Dow University MDCAT / Entry Test Biology Biotechnology — Set 3

Dow University MDCAT / Entry Test Biology Biotechnology — Set 3

1. Question 1

   Q1. In genetic engineering, what is an exception to the typical function of a selectable marker?

   • A) It always confers antibiotic resistance
   • B) It can be used to identify recombinant cells
   • C) It sometimes causes insertional inactivation
   • D) It is always constitutively expressed

   Answer: It sometimes causes insertional inactivation

   Explanation: Selectable markers can cause insertional inactivation when a gene is inserted within them, disrupting their function.

2. Question 2

   Q2. A gene of interest is cloned into a plasmid vector. What is a common method to confirm successful cloning?

   • A) PCR of the insert
   • B) Restriction digestion analysis
   • C) DNA sequencing
   • D) All of the above methods are used

   Answer: All of the above methods are used

   Explanation: Multiple methods are used to confirm cloning success, including PCR, restriction digestion, and DNA sequencing.

3. Question 3

   Q3. Why are retroviruses used as vectors in gene therapy?

   • A) They can integrate into the host genome
   • B) They are non-pathogenic
   • C) They have a DNA genome
   • D) They are easy to culture

   Answer: They can integrate into the host genome

   Explanation: Retroviruses integrate into the host genome, allowing for stable expression of the therapeutic gene; They are actually pathogenic.

4. Question 4

   Q4. What is a characteristic of DNA ligase used in genetic engineering?

   • A) It requires a template
   • B) It seals nicks in double-stranded DNA
   • C) It is specific to blunt ends
   • D) It requires ATP or NAD+ as a cofactor

   Answer: It requires ATP or NAD+ as a cofactor

   Explanation: DNA ligase requires ATP (or NAD+ in some cases) to form a phosphodiester bond; It seals nicks, not just specific to blunt ends.

5. Question 5

   Q5. In biotechnology, what is the purpose of using a cDNA library?

   • A) To clone genomic DNA
   • B) To study gene expression in different tissues
   • C) To amplify a specific gene
   • D) To identify protein-protein interactions

   Answer: To study gene expression in different tissues

   Explanation: cDNA libraries represent expressed genes, allowing study of gene expression across different tissues; They lack introns.

6. Question 6

   Q6. A scientist is using Agrobacterium tumefaciens to transfer a gene into plant cells. What is being exploited?

   • A) The bacterium's ability to cause disease
   • B) The Ti plasmid's ability to transfer DNA
   • C) The plant's ability to undergo regeneration
   • D) The bacterium's ability to photosynthesize

   Answer: The Ti plasmid's ability to transfer DNA

   Explanation: Agrobacterium's Ti plasmid is used for gene transfer; The natural ability of Ti plasmid to transfer T-DNA is exploited.

7. Question 7

   Q7. What is an unusual feature of some restriction enzymes?

   • A) They cut at non-palindromic sequences
   • B) They produce blunt ends
   • C) They are isolated from psychrophilic bacteria
   • D) They require ATP for activity

   Answer: They cut at non-palindromic sequences

   Explanation: Some restriction enzymes cut at non-palindromic sequences; Most cut at palindromic sequences.

8. Question 8

   Q8. Why is it advantageous to use a thermostable DNA polymerase in PCR?

   • A) It increases the yield of the product
   • B) It reduces non-specific binding
   • C) It allows for higher annealing temperatures
   • D) It withstands the high temperatures of the denaturation step

   Answer: It withstands the high temperatures of the denaturation step

   Explanation: Thermostable DNA polymerase withstands denaturation temperatures, remaining active; It is essential for PCR.

9. Question 9

   Q9. In genetic engineering, what is the role of a promoter in an expression vector?

   • A) To terminate transcription
   • B) To initiate translation
   • C) To regulate the timing and level of gene expression
   • D) To enhance the stability of the mRNA

   Answer: To regulate the timing and level of gene expression

   Explanation: Promoters regulate the timing and level of gene expression by controlling transcription initiation; They are crucial for expression vectors.

10. Question 10

    Q10. What is a major limitation of using bacteria as hosts for cloning large DNA fragments?

    • A) Bacteria cannot take up large DNA molecules
    • B) Large DNA fragments are unstable in bacteria
    • C) Bacteria lack the machinery to replicate large DNA
    • D) Large DNA inserts often disrupt bacterial viability

    Answer: Large DNA fragments are unstable in bacteria

    Explanation: Large DNA fragments can be unstable in bacteria due to potential for recombination or deletion; Special vectors like BACs help mitigate this.

