Eukaryotic Gene Expression and Development

Flashcards for reviewing key concepts in eukaryotic gene expression and development.

What are tissue-specific genes?

Genes that are only active in some cell types and need to be turned off in others.

Define constitutive genes.

Genes that are expressed continuously and do not vary greatly in their expression, such as housekeeping genes.

What are regulated genes?

Genes whose expression varies greatly between different tissues or stages.

What are structural genes?

Genes whose products are involved in making a cell achieve its function, e.g., enzymes and collagen.

What role do regulatory genes play?

They encode proteins that influence the expression level of other genes, such as transcription factors.

What drives cell differentiation?

Regulatory sequences and their combinations, including enhancers and promoters.

What is the function of enhancers in gene regulation?

Enhancers bind tissue-specific transcription factors to drive gene expression.

How do silencers function in gene regulation?

Silencers bind tissue-specific repressors to inhibit gene expression.

What is a core promoter?

The region of DNA where the transcription machinery assembles to initiate transcription.

What is a Locus Control Region (LCR)?

A regulatory sequence that enhances the expression of linked genes in a tissue-specific manner.

Why are insulators important in gene expression?

Insulators limit the action range of enhancers, ensuring specific gene expression.

What happens in the absence of galactose in yeast?

GAL80 blocks GAL4 from activating transcription.

What is the purpose of Polycomb Group (PcG) proteins?

They create facultative heterochromatin to silence genes and maintain gene expression patterns.

What role do trithorax group (TrxG) proteins play?

They act as activators of gene expression, opposing Polycomb proteins.

What is the difference between pluripotent and totipotent cells?

Pluripotent cells can differentiate into several cell types, while totipotent cells can become any cell type.

What do maternal genes do in early embryonic development?

They establish key developmental pathways and gradients that influence early pattern formation.

Define morphogens in developmental biology.

Substances that direct developmental fates based on their concentration gradients.

What is the significance of the bicoid gradient?

It serves as a positional cue for establishing the anterior-posterior axis in Drosophila embryos.

What type of genes are activated by high levels of bicoid?

Gap genes, such as hunchback and giant.

What determines the expression of pair-rule genes?

Interactions between gradients of maternal morphogens like bicoid and hunchback.

Explain the concept of 'priming' in transcriptional regulation.

Certain transcription factors prepare genes for activation by binding to enhancers or promoters.

What happens during gastrulation?

The process where embryonic cells undergo migration and differentiation to form germ layers.

What is an example of a well-studied model organism for developmental biology?

Drosophila melanogaster, due to its short life cycle and genetic tractability.

What role do activator and repressor proteins play in transcription?

Activators enhance gene expression, while repressors inhibit it.

Define 'epigenetic regulation' in the context of gene expression.

The process by which gene expression is regulated by mechanisms that do not involve changes to the underlying DNA sequence.

What is the importance of the Sonic Hedgehog gene in development?

It is crucial for limb development and organ formation, regulated by multiple enhancers.

How is gene expression maintained across generations in a cellular lineage?

Through mechanisms such as DNA methylation and histone modification by PcG proteins.

What is the result of mutations in Polycomb proteins?

They can lead to tissue type transformations and misexpression of critical genes.

Why is gene expression considered a 'stop/go' mechanism?

It involves toggling between accessible (on) and inaccessible (off) chromatin states.

What effect do enhancers have on gene expression when combined with insulators?

Enhancers can activate transcription only for specific genes, depending on the positioning and effect of insulators.

How are gap genes and pair-rule genes related in Drosophila development?

Gap genes help establish initial segmentation, while pair-rule genes further refine the segmentation pattern.

What is the role of RNA polymerase in transcription?

RNA polymerase synthesizes RNA from the DNA template during transcription.