to cut DNA 1. A restriction enzyme recognizes one specific DNA sequence. 2. When a restriction enzyme encounters the target sequence, it will cut the DNA in that spot only. 3.Many restriction enzymes do not cut straight through both strands, leaving what are called sticky ends as shown below: 4.Sticky ends are very useful to scientists that are interested in moving a gene from one organism into another.
C. Gel Electrophoresis: process of separating DNA fragments using an electric current 1. DNA is negatively charged, therefore it will be attracted to a positive charge. 2. If a DNA sample is placed in a solid, but flexible gel, it can be pulled through by an electrical current. 3.Long fragments of DNA are much more difficult to move through the gel, so they will not travel as far as short fragments. 4.The end result of gel electrophoresis is a separation of DNA fragments based on their size.
II) Biotech in Forensics A. Making a DNA Fingerprint 1.If biological evidence is left at a crime scene (blood, hair, saliva, etc.), detectives can collect it and send it to the lab. The lab needs to copy the DNA using PCR so that they have enough to do their testing. 2. After PCR, the DNA is cut with restriction enzymes. 3. Gel electrophoresis is used to separate the fragments of DNA based on their size.
4.Scientists stain the gel with a chemical that makes DNA glow under UV light, then take a picture of the banding patterns in the gel. This picture is called a DNA fingerprint. Gel electrophoresis Which suspect is probably the attacker? How do you know?
B. Interpreting a DNA fingerprint 1.Each person (except for identical twins) has his or her own unique DNA sequence. 2.Since everyone s DNA sequence differs, if you use the same restriction enzyme on two different people, it may cut the DNA is different places, producing DNA fragments of different lengths. 3.When those DNA fragments are run on a gel, they will produce a unique pattern of bands based on the lengths of the fragments present. 4.If a suspect s DNA fingerprint matches the pattern of the DNA from the crime scene, that is solid evidence to place the suspect at the scene of the crime.
III) Biotech in Medicine A. Genetic Engineering: any deliberate alteration of the genetic material of an organism 1.Recombinant DNA: DNA that results from a gene of one organism being placed into the DNA of another Example: People with diabetes lack the insulin necessary to regulate their blood sugar. In order to get the insulin they need, it was traditionally harvested from cows and/or pigs that were slaughtered for food. This is very expensive and time-consuming.
E. coli is a bacterium that is very easy to grow in the lab. Therefore, researchers have taken the gene for human insulin and have inserted it into E. coli cells, producing bacteria that are able to manufacture insulin very quickly and inexpensively. B. Cloning: process of producing an organism that is an exact genetic copy of the original 1.Most common method of artificial cloning is called Somatic Cell Nuclear Transfer (SCNT) This is how Dolly the sheep was created.
a.an unfertilized egg is removed from a female. b.the nucleus is removed from the egg. c.the nucleus from a somatic cell (diploid body cell=not a gamete) of a donor organism is removed and placed into the now empty egg. d.the egg is chemically or electrically stimulated to divide as if it had just been fertilized. e.the egg is placed into a surrogate mother, who will carry it to term and deliver the clone.
2. Cloning can happen in nature as well (identical twins, fragmentation of a starfish, binary fission in bacteria) C. Stem Cell Research 1.Stem cells are important because they have the ability to differentiate into many different types cells. There are two categories of stem cells: