Chapter 20 Questions Flashcards
Gene cloning is crucial to any application involving one gene because _____.
- naturally occurring DNA molecules are very long and contain many genes
- it provides a means to produce large quantities of its protein product
- genes occupy only a small proportion of the chromosomal DNA in eukaryotes, the rest being noncoding nucleotide sequences
- it provides a means to produce many copies of a gene in short period of time
What is an advantage to using a bacterial artificial chromosome (BAC) for generating a genomic library compared to a plasmid or phage that has historically been used for this process?
- BACs carry DNA fragments much larger than plasmids or phages and greatly minimize the number of clones needed to make up the genomic library.
- The use of BACs reduces the frequency with which specific genes will be cut within the coding region by restriction enzymes and divided up among two or more clones.
In which of the following would it be advantageous to create and work with a cDNA (complementary DNA) library rather than a genomic library?
a study of a protein involved in eye development of a salamander and the regulation of the gene that expresses it
The expression of the PAX-6 gene when vertebrate and fruit fly versions of the gene are exchanged between these animal groups illustrates _____.
the common ancestry in the evolution of these animal groups
Which of the following enzymes is key to the automation of PCR (polymerase chain reactions)?
Taq polymerase
Bacteria use restriction enzymes to _____.
destroy foreign DNA
An enzyme that cuts DNA at a symmetrical sequence of bases is called _____.
a restriction enzyme
When a typical restriction enzyme cuts a DNA molecule, the cuts are staggered so that the DNA fragments have single-stranded ends. This is important in recombinant DNA work because _____.
the fragments will bond to other fragments with complementary single-stranded ends
In genetic engineering, “sticky end” refers to _____.
short bits of single-stranded DNA left at the end of DNA molecules cut by restriction enzymes
Which of the following enzymes could seal a nick in one strand of a double-stranded DNA molecule by creating a sugar-phosphate bond between the adjacent, unjoined nucleotides?
DNA ligase
-DNA ligase is a fundamental tool in recombinant DNA technology.
To create recombinant DNA with long-term stability, it is necessary to have which of the following in the test tube?
DNA ligase
What two enzymes are needed to produce recombinant DNA?
a restriction enzyme and a ligase
In recombinant methods, the term “vector” refers to _____.
a plasmid or other agent used to transfer DNA into a living cell
Which arrangement of the following four enzymes represents the order in which they would be used in a typical gene-cloning experiment resulting in the insertion of a cDNA into a bacterial plasmid? Begin with the gene’s mRNA transcript.
reverse transcriptase, DNA polymerase, restriction enzyme, DNA ligase
A scientist wishing to create an organism capable of breaking down several kinds of toxic waste combines genes from several species of bacteria to create a single “superbacterium.” Which of the following would be needed to do this?
- nucleic acid probes
- DNA ligase
- plasmids
- restriction enzymes
A nucleic acid probe is used to _____.
identify genes that have been inserted into bacterial plasmids or separated by electrophoresis
What is the source of the reverse transcriptase used in recombinant DNA technology?
retroviruses
Because eukaryotic genes contain introns, they cannot be translated by bacteria, which lack RNA-splicing machinery. But if you want to engineer a bacterium to produce a eukaryotic protein, you can synthesize a gene without introns. A good way to do this is to _____.
work backward from mRNA to make a version of the gene without introns
DNA synthesized using an RNA template is called _____.
cDNA
In the polymerase chain reaction (PCR), the sequence of bases in the primers is important because it _____.
determines which segment of the genome will be amplified
-PCR starts with double-stranded DNA that is to be copied. Primers, necessary for DNA polymerase to initiate DNA synthesis, are added to the mixture. They are complementary to the ends of the targeted DNA and determine the segment of DNA to be amplified.
A molecular biologist has isolated a short segment of DNA that she wants to replicate in vitro. First she heats the DNA, which separates the two strands, and then she adds _____.
nucleotides, primers, and polymerase
-PCR requires a pool of nucleotide building blocks, primers to initiate DNA synthesis, and polymerase to continue elongation of the new strands.
In the polymerase chain reaction (PCR) technique, a heating phase and a cooling phase alternate. An original sample of DNA would have to pass through how many total rounds of heating and cooling before a sample is increased eight times in quantity?
three
Single nucleotide polymorphisms (SNPs) _____.
- are single base-pair variations in the genomes of the human population
- are genetic markers used to study the genetic basis for disease
- are small nucleotide differences among individuals located in coding and non-coding sequences in the genome
- can be the molecular basis for different alleles
Separating DNA fragments by gel electrophoresis is useful for which of the following?
- identifying DNA fragments for RFLP analysis
- purifying specific DNA fragments
- distinguishing between different alleles of a gene
- identifying a plasmid or a virus by examining its restriction fragment pattern
Southern blotting is _____.
a technique used to study RFLPs
Which of the following is the first step of the Southern blotting procedure?
digesting the DNA with a restriction enzyme
The dideoxyribonucleotide chain-termination method _____.
produces a ladder of DNA fragments, with each individual band labeled with one of four different fluorescent tags
-Each band differs in size by a single nucleotide, and the particular fluorescent tag of the band indicates the identity of the final nucleotide.
The term “RFLP” stands for _____.
restriction fragment length polymorphism
-RFLPs, or restriction fragment length polymorphisms, are small differences in homologous DNA sequences that result in different restriction fragment patterns.
RFLPs have been tremendously useful for genomic mapping studies because _____.
they are not restricted to genes, and are abundantly scattered throughout the genome
The efficiency of cloning, and the ability to generate healthy cloned animals, has been largely hampered by the difficulty of _____.
completely reversing epigenetic alterations in donor cell nuclei such as DNA methylation and chromatin packing
-It is thought that the subtle abnormalities that often affect cloned animals result from an inability to completely reverse these alterations.
“Therapeutic cloning” refers to _____.
the use of cloned embryos as a source of stem cells that could be used to treat disease
-Such cells could potentially be used to treat diseases such as Parkinson’s disease, Huntington’s disease, and diabetes. Nevertheless, the prospect of therapeutic cloning remains quite controversial.
Nuclear transplantation involves _____.
removing the nucleus of an egg cell and replacing it with the nucleus of a somatic cell
_____ can give rise to any type of cell whereas _____ can give rise to a subset of cell types.
Embryonic stem cells … adult stem cells
During the process of differentiation, cells _____.
express different genes in response to cell signaling
Dolly, the sheep, was cloned from an adult cell. She had a number of health problems and died at a relatively young age. Three mules that were born in 2003 were cloned from fetal cells. If it turns out that the mules remain healthy and live normal lives, how would this outcome tie in with Gurdon’s observations with tadpoles?
Gurdon found that the ability of a transplanted nucleus to direct normal development was inversely related to the age of the donor.
-Gurdon found that nuclei from older donor cells were unlikely to correctly direct differentiation.
All of the following are true regarding induced pluripotent stem (iPS) cells except _____.
iPS cells have been demonstrated to function identically to embryonic stems cells
All of the following are current applications of DNA technology in medicine except _____.
clinical use of iPS cells harvested from organ-impaired individuals for the culturing and transplantation of a functioning organ in the diseased individual
-Although iPS cell technology holds promise for this type of application, there is much we don’t know about how to direct iPS cells into specific cell types to form tissues and organs.
