8 practice MCQs on DNA replication, transcription, translation, the genetic code, gene regulation and genetic engineering techniques. Every question has the correct answer and an explanation.
Start free — 20 questionsDNA and Gene Expression is part of the MDCAT Biology syllabus. This page collects DNA and Gene Expression MCQs in the style of past MDCAT papers — below are 8 of them with answers and explanations, and the full set of 8 questions is in the HighYield MDCAT QBank.
This chapter covers: DNA replication, transcription, translation, the genetic code, gene regulation and genetic engineering techniques.
Correct answer: C. Cytoplasm
Ribosomes exist either bound to the rough ER or freely dispersed in the cytoplasm, where they synthesize proteins used within the cell.
Correct answer: A. Protein
Ribosomes are the cellular structures responsible for synthesizing proteins by translating messenger RNA.
Correct answer: B. UAA
UAA is one of the three stop (terminating) codons in translation, signalling the ribosome to end protein synthesis.
Correct answer: A. Heating > Cooling > Add Primer > Copying of strand
The PCR cycle proceeds through heating (denaturation) to separate DNA strands, cooling to allow primer annealing, followed by copying (extension) of each strand.
Correct answer: A. E.Coli
Plasmids were discovered by investigators studying the sex life of the intestinal bacterium Escherichia coli.
Correct answer: D. RNA polymerase III
RNA polymerase II (Pol II) catalyzes the synthesis of mRNAs and some specialized RNAs. RNA Polymerase III synthesizes tRNAs, the 5S rRNA, and some other small specialized RNAs.
Correct answer: B. denaturation
During PCR (Polymerase Chain Reaction), DNA is separated through a process called denaturation. Denaturation is achieved by heating the DNA sample to a high temperature, typically around 94-98°C.
Correct answer: C. To stabilize the ribosomal structure
Ribosomes are complex structures made of RNA and proteins. The RNA molecules have a lot of negative charges due to their phosphate backbone. Mg²⁺ ions help to neutralize these charges, acting like a "glue" to hold the different components of the ribosome together. This stability is crucial for the ribosome to function properly
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