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CHAPTER THREE – text review questions
1. Explain the use of an antibiotic (e.g., ampicillin) resistance gene on a vector.
Answer: The antibiotic resistance gene is found on the vector (also known as the
plasmid). This gene confers resistance to the recombinant DNA plasmid when
transformed into bacterial cells and plated on agar media containing the antibiotic,
such as ampicillin. Only bacterial cells that have taken up the vector can grow on
media containing ampicillin, thus allowing for selection of colonies that have taken
up the vector.
2. Describe two advantages for cloning a gene from a cDNA library versus a
genomic DNA library.
Answer: A cDNA library is free of introns and it is enriched for the gene of interest
because it is made from mRNA from the desired tissue type. In contrast, a genomic
DNA library still has introns and it has every gene in the genome, making it more
difficult to find the gene of interest.
3. Describe three reagents used and the three steps in the process of polymerase
chain reaction.
Answer: The reaction calls for Taq polymerase, a pool of nucleotides, primers, and
a thermo cycler. The three steps in the process are as follows: denaturation, which
occurs at 94ºC to separate the DNA strand; annealing, in which the temperature
varies depending on the primers but is usually between 50ºC and 60ºC and allows
the primers to adhere to the DNA strands; and extension, which occurs at 72ºC,
allowing for elongation of the DNA from the primer.
4. Explain the meaning and utility of RNA interference.
Answer: RNA interference (RNAi) is a process within living cells that moderates
the activity of their genes.
5. Explain the dideoxy sequencing method.
Answer: see text pp77-78; using ddNTP (dideoxynucleotide) and read with
autoradiography. Now computer-automated sequencing approaches and nextgeneration sequencing technologies are used.
6. Describe several findings of the Human Genome Project.
The human genome consists of approximately 3.1 billion base pairs. The genome is
approximately 99.9% the same between individuals of all nationalities and
backgrounds. Less than 2% of the human genome codes for genes. The vast
majority of our DNA is non-protein coding. The genome contains approximately
20,000 to 25,000 protein-coding genes. Many human genes are capable of making
more than one protein. Chromosome 1 contains the highest number of genes. The
Y chromosome contains the fewest.
7. Modern biology is experiencing an “-omics” revolution. What does this
mean? Give examples!
Answer: The “omics” revolution of modern biology refers to the rapid expansion of
new disciplines of research that have resulted from genomics studies, as reflected
by new terms using the suffix omics or ome. Generally such studies involve a largescale comprehensive analysis. For example, proteomics involves the study of all
the proteins in a cell or tissue; metabolomics involves the study of all the proteins
and metabolic products involved in a metabolic process, such as carbohydrate
(sugar) metabolism.
8. A. What is PCR? B. If you performed a PCR experiment starting with only
one copy of a double-stranded DNA, approximately how many copies would
be produced by 15 cycles of amplification?
Answer:
A. Laboratory techniques for amplifying and cloning DNA; involves multiple
cycles of denaturation, primer hybridization, and DNA polymerase synthesis of new
strands.
B. Approximately 32,768 (2n-1, where n = number of cycles)