Molecular Biology Essentials

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What is the purpose of DNA ligase in molecular cloning?

To join DNA fragments together by catalyzing the formation of phosphodiester bonds (correct)

To unwind the DNA double helix during replication

To transcribe mRNA from a DNA template

To degrade foreign DNA in a bacterial cell

Why must eukaryotes wait until transcription is complete before beginning translation?

To ensure proper binding of tRNA to the ribosome

To prevent interference from RNA polymerase during translation

To allow for the processing of pre-mRNA, including capping, splicing, and polyadenylation (correct)

To regulate the availability of ribosomes for translation

If a strain of E. coli has a mutation in the operator of the trp operon that prevents binding by a repressor, will the operon be transcribed in the presence of tryptophan?

No, the operon will not be transcribed

Depends on the presence of an activator

Yes, the operon will be transcribed (correct)

Depends on the absence of glucose

Why is the lac operon off by default in E. coli?

To avoid expression of genes for which the substrate is not available Signup and view all the answers

How are histone modifications used to alter the transcription of a gene?

By altering the accessibility of the DNA to transcription factors and RNA polymerase Signup and view all the answers

What is the difference between a general transcription factor and a specific transcription factor?

General transcription factors are common to all genes, while specific transcription factors are gene-specific Signup and view all the answers

What prevents an mRNA from existing in the cell forever and being translated forever?

Degradation by exonucleases Signup and view all the answers

How can a microRNA stop translation of a specific mRNA, but not all mRNAs in the cell?

By binding to the 3' UTR of the target mRNA Signup and view all the answers

What are the advantages or disadvantages for a eukaryote to regulate the amount or activity of a protein in a cell via transcriptional control vs. post-translational control?

Transcriptional control provides specificity, while post-translational control allows for long-term regulation Signup and view all the answers

What prevents alternative splicing from changing the order of exons in an mRNA transcript?

The genetic code restricts the order of exons Signup and view all the answers

Molecular Biology Essentials

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Questions and Answers

What is the purpose of DNA ligase in molecular cloning?

Why must eukaryotes wait until transcription is complete before beginning translation?

If a strain of E. coli has a mutation in the operator of the trp operon that prevents binding by a repressor, will the operon be transcribed in the presence of tryptophan?

Why is the lac operon off by default in E. coli?

How are histone modifications used to alter the transcription of a gene?

What is the difference between a general transcription factor and a specific transcription factor?

What prevents an mRNA from existing in the cell forever and being translated forever?

How can a microRNA stop translation of a specific mRNA, but not all mRNAs in the cell?

What are the advantages or disadvantages for a eukaryote to regulate the amount or activity of a protein in a cell via transcriptional control vs. post-translational control?

What prevents alternative splicing from changing the order of exons in an mRNA transcript?

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