Chapter 20: DNA Technology and Genomics
The human genome is thought to contain about how many genes?
20,000-25,000
Once an organism's genome sequence has been determined, how do scientists generally start identifying all the genes within the genome?
Analyze the sequence using software that scans the sequence for telltale sequence elements such as promoters, transcription start and stop sites, and so on.
To create recombinant DNA with long-term stability, it is necessary to have which of the following in the test tube?
DNA ligase
Which one 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
Human nerve cells differ from human muscle cells because different sets of genes are expressed; in each type of cell, different genes are transcribed into mRNA and translated into protein. Which of the following techniques would be the most efficient way to identify the genes that these cells express?
DNA microarray assays
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 probably not be needed to do this?
F factors
A molecular biologist used a retroviral vector to introduce a gene coding for a certain human enzyme into mouse cells. One cell line was isolated that was able to make the human enzyme, but it had lost the ability to express an endogenous, normally expressed gene in the process. What is the best explanation for these results?
The virus inserted the gene encoding the human enzyme into the normally expressed endogenous gene.
A genetic marker is
a particular nucleotide sequence whose inheritance can be followed
In recombinant methods, the term "vector" refers to
a plasmid or other agent used to transfer DNA into a living cell
Which of the following would be considered a transgenic organism?
a rat with rabbit hemoglobin genes
What two enzymes are needed to produce recombinant DNA?
a restriction enzyme and a ligase
Southern blotting is
a technique used to study RFLPs
Gene therapy involves
adding a functioning version of a defective gene to the cells of an individual
The number of genes in an organism's genome is not a perfect indication of the organism's complexity because
all of the above alternative splicing can increase the number of polypeptides made from a single pre-mRNA. post-translational modifications can increase the types of proteins produced by a single gene. individual polypeptides can interact to form multiple types of protein complexes. individual genes can be expressed in more or less complex ways in different organisms.
DNA synthesized using an RNA template is called
cDNA
Bacteria use restriction enzymes to
destroy foreign DNA
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
A nucleic acid probe is used to
identify genes that have been inserted into bacterial plasmids or separated by electrophoresis
In genetic engineering, the highly active plasmid from Agrobacterium tumefaciens is used to
insert genes of interest into plant chromosomes
Which of the following is not a step of the Southern blotting procedure?
linking the DNA with DNA ligase
Separating DNA fragments by gel electrophoresis is useful for all of the following except
none of the above
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
Preparing a physical map of the genome involves
preparing a collection of large, overlapping genomic DNA fragments, and ordering them relative to each other
The dideoxyribonucleotide chain-termination method
produces a ladder of DNA fragments, with each individual band labeled with one of four different fluorescent tags
An enzyme that cuts DNA at a symmetrical sequence of bases is called a
restriction enzyme
What is the source of the reverse transcriptase used in recombinant DNA technology?
retroviruses
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
In genetic engineering, "sticky end" refers to
short bits of single-stranded DNA left at the end of DNA molecules cut by restriction enzymes
DNA fingerprints are used to determine whether Sam could be the father of Becky's baby. Sam is not the father if _____ genetic fingerprint shows some bands not present in _____ genetic fingerprint.
the baby's ... Sam's or Becky's
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
Transgenic organisms can be scientifically or commercially useful only if
the inserted ("foreign") gene is expressed in the host organism
DNA fingerprints used as evidence in a murder trial look something like supermarket bar codes. The pattern of bars in a DNA fingerprint shows
the presence of various-sized fragments of DNA
RFLPs have been tremendously useful for genomic mapping studies because
they are not restricted to genes, and are abundantly scattered throughout the genome
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
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