Question

1. what type of bond is stronger than the thermal energies of random collisions and keeps organic molecules together? a. noncovalent bond b. hydrogen bond c. ionic bond d. covalent bond e. van der waals attraction 02. what process is a mechanism for generating proteins with different functions from a single gene? a. histone modification b. post - translational modification c. alternative splicing d. mrna polyadenylation e. ubiquitin tagging 03. in eukaryotic gene expression control, which step is cited as the most common control point? a. post - translational modification control b. transcriptional control c. mrna export control d. translation control e. protein degradation control 04. given that dna is compacted into chromatin (dna + proteins) and that nucleosomes contain dna and histones in a tight complex. if a cell needs to rapidly initiate transcription for a gene, which prerequisite step is mandatory? a. the dna must be permanently converted into heterochromatin. b. nucleosomes must be opened to make the dna sequence accessible to rna polymerase. c. the ctd of rnap - ii must be unphosphorylated. d. the gene must be moved to a different chromosome. e. the cell must utilize alternative splicing immediately. 05. if a cell lacks the tata binding protein (tbp), what is the most severe and predictable consequence for the cell? a. inability to synthesize trna. b. inability to assemble the preinitiation complex, thus preventing rnap - ii transcription of highly expressed genes. c. immediate degradation of all existing proteins. d. failure of chromatin remodeling. e. constant activity of the tryptophan operon.

Explanation:

Question 01:

Covalent bonds result from the sharing of electron pairs between atoms and are strong enough to keep organic molecules together, surpassing the thermal energies of random collisions. Noncovalent bonds, hydrogen bonds, ionic bonds, and Van der Waals attractions are generally weaker.

Question 02:

Alternative splicing is a process where different combinations of exons in a pre - mRNA are joined together, leading to the generation of multiple protein isoforms with different functions from a single gene. Histone modification affects chromatin structure, post - translational modification modifies proteins after they are synthesized, mRNA polyadenylation is related to mRNA stability, and ubiquitin tagging is for protein degradation.

Question 03:

Transcriptional control is the most common step in eukaryotic gene expression control as it determines whether a gene is transcribed into mRNA or not, thus regulating the amount of gene product. Post - translational modification control, mRNA export control, translation control, and protein degradation control are also important but less common as the primary control points.

Question 04:

For rapid transcription initiation, nucleosomes must be opened to expose the DNA sequence so that RNA polymerase can access it. Heterochromatin is tightly packed and transcriptionally inactive. Phosphorylation of the CTD of RNAP - II is important for transcription elongation, and moving the gene to a different chromosome or using alternative splicing immediately are not the mandatory prerequisites for rapid transcription initiation.

Question 05:

The TATA - binding protein (TBP) is a key component of the transcription pre - initiation complex. Without TBP, the pre - initiation complex cannot assemble properly, preventing RNAP - II transcription of highly expressed genes. It is not directly related to tRNA synthesis, immediate protein degradation, chromatin remodeling, or the activity of the tryptophan operon.

Answer:

1. d. Covalent bond
2. c. Alternative splicing
3. b. Transcriptional control
4. b. Nucleosomes must be opened to make the DNA sequence accessible to RNA polymerase.
5. b. Inability to assemble the preinitiation complex, thus preventing RNAP - II transcription of highly expressed genes.