Bacteria have small rings of DNA in the cytoplasm, called plasmids ( Figure 1.1). A plasmid is not part of the bacterial chromosome, but an additional pieced of DNA. When putting foreign DNA into a bacterium, the plasmids are often used as a vector. Viruses can also be used as vectors. The manipulation of the plasmid DNA, and then the insertion of the recombinant plasmid into a bacterium, is an invaluable tool in scientific research. This image shows a drawing of a plasmid. The plasmid has two large segments and one small segment depicted. The two large segments (green and blue) indicate antibiotic resistances usually used in a screening procedure. The antibiotic resis- tance segments ensure only bacteria with the plasmid will grow. The small segment (red) indicates an origin of replication. The origin of replication is where DNA replication starts, copying the plasmid.
Recombinant DNA is the combination of DNA from two different sources. For example, it is possible to place a human gene into bacterial DNA. Recombinant DNA technology is useful in gene cloning and in identifying the function of a gene. Recombinant DNA technology can also be used to produce useful proteins, such as insulin. To treat diabetes, many people need insulin. Previously, insulin had been taken from animals. Through recombinant DNA technology, bacteria were created that carry the human gene which codes for the production of insulin. These bacteria become tiny factories that produce this protein. Recombinant DNA technology helps create insulin so it can be used by humans. Recombinant DNA technology is used in gene cloning. A clone is an exact genetic copy. Genes are cloned for many reasons, including use in medicine and in agriculture. Below are the steps used to copy, or clone, a gene: 1. A gene or piece of DNA is put in a vector, or carrier molecule, producing a recombinant DNA molecule. 2. The vector is placed into a host cell, such as a bacterium. 3. The gene is copied (or cloned) inside of the bacterium. As the bacterial DNA is copied, so is the vector DNA. As the bacteria divide, the recombinant DNA molecules are divided between the new cells. Over a 12- to 24-hour period, millions of copies of the cloned DNA are made. 4. The cloned DNA can produce a protein (like insulin) that can be used in medicine or in research.
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a clone can be a fairly close genetic copy.
a. true --> b. false
a plasmid is a chromosome from a bacterium.
a. true --> b. false
what is the first step in gene cloning?
a) placing a plasmid into a host cell. b) placing the gene of interest into a host cell. --> c) placing the gene of interest into a vector. d) placing a plasmid into a vector.
which of the following statements is true?
a) cloned genes are used in medicine and agriculture. b) bacteria can easily produce human proteins. c) a vector is replicated inside a bacterial cell. --> d) all of the above statements are true.
what is the origin of replication?
--> a) a spot in the dna sequence of a plasmid that signals the beginning of b) a spot in the dna sequence of a gene that signals the beginning of replication. c) a spot in the dna sequence of a cell that signals the beginning of replication. d) a spot in the dna sequence of a plasmid that signals the beginning of transcription.
what is the purpose of antibiotic resistance segments?
a) the antibiotic resistance segments ensure only bacteria with insulin will grow. b) the antibiotic resistance segments ensure only plasmids with the bacteria will grow. --> c) the antibiotic resistance segments ensure only bacteria with the plasmid will d) the antibiotic resistance segments ensure only plasmids with the insulin will grow.
which best describes a plasmid?
a) a large ring of dna in the cytoplasm of a bacterium. --> b) a small round piece of bacterial dna. c) a small ring of dna in the cytoplasm of many organisms. d) a large extrachromosomal piece of prokaryotic dna.
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