Molecular Basis of Inheritance: MCQ Test

121. For initiation of translation, the ribosome binds to the mRNA at the start codon (AUG) that is recognized only by what?

• The release factor
• The elongation factor
• The initiator tRNA
• The ribosomal proteins

122. At the end of translation, what binds to the stop codon, terminating translation and releasing the complete polypeptide from the ribosome?

• Initiator tRNA
• Elongation factor
• Release factor
• Ribozyme

123. In eukaryotes, at which levels can gene expression be regulated?

• Transcriptional level (formation of primary transcript)
• Processing level (regulation of splicing)
• Transport of mRNA from nucleus to the cytoplasm
• Translational level
• All of the above

124. What conditions regulate the expression of genes in simple terms?

• Only genetic factors
• Only environmental factors
• Metabolic, physiological or environmental conditions
• Only developmental stages

125. In prokaryotes, what is the predominant site for control of gene expression?

• Processing level
• Translational level
• Control of the rate of transcriptional initiation
• Transport of mRNA

126. What are the accessory proteins that regulate the activity of RNA polymerase at a promoter in prokaryotes, and how can they act?

• Activators (positively) and repressors (negatively)
• Only activators
• Only repressors
• Enzymes that degrade RNA polymerase

127. In prokaryotes, what are the sequences adjacent to promoter elements that bind repressor proteins called?

• Enhancers
• Silencers
• Operators
• Terminators

128. Who were the first to elucidate a transcriptionally regulated system, specifically the lac operon?

• James Watson and Francis Crick
• Alfred Hershey and Martha Chase
• Francois Jacob and Jacque Monod
• Matthew Meselson and Franklin Stahl

129. What term refers to an arrangement common in bacteria where a polycistronic structural gene is regulated by a common promoter and regulatory genes?

• Cistron
• Regulon
• Operon
• Genome

130. The lac operon consists of one regulatory gene and three structural genes. What are they?

• i gene; z, y, a genes
• p gene; o, c, r genes
• i gene; lacA, lacB, lacC genes
• r gene; trp, his, val genes

131. What does the 'i gene' in the lac operon code for?

• Inducer
• Initiator
• Inhibitor (repressor)
• Integrase

132. What enzyme does the 'z gene' of the lac operon code for, and what is its primary function?

• Permease, increases cell permeability
• Beta-galactosidase, hydrolyses lactose
• Transacetylase, acetylates lactose
• Repressor, inhibits transcription

133. What enzyme does the 'y gene' of the lac operon code for, and what is its function?

• Beta-galactosidase, hydrolyses lactose
• Permease, increases permeability of the cell to β-galactosides
• Transacetylase, acetylates lactose
• Repressor, inhibits transcription

134. What enzyme does the 'a gene' of the lac operon code for?

• Beta-galactosidase
• Permease
• Transacetylase
• Repressor

135. What acts as the inducer for the lac operon?

• Glucose
• Galactose
• Lactose (or allolactose)
• Repressor protein

136. In the absence of an inducer like lactose, what happens to the repressor protein synthesized from the 'i gene'?

• It binds to the promoter
• It binds to the operator region of the operon and prevents RNA polymerase from transcribing
• It enhances transcription
• It is degraded

137. In the presence of an inducer like lactose, how does it affect the repressor of the lac operon?

• It activates the repressor
• It inactivates the repressor by interaction
• It causes the repressor to bind more strongly to the operator
• It has no effect

138. Regulation of the lac operon by the repressor is referred to as what type of regulation?

• Positive regulation
• Negative regulation
• Inducible regulation
• Constitutive regulation

139. In what year was the ambitious project of sequencing the human genome launched?

• 1980
• 1990
• 2000
• 2003

140. What was the initial estimated cost of the Human Genome Project?

• $3 billion US dollars
• $6 billion US dollars
• $9 billion US dollars
• $12 billion US dollars