The resulting DNA, because it is made up of long polymers, forms a gelatinous mass. RNA is studied to understand gene expression patterns in cells. Some are even secreted by our own skin and are very difficult to inactivate. Because nucleic acids are negatively charged ions at neutral or alkaline pH in an aqueous environment, they can be moved by an electric field.
Gel electrophoresis is a technique used to separate charged molecules on the basis of size and charge. The nucleic acids can be separated as whole chromosomes or as fragments. The nucleic acids are loaded into a slot at one end of a gel matrix, an electric current is applied, and negatively charged molecules are pulled toward the opposite end of the gel the end with the positive electrode. Smaller molecules move through the pores in the gel faster than larger molecules; this difference in the rate of migration separates the fragments on the basis of size.
The nucleic acids in a gel matrix are invisible until they are stained with a compound that allows them to be seen, such as a dye. Distinct fragments of nucleic acids appear as bands at specific distances from the top of the gel the negative electrode end that are based on their size Figure A mixture of many fragments of varying sizes appear as a long smear, whereas uncut genomic DNA is usually too large to run through the gel and forms a single large band at the top of the gel.
DNA analysis often requires focusing on one or more specific regions of the genome. It also frequently involves situations in which only one or a few copies of a DNA molecule are available for further analysis. These amounts are insufficient for most procedures, such as gel electrophoresis. Polymerase chain reaction PCR is a technique used to rapidly increase the number of copies of specific regions of DNA for further analyses Figure PCR is used for many purposes in laboratories.
These include: In general, cloning means the creation of a perfect replica. Typically, the word is used to describe the creation of a genetically identical copy. Cloning allows for the creation of multiple copies of genes, expression of genes, and study of specific genes. To get the DNA fragment into a bacterial cell in a form that will be copied or expressed, the fragment is first inserted into a plasmid.
A plasmid also called a vector in this context is a small circular DNA molecule that replicates independently of the chromosomal DNA in bacteria.
- Isolation of Nucleic Acids.
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Modified plasmids are usually reintroduced into a bacterial host for replication. As the bacteria divide, they copy their own DNA including the plasmids. Plasmids occur naturally in bacterial populations such as Escherichia coli and have genes that can contribute favorable traits to the organism, such as antibiotic resistance the ability to be unaffected by antibiotics.
Plasmids have been highly engineered as vectors for molecular cloning and for the subsequent large-scale production of important molecules, such as insulin. A valuable characteristic of plasmid vectors is the ease with which a foreign DNA fragment can be introduced. These plasmid vectors contain many short DNA sequences that can be cut with different commonly available restriction enzymes. Restriction enzymes also called restriction endonucleases recognize specific DNA sequences and cut them in a predictable manner; they are naturally produced by bacteria as a defense mechanism against foreign DNA.
Many restriction enzymes make staggered cuts in the two strands of DNA, such that the cut ends have a 2- to 4-nucleotide single-stranded overhang. The sequence that is recognized by the restriction enzyme is a four- to eight-nucleotide sequence that is a palindrome. Like with a word palindrome, this means the sequence reads the same forward and backward. In most cases, the sequence reads the same forward on one strand and backward on the complementary strand. When a staggered cut is made in a sequence like this, the overhangs are complementary Figure In this way, any DNA fragment can be spliced between the two ends of a plasmid DNA that has been cut with the same restriction enzyme Figure Plasmids with foreign DNA inserted into them are called recombinant DNA molecules because they contain new combinations of genetic material.
Proteins that are produced from recombinant DNA molecules are called recombinant proteins. Not all recombinant plasmids are capable of expressing genes. Gene Technologies in Our Lives Read the passage below. Then answer the questions that follow. In , a scientist captured worldwide attention when he announced the first successful cloning using an adult animal.
A lamb named Dolly was cloned from the nucleus of a mammary udder cell taken from an adult sheep. The clone was made using a process known as somatic-cell nuclear transfer SCNT. SCNT is a process in which the nucleus of an egg cell is replaced with the nucleus of an adult cell.
