biotech chapter 4
A region on prokaryotic DNA where one or more genes and their controlling elements are located is a(n) .
operon
What are R plasmids?
plasmids that contain genes for antibiotic resistance. These allow resistance to antibiotics to be passed among bacteria.
What are histones? How do these affect regulation of eukaryotic genes?
proteins that bind DNA and condense it into tight coils. DNA that is tightly bound around histones cannot be transcribed because it cannot be accessed by RNA polymerase.
What does it mean when a protein is written with "r" in front of it, eg. rInsulin?
This means that the protein was produced using recombinant DNA
What does it mean for bacteria to be "transformed"?
A bacterium that is transformed has taken up and started expressing foreign DNA (such as from a plasmid transferred to that bacterium.
Describe how gene therapy is used for patients with cystic fibrosis.
A normal, functional version of the gene for CF is added to cells in the nose of CF patients using a virus. This allows the cells to create the protein keeping mucus from building up and clogging the respiratory system.
A DNA molecule has a constant width. This is due to the nitrogenous base pairing. Explain how the nitrogen base pairing maintains the double helix's constant width.
A pairs with T, A has 2 rings but T has 1. G pairs with C, G has 2 rings but C has 1. Because of the relative sizes of the bases that pair together, the double helix keeps a constant width.
List the 4 nitrogenous bases found in the nucleotides of DNA. List 2 ways these bases are similar to or different from each other.
Adenine, Thymine, Guanine and Cytosine. Adenine and guanine are purines-- these have 2 rings, thymine and cytosine are pyrimidines-- these have 1 ring. Guanine and cytosine join with 3 hydrogen bonds, adenine and thymine join with 2 hydrogen bonds.
Explain how a series of genes gets turned on or off in a prokaryotic operon while demonstrating knowledge of the function of the regulatory gene, the promoter, the repressor, the operator, RNA polymerase and the structural genes.
An operon contains a promoter, the region where RNA polymerase binds to begin transcription. The operator, located just before the structural genes (which produce the mRNA to translate into protein products) can bind a repressor. When the repressor is bound to the operator, the structural genes cannot be transcribed by RNA polymerase. The repressor is coded for by genes called regulatory genes. This allows prokaryotes to turn genes on or off depending if the product of the structural genes is needed.
How is the order of amino acids in a protein determined?
By the order of the DNA bases which give the code.
Explain how DNA molecules vary from one species to another.
Different numbers of chromosomes, different number of base pairs, different genes and locations of genes
How is the packaging of DNA different in eukaryotes and prokaryotes?
Eukaryotes have multiple linear chromosomes wrapped up around histones, prokaryotes have single circular chromosomes
What type of bond holds nitrogen bases to each other in a nucleic acid?
Hydrogen bonds
Explain how the regulation of eukaryotic genes is different from prokaryotic genes-- use the terms promoter, enhancer, silencer, transcription factors, intron, and exon.
In eukaryotic DNA, RNA polymerase binds to the promoter region just as it does in prokaryotic DNA. However, in eukaryotic DNA there are silencer or enhancer regions that may be very far from the genes to be transcribed. These regions bind transcription factors which are molecules that may increase or decrease the rate of transcription of the structural genes. After the structural genes are transcribed into mRNA, sections of the mRNA may be removed- these are called introns. Exons are the sections of DNA that are expressed (code for the completed amino acid sequence). After introns are removed, exons remain and form the functional mRNA which will be translated into a protein at the ribosome. Different forms of a protein may be made by removing some introns and leaving others.
What is recombinant DNA?
Recombinant DNA is DNA that has been modified.
What is "site-specific mutagenesis?"
Site-specific mutagenesis is a technique for changing sections of DNA code. This involves exposing the DNA to mutagens (such as UV light, radiation, chemicals) in order to produce a change in the DNA. The changes caused by mutagens are random, and may cause unexpected outcomes while looking for a particular result.
If a piece of one strand of a DNA molecule has the following sequence on it, what would be the nitrogen base sequence on the opposite DNA strand? ATG CCC GTG TTA AAA TGT GGG
TAC GGG CAC AAT TTT ACA CCC
A sample contains three DNA fragments with sizes of 3000, 20,000, and 80,000bp. The sample is loaded onto a gel and run, what will the samples look like on the gel? Sketch or explain the movement of the fragments.
The fragment that is 3000 base pairs will travel the furthest in the gel because it is shortest. The fragment that is 20,000 base pairs will travel the next furthest and the fragment that is 80,000 base pairs will travel the shortest distance from where the DNA is loaded.
How can a virus be used as a vector?
Viruses may be used as vectors because their DNA is relatively short and easy to manipulate and viruses can infect cells, so viral DNA can be modified to include the target gene and then the virus can insert the DNA in the host cell. A virus must be chosen that is not pathogenic (does not cause disease) and can infect the target cell.
What is a vector? Explain how plasmids can be used as vectors.
a piece of DNA that carries genes into a cell. Plasmids can be used as vectors because a gene can be spliced into a plasmid and then the plasmid can be taken up from the environment into a bacterial cell.
Explain what a plasmid is.
a small extra ring of DNA in prokaryotic cells
Where is DNA found in a prokaryotic cell?
cytoplasm