Chapter Exam

Chapter 1: An Overview of Recombinant DNA Technology — Online MCQ Test

Q: Recombinant DNA technology mainly involves the formation of DNA molecules by joining DNA from:

Answer: A. Two different sources — Recombinant DNA is formed by joining DNA fragments from two different sources, often from different organisms.

Q: Which enzyme is commonly called molecular scissors in recombinant DNA technology?

Answer: B. Restriction endonuclease — Restriction endonucleases cut DNA at specific recognition sequences and are therefore called molecular scissors.

Q: The enzyme used to join DNA fragments during recombinant DNA formation is:

Answer: A. DNA ligase — DNA ligase joins DNA fragments by forming phosphodiester bonds between adjacent nucleotides.

Q: A plasmid used in genetic engineering is generally a:

Answer: A. Circular extrachromosomal DNA molecule — Plasmids are small circular extrachromosomal DNA molecules commonly used as cloning vectors.

Q: A researcher ligates a human gene into the middle of an antibiotic resistance gene of a plasmid. What is the most likely effect on that resistance gene?

Answer: A. It becomes insertionally inactivated — Insertion of foreign DNA within a functional marker gene can disrupt it, a principle called insertional inactivation.

BIOTECHNOLOGY · Grade 12 · CBSE(NCERT)

Practice Chapter 1: An Overview of Recombinant DNA Technology with a free chapter-wise online MCQ test for CBSE(NCERT) Grade 12 BIOTECHNOLOGY. This chapter covers: Recombinant DNA Genetic Engineering DNA Isolation DNA Modification Gene Splicing Recombinant Molecules Human Insulin Therapeutic Proteins Restriction Enzymes Biotechnology. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 1: An Overview of Recombinant DNA Technology — Important Questions & Answers (FAQ)

Frequently asked questions from CBSE(NCERT) Grade 12 BIOTECHNOLOGY — Chapter 1: An Overview of Recombinant DNA Technology, with answers and explanations. These are sample questions; the exam has its own separate question set.

Recombinant DNA technology mainly involves the formation of DNA molecules by joining DNA from:

A. Two different sources ✓
B. Only identical cells
C. Only RNA viruses
D. Only mitochondria

Answer: A. Two different sources
Recombinant DNA is formed by joining DNA fragments from two different sources, often from different organisms.

Which enzyme is commonly called molecular scissors in recombinant DNA technology?

A. DNA ligase
B. Restriction endonuclease ✓
C. DNA polymerase
D. Reverse transcriptase

Answer: B. Restriction endonuclease
Restriction endonucleases cut DNA at specific recognition sequences and are therefore called molecular scissors.

The enzyme used to join DNA fragments during recombinant DNA formation is:

A. DNA ligase ✓
B. Amylase
C. Helicase
D. Protease

Answer: A. DNA ligase
DNA ligase joins DNA fragments by forming phosphodiester bonds between adjacent nucleotides.

A plasmid used in genetic engineering is generally a:

A. Circular extrachromosomal DNA molecule ✓
B. Linear RNA molecule
C. Protein coat of a virus
D. Carbohydrate polymer

Answer: A. Circular extrachromosomal DNA molecule
Plasmids are small circular extrachromosomal DNA molecules commonly used as cloning vectors.

A student wants to clone a gene in a plasmid. Which sequence of steps is most appropriate?

A. Cut vector and insert, ligate them, introduce into host cells ✓
B. Introduce vector into host, cut host chromosome, ligate proteins
C. Translate gene, cut protein, insert into plasmid
D. Ligate intact cells, cut plasmid, isolate amino acids

Answer: A. Cut vector and insert, ligate them, introduce into host cells
In cloning, the gene insert and vector are cut with suitable restriction enzymes, joined using ligase, and introduced into host cells.

Sticky ends are useful in recombinant DNA technology because they:

A. Prevent DNA replication
B. Help complementary DNA ends anneal before ligation ✓
C. Destroy plasmid vectors
D. Convert DNA into RNA

Answer: B. Help complementary DNA ends anneal before ligation
Sticky ends have short single-stranded overhangs that can base-pair with complementary ends, making ligation easier.

A researcher ligates a human gene into the middle of an antibiotic resistance gene of a plasmid. What is the most likely effect on that resistance gene?

A. It becomes insertionally inactivated ✓
B. It becomes a restriction enzyme
C. It duplicates the bacterial chromosome
D. It converts into mRNA permanently

Answer: A. It becomes insertionally inactivated
Insertion of foreign DNA within a functional marker gene can disrupt it, a principle called insertional inactivation.

Two DNA samples are cut with EcoRI. One is a plasmid and the other contains the target gene. Why is EcoRI suitable for preparing recombinant DNA in this case?

A. It produces complementary sticky ends in both DNA samples ✓
B. It converts plasmid DNA into protein
C. It prevents any DNA ligation
D. It removes the need for a host cell

Answer: A. It produces complementary sticky ends in both DNA samples
When both DNAs are cut with the same enzyme like EcoRI, their sticky ends are complementary and can be joined by DNA ligase.

A DNA sequence reads 5'-GAATTC-3' on one strand and 3'-CTTAAG-5' on the other. Why is it important for EcoRI?

A. It is a palindromic recognition sequence cut by EcoRI ✓
B. It is a codon sequence for insulin only
C. It is the bacterial origin of replication
D. It is a protein sequence recognized by ligase

Answer: A. It is a palindromic recognition sequence cut by EcoRI
EcoRI recognizes the palindromic sequence GAATTC and cuts it to produce sticky ends.

A cloning experiment gives many antibiotic-resistant colonies, but only some contain the desired insert. Which approach is most directly used to distinguish recombinants from non-recombinants in basic plasmid cloning?

A. Screening based on insertional inactivation of a marker gene ✓
B. Counting the number of ribosomes in each colony
C. Measuring the thickness of bacterial cell walls
D. Selecting colonies that cannot replicate DNA

Answer: A. Screening based on insertional inactivation of a marker gene
Antibiotic resistance shows plasmid uptake, while insertional inactivation or similar screening methods help identify plasmids carrying the insert.

Next Chapter →

Chapter 2: Host Vector System