An electric shock was used to fuse a mammary cell from one sheep with an egg cell without a nucleus from a different sheep. The fused cell divided to form an embryo, which was implanted into a surrogate mother. Dolly was born soon after. She was genetically identical to the adult sheep from which the mammary cell was taken.
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What occurred in ? Why is the word udder enclosed in parentheses in the second sentence? What is somatic-cell nuclear transfer SCNT? Additions and changes to the original content are the responsibility of the instructor.
ch 11 packet
Determine the order in which the steps took place. Write the number of each step in the space provided. Add to collection s Add to saved. Human Genome Project DNA fingerprint Section 3 Section 3 Genetic Engineering Read the passage below. Then answer the questions that follow. Genetic engineering experiments use different approaches, but most share four basic steps. Step 1: Cutting DNA. The DNA is cut into pieces by restriction enzymes. Restriction enzymes are bacterial enzymes that recognize and bind to specific short sequences of DNA and then cut the DNA between specific nucleotides within the sequences.
A vector is an agent that is used to carry the gene of interest into another cell. Commonly used vectors include viruses, yeast, and plasmids.
Review of Nucleic Acid Structure
Plasmids are circular DNA molecules that can replicate independently of the main chromosome of the bacteria. Plasmids are usually found in bacteria. Step 2: Making Recombinant DNA. The DNA fragments from the organism containing the gene of interest are combined with the DNA fragments from the vector. Step 3: In a process called gene cloning, many copies of the gene of interest are made each time the host cell reproduces.
Since bacteria reproduce by binary fission, when a bacterial cell replicates its DNA, it also replicates its plasmid DNA. Step 4: Cells that have received the particular gene of interest are distinguished from the cells that did not take up the vector with the gene of interest. Each time the cells reproduce, they make a copy of the gene of interest. The cells can transcribe and translate the gene to make the protein coded for in the gene.
What are restriction enzymes? What is a vector? All rights reserved. How are vectors and plasmids related?
10.1 Cloning and Genetic Engineering
What is the function of DNA ligase in genetic engineering? What is the product of gene cloning? How does the reproductive method of bacteria ensure the replication of plasmid DNA? In the space provided, write the letter of the term or phrase that best completes the statement. DNA ligase. Genetic Engineering Complete each statement by underlining the correct term or phrase in the brackets.
Study the following steps in a genetic engineering experiment. Determine the order in which the steps take place. Write the number of each step in the space provided. The recombined vectors are returned to the host cell. The host cell reproduces.
Cloning and Genetic Engineering – Concepts of Biology-1st Canadian Edition
DNA from the organism containing the gene of interest and the DNA from the vector are cut into pieces using restriction enzymes. Cells that have received the gene of interest are identified. In a Southern blot, the DNA from each bacterial colony is isolated and cut into fragments by DNA fragments are charged. The larger a DNA fragment becomes, the distance it travels in a gel. After the DNA bands are separated, they are transferred to a piece of filter paper, which is moistened with a n solution.
Human Applications of Genetic Engineering Read the passage below. Many viral diseases, such as smallpox and polio, cannot be treated effectively by existing drugs. Instead they are combated by prevention, using vaccines. A vaccine is a solution containing a harmless version of a pathogen disease-causing microorganism.
In the future, if the same pathogen enters the body, the antibodies are there to combat the pathogen and stop its growth before it can cause disease. Traditionally, vaccines have been prepared either by killing a specific pathogenic microbe or by making the microbe unable to grow. This ensures that the vaccine itself will not cause the disease. The problem with this approach is that there is a small but real danger that a failure in the process to kill or weaken the pathogen will result in transmission of the disease to the very patients seeking protection.
This danger is one of the reasons why rabies vaccines are administered only when a person has actually been bitten by an animal suspected of carrying rabies. What two viral diseases are identified in the first sentence of the passage? What is a vaccine?