Test: Gene Control - 1 - MCAT MCQ

Alternative splicing is a post-transcriptional modification in which different exons of a gene can be selectively included or excluded during mRNA processing. This process allows for the production of multiple mRNA isoforms and different protein products from a single gene.

During transcription, RNA polymerase is responsible for unwinding the DNA double helix and synthesizing an RNA molecule using one of the DNA strands as a template. DNA polymerase (A) is primarily involved in DNA replication, while helicase (C) and topoisomerase (D) are involved in DNA unwinding and supercoiling regulation.

In the lac operon of E. coli, the repressor protein binds to the operator sequence and inhibits transcription when lactose is absent. The presence of an inducer molecule (C), such as lactose or allolactose, prevents the repressor protein from binding to the operator, allowing RNA polymerase (A) to transcribe the genes involved in lactose metabolism.

DNA methylation is an epigenetic modification that involves the addition of a methyl group to cytosine residues in DNA. Methylation can regulate gene expression by blocking the binding of transcription factors or recruiting proteins involved in chromatin remodeling, ultimately influencing transcription and gene control.

DNA methylation is a mechanism of transcriptional gene control that can influence gene expression by affecting the accessibility of DNA to transcription factors and RNA polymerase. It can lead to the repression or silencing of specific genes.

Transcription factors binding to enhancer regions can enhance gene expression by recruiting the transcriptional machinery and promoting the initiation of transcription. Enhancers are DNA sequences that can be located far from the gene they regulate and can interact with the promoter region to enhance transcriptional activity.

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression post-transcriptionally. They typically bind to complementary sequences in mRNA molecules and can lead to their degradation or inhibit their translation into proteins, thereby regulating gene expression.

Repressor proteins bind to specific DNA sequences, such as operator regions, and prevent the binding of RNA polymerase or other transcription factors to inhibit transcription. They play a role in negative regulation of gene expression.

Histone acetylation is an example of a global gene regulatory mechanism that affects chromatin structure and gene expression on a larger scale. It involves the addition of acetyl groups to histone proteins, leading to a more relaxed chromatin state and increased transcriptional activity.

Small interfering RNA (siRNA) molecules are key components of the RNA-induced silencing complex (RISC) involved in RNA interference (RNAi). siRNAs guide RISC to target mRNA molecules, leading to their degradation and silencing of gene expression.