Chapter 8

What is the key concept of gene expression in multicellular organisms?

All cells in a multicellular organism share the same DNA, but different cell types express different proteins.

What regulates gene expression?

Gene expression is regulated at multiple steps: from DNA to RNA to protein.

What are the two types of chromatin that affect gene expression?

Euchromatin, which is actively expressed, and heterochromatin, which is often silenced.

What is alternative splicing?

A process that allows a single gene to generate multiple mRNA transcripts by including or excluding certain exons.

What determines the phenotype of an organism?

Phenotype is determined by the genotype (the collection of its genes) and the environment.

What are transcriptional regulators?

Proteins that bind to DNA sequences to control the transcription of genes.

How do prokaryotes regulate gene expression?

Prokaryotes regulate gene expression through operons, which are clusters of genes transcribed as a single mRNA.

What is the function of repressors in gene expression?

Repressors turn genes off by binding to operators in DNA, blocking RNA polymerase from initiating transcription.

How do eukaryotic transcription regulators act?

Eukaryotic transcription regulators can bind to regulatory sequences that may be far from the promoter and influence transcription initiation.

What role do chromatin-modifying proteins play in gene transcription?

Chromatin-modifying proteins alter the structure of chromatin to either promote or inhibit access to the DNA by transcription factors and RNA polymerase.

What is the 'lac operon' and its significance?

The lac operon is a set of genes in E. coli that are regulated by both an activator and a repressor, serving as a model for understanding gene regulation.

What are microRNAs (miRNAs)?

Short RNA molecules that can base-pair with mRNAs to regulate their stability and translation.

What is the role of RISC in gene regulation?

RISC (RNA-Induced Silencing Complex) seeks and destroys RNAs that are complementary to its bound miRNA.

What is the significance of DNA methylation in gene expression?

Methylation can silence gene expression by attracting repressor proteins and is maintained through cell divisions.

How do transcriptional activators function?

Transcriptional activators bind to enhancers and facilitate the recruitment of additional transcription machinery to the promoter.

What is combinatorial control in gene expression?

The use of multiple transcription regulators that work together to control the expression of genes at different points in time.