11. Question 11

    Q11. Why are yeast artificial chromosomes (YACs) used?

    • A) To clone small DNA fragments
    • B) To express proteins in bacteria
    • C) To clone very large DNA fragments
    • D) To sequence genomes

    Answer: To clone very large DNA fragments

    Explanation: YACs are used to clone very large DNA fragments; They can hold inserts of up to 2 Mb.

12. Question 12

    Q12. In gene therapy, what is a challenge associated with using viral vectors?

    • A) They are too efficient at delivering genes
    • B) They can cause immune responses
    • C) They are too expensive to produce
    • D) They cannot infect human cells

    Answer: They can cause immune responses

    Explanation: Viral vectors can cause immune responses, posing a challenge; This can lead to inflammation and other complications.

13. Question 13

    Q13. What is a feature of the CRISPR-Cas9 system that makes it useful for gene editing?

    • A) It is highly specific to target sequences
    • B) It can only edit genes in prokaryotes
    • C) It requires a complex setup with many enzymes
    • D) It is limited to editing single genes

    Answer: It is highly specific to target sequences

    Explanation: CRISPR-Cas9 is highly specific due to guide RNA; This specificity makes it a powerful gene editing tool.

14. Question 14

    Q14. Why might a scientist prefer to use a BAC (Bacterial Artificial Chromosome) over a plasmid for cloning?

    • A) BACs are easier to manipulate
    • B) BACs can hold larger DNA inserts
    • C) BACs replicate more quickly
    • D) BACs are more stable in mammalian cells

    Answer: BACs can hold larger DNA inserts

    Explanation: BACs can hold larger DNA inserts; They are used for cloning large genomic fragments.

15. Question 15

    Q15. In biotechnology, what is an advantage of using electroporation for DNA transfer?

    • A) It is highly specific to certain cell types
    • B) It is a chemical method
    • C) It can efficiently transfer DNA into a wide range of cells
    • D) It is limited to transferring small DNA molecules

    Answer: It can efficiently transfer DNA into a wide range of cells

    Explanation: Electroporation efficiently transfers DNA into various cell types; It works by creating temporary pores in the cell membrane.

16. Question 16

    Q16. What is a potential risk associated with the use of retroviral vectors in gene therapy?

    • A) Insertional mutagenesis
    • B) Off-target effects
    • C) Reversion to virulence
    • D) Induction of autoimmune responses

    Answer: Insertional mutagenesis

    Explanation: Retroviral vectors can cause insertional mutagenesis by integrating into the host genome; This can disrupt gene function.

17. Question 17

    Q17. Why are molecular beacons used in real-time PCR?

    • A) To amplify the target DNA
    • B) To detect the presence of the target DNA
    • C) To increase the specificity of the PCR reaction
    • D) To label the PCR product for later analysis

    Answer: To detect the presence of the target DNA

    Explanation: Molecular beacons detect the presence of target DNA; They fluoresce when bound to the target sequence.

18. Question 18

    Q18. In genetic engineering, what is the significance of the multiple cloning site (MCS) in a plasmid vector?

    • A) It provides a site for the origin of replication
    • B) It contains a selectable marker
    • C) It allows for the insertion of foreign DNA at various restriction sites
    • D) It enhances the stability of the plasmid

    Answer: It allows for the insertion of foreign DNA at various restriction sites

    Explanation: MCS allows for the insertion of foreign DNA at multiple restriction sites; It facilitates cloning.

19. Question 19

    Q19. In genetic engineering, the primary difference between a plasmid and a cosmid is their ability to clone

    • A) smaller DNA fragments
    • B) larger DNA fragments
    • C) any size DNA fragment equally
    • D) only viral DNA

    Answer: larger DNA fragments

    Explanation: Cosmids can clone larger DNA fragments (up to 40 kb) compared to plasmids (up to 10 kb).

20. Question 20

    Q20. A scientist is comparing the processes of DNA sequencing and DNA fingerprinting. Which technique is more likely to identify a specific gene mutation?

    • A) DNA fingerprinting
    • B) DNA sequencing
    • C) PCR
    • D) Gel electrophoresis

    Answer: DNA sequencing

    Explanation: DNA sequencing directly determines the nucleotide sequence, allowing for the identification of specific gene mutations.