When the phage DNA enters a bacterium, it protects itself from the viral DNA with the help of:
1. | methylases | 2. | endonucleases |
3. | exonucleases | 4. | ligases |
The enzyme used in the polymerase chain reaction is a:
1. DNA dependent RNA polymerase
2. RNA dependent DNA polymerase
3. DNA dependent DNA polymerase
4. RNA dependent RNA polymerase
An important limitation of the use of Agrobacterium tumefaciens is that it cannot:
1. | infect dicots |
2. | be genetically modified |
3. | be cultured on a nutrient medium |
4. | infect crop plants such as wheat and corn |
Identify a character that is not desirable in a cloning vector:
1. | an inactive promoter |
2. | an origin of the replication site |
3. | selectable markers such as genes for antibiotic resistance |
4. | one or more unique restriction endonuclease sites |
Restriction enzymes are synthesized by:
1. | bacteria only | 2. | yeast and bacteria |
3. | eukaryotic cells only | 4. | all kinds of cells |
A cloning vector has two antibiotic resistance genes- for tetracycline and ampicillin. A foreign DNA was inserted into the tetracycline gene. Non-recombinants transformants would survive on the medium containing:
1. ampicillin but not tetracycline
2. tetracycline but not ampicillin
3. both tetracycline and ampicillin
4. neither tetracycline nor ampicillin
The first type II restriction endonuclease discovered that could cut dsDNA at a specific site was:
1. | EcoRI | 2. | SmaI |
3. | Hind II | 4. | Hind III |
Using reverse transcriptase or gene synthesis has an advantage over the shotgun approach in obtaining a copy of the gene required as:
1. | the gene produced can easily be ligated to the vector |
2. | the gene produced is not a split gene |
3. | the gene produced does not require a promoter to be expressed |
4. | the gene produced does not require an ori to replicate |
Elution is:
1. | separating the restricted DNA fragments on agarose gel |
2. | staining the separated DNA fragments with ethidium bromide |
3. | cutting out of the separated bands of DNA from the agarose gel and extracting them from the gel piece |
4. | constructing rDNA by joining the purified DNA fragments to the cloning vector |
When isolating the pure DNA from a bacterial cell, the cell should not be treated with:
1. | lysozyme | 2. | proteases |
3. | ribonuclease | 4. | deoxyribonuclease |
A host cell normally does not take up a foreign DNA until it has been made competent to do so. This is because:
1. | DNA is a hydrophilic molecule |
2. | DNA is a very large molecule |
3. | there are no receptors for DNA on the cell membrane |
4. | DNA is an inert molecule |
How does the bacterium protects its own DNA from the action of restriction endonucleases present in its cytoplasm?
1. | its DNA lacks active sites for the restriction endonucleases |
2. | its DNA is protected within a nuclear envelope |
3. | it adds methyl groups to the active sites of restriction endonucleases on its DNA |
4. | the DNA gets heterochromatised to prevent the action of restriction enzymes |
When “sticky ends” are paired, they can be joined by:
1. | restriction enzymes | 2. | polymerases |
3. | methylase | 4. | DNA ligase |
A danger of genetic engineering is that the genetically modified bacterium can escape the lab and infect humans. This possibility is prevented by:
1. | selecting a mutant form of the bacteria |
2. | selecting a live attenuated bacterium |
3. | application of stringent asepsis in the lab |
4. | prophylactically immunizing the persons working in the lab |
A DNA library is:
1. | information in a computer database about all the genes sequenced so far |
2. | a collection of vectors in a molecular biology lab |
3. | a collection of fragments of DNA that make up the entire genome of an organism |
4. | all the restriction sites put together on a DNA fragment |
A foreign DNA was introduced at a cloning site within the gene for beta-galactosidase in a plasmid of a bacterium. The bacterium containing this rDNA was plated on a medium containing X-gal. They were distinguished by the fact that they remained white. This method should be called as:
1. | selection | 2. | screening |
3. | transformation | 4. | transduction |
Cohen and Boyer constructed one of the first genetically engineered chimeras, pSC101. They introduced in this plasmid the gene of Xenopus laevis that coded for:
1. | cytochrome c | 2. | haemoglobin |
3. | keratin | 4. | rRNA |
Which of the following is not a plasmid?
1. | pSC101 | 2. | pUC18 |
3. | BamHI | 4. | pBR322 |
Identify the incorrectly matched pair:
restriction enzyme recognition site
1. EcoRI 5’GAATTC3’
3’CTTAAG5’
2. HindII 5’GTPyPuAC3’
3’CAPuPyTG3’
3. SmaI 5’GGATTC3’
3’CTTAGG5’
4. HindIII 5’AAGCTT3’
3’TTCGAA5’
Which of the following restriction enzymes would not produce “sticky ends”?
1. | EcoRI | 2. | HindII |
3. | BamHI | 4. | HindIII |
If the required gene has been isolated by shotgun approach, care must be taken to:
1. | cut the plasmid with a different restriction enzyme than that used to obtain the donor gene |
2. | cut the plasmid with the same restriction enzyme that was used to obtain the donor gene |
3. | avoid cutting the plasmid |
4. | cut the plasmid with two different restriction enzymes |
The chronological steps of a polymerase chain reaction are:
1. | Denaturation, Annealing of primers, Primer extension |
2. | Annealing of primers, Denaturation, Primer extension |
3. | Annealing of primers, Primer extension, Denaturation |
4. | Denaturation, Primer extension, Annealing of primers |
Taq polymerase is used in the polymerase chain reaction because:
1. | It replicates DNA faster than other enzymes |
2. | It is the only enzyme that can replicate DNA invitro |
3. | It does not require an RNA primer to function |
4. | It is thermostable |
A major advantage of using YAC as a cloning vector over the plasmids is that:
1. it can replicate independently
2. it can be selected easily
3. it can accommodate larger inserts
4. it has multiple cloning sites
Which of the following is normally not used as a method of introduction of
foreign DNA into an animal cell?
1. | Microinjection | 2. | Liposomes |
3. | Biolistics | 4. | Transfection |