genetics ch 20 + 21
A bacterial polygenic transcription unit ________.
contains information for more than one protein product
BamHI cuts the sequence 5′ G|GATCC 3′. Which of the following sequences would not be recognized by this enzyme?
3′ TCTTAAG 5′ This sequence does not contain the BamHI recognition site.
If there are five molecules of DNA containing the target region at the beginning of a PCR reaction, how many copies of the target will be present after three rounds of amplification?
40 Correct. The number of target sequences is doubled with each replication cycle.
Which of the following DNA sequences is one strand of a restriction enzyme recognition sequence?
5' GGATCC 3'
The first step in annotating a gene is identifying the open reading frame. In bacteria, all genes that code for a protein have a start and stop codon with an open reading frame between them. A bioinformatics program can translate all the possible reading frames (series of 3 codons) in an attempt to find the longest open reading frame. How many possible open reading frames can a bioinformatics program translate from one DNA sequence? Enter your answer numerically (for example: 2).
6 Each strand of DNA has six possible reading frames. A reading frame is a series of 3 bases (codons) that can be used to predict an open reading frame. There are three reading frames in the 5'- 3' direction and three reading frames in the 3'- 5' direction. You can also think of it as three possible frames in one direction on each strand of DNA.
Within a six-base DNA recognition sequence, an enzyme that cuts between the 3rd and 4th bases from the 5' end will generate blunt ends.
True
The human genome contains approximately 20,000 protein-coding genes, yet it has the capacity to produce several hundred thousand gene products. What can account for the vast difference in gene number and product number?
Alternative splicing occurs.
The function of a ddNTP in DNA sequencing is to methylate guanine.
False
The genomic organization of all living creatures is identical.
False
The terms proteomics and genomics mean essentially the same thing.
False
Chromosome walking is used mainly to isolate a gene when the sequence of the gene is known.
False Chromosome walking is used mainly when the gene of interest has not yet been cloned but its approximate location on a chromosome is known.
Restriction endonucleases cut DNA at specific recognition sequences and then bond two strands covalently with the same "sticky ends."
False Restriction endonucleases cut DNA at specific sequences, but DNA ligase must be used to bond two strands covalently with the same "sticky ends."
DNA fragments that are 600 bp long will migrate more quickly through a sequencing gel than fragments that are 150 bp long.
False Small DNA fragments have less hindrance in moving through the gel, so they migrate more quickly than larger fragments.
The thermostability of Taq polymerase is required during the annealing phase of PCR.
False The annealing phase takes place at the lowest temperature of PCR. Taq polymerase is derived from bacteria that live in hot springs, so the enzyme is thermostable, meaning that its enzymatic properties can withstand the high temperatures needed for denaturation.
Which of the following statements about manual Sanger sequencing is true?
The DNA sequence obtained is complementary to the template strand. The DNA fragments produced in sequencing reactions are synthesized by DNA polymerase to be complementary to the template strand.
Which of the following elements is not found in a plasmid?
Lamba arms Lambda arms are regions that flank the inserted foreign DNA in phage λ vectors.
Which of the following molecules is not required for a PCR reaction? DNA DNTPs Ligase Primer
Ligase Ligase is not required for a PCR reaction. The enzyme used during PCR is a thermostable DNA polymerase.
How does shotgun cloning differ from the clone-by-clone method?
No genetic or physical maps of the genome are needed to begin shotgun cloning. Shotgun cloning randomly sequences clones with no prior knowledge of their location in the genome.
Why are filters overlaid with X‑ray film when screening a cDNA library?
To visualize probe hybridization events The X‑ray film allows probe hybridization events on the filter to be visualized if a radioactive probe is used.
A 1.5‑kb fragment of DNA is cloned into a plasmid vector that is 5.5 kb long at the EcoRI site, and the plasmid vector is then used to transform bacteria. If the plasmid DNA is then extracted from a single bacterial colony and digested with EcoRI, what digestion products will be produced if the plasmid contains the fragment?
One 1.5‑kb fragment and one 5.5‑kb fragment EcoRI digestion will produce two fragments corresponding in size to the 1.5‑kb fragment cloned into the plasmid plus the 5.5‑kb plasmid itself.
What is one major limitation of two-dimensional gel electrophoresis (2-DGE)?
Only the most abundant products are detected.
Words such as level, civic, and kayak have something in common compared to the fundamental tool of recombinant DNA technology. In the context of recombinant DNA technology, which term would be used to describe such words?
Palindromic
Digestion of a 1.1‑kb fragment of DNA with BamHI produces two fragments of 700 bp and 400 bp. Digestion of the same 1.1‑kb fragment with XhoI produces two fragments of 300 bp and 800 bp. Digestion with both enzymes produces three fragments of 100 bp, 300 bp, and 700 bp. Which of the following statements is true about the DNA fragment?
The XhoI site is located within the BamHI 400‑bp fragment. Since double digestion produces a 100‑bp fragment and a 300‑bp fragment, the XhoI site must be located within the BamHI 400‑bp fragment.
Which of the following statements about ddNTPs is true?
They have a hydrogen at the 3′ carbon of the sugar. ddNTPs terminate synthesis because there is no 3′‑hydroxyl group onto which DNA polymerase can add nucleotides.
What is the function of restriction endonucleases in bacteria?
They provide a defense mechanism against infection by viruses. Restriction endonucleases recognize and degrade viral DNA, thus preventing viral infections.
What is the purpose of raising the temperature to 90-95°C at the beginning of each cycle of PCR?
To separate the double‑stranded DNA The temperature is raised to denature the double‑stranded DNA molecule into single strands.
The study of orthologs would be useful to determine the function of a specific gene in a species.
True Because orthologs are descended from a common ancestral gene, they tend to have the same function in different species. If the function of a gene in one species were known, then its ortholog in a different species would most likely have that same function.
The products of restriction digestion can be visualized by gel electrophoresis, which separates fragments based on their size.
True Restriction digestion produces fragments of DNA, and the sizes of these fragments can be determined by gel electrophoresis using standard DNA fragments of known size.
Phage λ can carry larger DNA fragments than plasmids.
True Phage vectors can carry DNA fragments of about 20 kb, whereas plasmids can only carry DNA of less than 15 kb.
A DNA fragment is introduced into the lacZ gene of a plasmid, which also contains a tetracycline resistance gene. What is the appearance of bacteria transformed with this plasmid if they are spread on plates containing tetracycline and Xgal?
White colonies that are resistant to tetracycline The presence of blue colonies means that the plasmid taken up by these bacteria is recombinant, since the lacZ gene was disrupted.
The Human Genome Project, which got under way in 1990, is an international effort to ________.
determine the base sequence of the human genome and to identify all the genes within
One of the primary reasons for generating a large number of clones in a eukaryotic genomic library is that ________.
each vector can take up only a relatively small fraction of the eukaryotic DNA
List two especially useful characteristics of cloning vectors.
high copy number and antibiotic resistance gene(s)
X-Gal is included in the growth medium on which cells transformed with bacterial plasmids are grown. The reason X-Gal is included is to _______.
identify bacteria that contain a recombinant plasmid Correct. Colonies produced from cells containing a recombinant plasmid are white, whereas colonies from cells containing a nonrecombinant plasmid are blue.
Which of the following is a characteristic of the human genome?
larger and more intron-rich genes than in genomes of invertebrates Both gene size and intron content tend to increase with complexity of the organism.
Some vectors such as pUC18 and others of the pUC series contain a large number of restriction enzyme sites clustered in one region. Which term is given to this advantageous arrangement of restriction sites?
multiple cloning site
Proteomics is the ________.
process of defining the complete set of proteins encoded by a genome
What is the name of the process by which bacterial colonies (cells) are transferred from one agar plate to another, maintaining the same spatial pattern?
replica plating
Two-dimensional gel electrophoresis is used in proteomics to __________.
separate different proteins with high resolution Two-dimensional gel electrophoresis is used to separate proteins by first separating them based on charge and then separating them based on their molecular weight.
Restriction endonucleases are especially useful if they generate "sticky" ends. What makes an end sticky?
single-stranded complementary tails
What is metabolomics?
the analysis of proteins and enzymatic pathways involved in cell metabolism This is the correct definition of metabolomics.
Immediately after the primers have annealed to the target sequence, _______.
the temperature is raised so that taq polymerase can extend the primers Correct. The temperature is raised to 70-75∘C, the temperature over which taq polymerase is optimally active.
The role of the primers in PCR is _______.
to define the target region and provide a 3' end that can be extended by taq polymerase