Gene Expression and Chromatin Structure

These flashcards cover key concepts related to gene expression and chromatin structure as discussed in the lecture.

What is non-disjunction?

Failure of homologous chromosomes to separate in meiosis or mitosis.

Chromatin is:

A complex of nucleic acids (e.g., DNA or RNA) and proteins (histones).

What mechanism(s) can influence nucleosome stability and dynamics?

DNA sequences, post-translational modifications on histones, and pioneering transcription factors or chromatin remodeling factors.

Neutralizing the positive charges of histones would have what effect on the histone proteins?

They would bind less tightly to the DNA.

A chromosomal duplication can provide:

Gene redundancy, phenotypic variation that confers adaptive potential, and a source of new genetic material on which evolutionary selection acts.

What refers to the phenomenon in which small sections of the genome are repeated, and the number of repeats varies among individuals?

Copy number variation.

A human male with the chromosome constitution of XXXYY would contain how many Barr bodies in his somatic cells?

1.

What is the Shine-Dalgarno sequence?

The ribosome binding site in bacterial RNA.

Which aspect of gene expression regulation in eukaryotes differs from prokaryotes?

The processes of transcription and translation are uncoupled.

In eukaryotic cells, where does the basal transcription apparatus bind?

Core promoter.

Most transcriptional activator proteins affect transcription by interacting with:

The basal transcription machinery.

Cis-acting elements such as enhancers have all the following characteristics except:

Are always located 75 bp upstream of the transcription start site.

What is the difference between the core promoter and the regulatory region?

Transcription basal factors bind to the core promoter; transcriptional activator proteins bind to the regulatory regions.

A single transcription factor can regulate gene expression by:

In response to external signals, during specific times in development, and in a tissue-specific manner.

Two types of post-transcriptional modifications that take place in RNA transcripts of eukaryotes are:

Addition of a cap at the 5' end and addition of a poly A sequence at the 3' end.

What is the function of the poly(A) tail?

Protects mRNA from degradation.

MicroRNAs are:

Small RNA molecules that bind to coding mRNAs and prevent protein translation.

What does a complex of miRNA and Argonaute form?

RISC, which induces degradation or translational repression of target mRNAs.

Which statement best describes the distinction between miRNAs and siRNAs?

siRNAs are exogenously provided and highly specific; miRNA-mediated silencing is an endogenous process.

RNA editing is:

A process through which cells can make changes to specific nucleotide sequences within an RNA molecule.

What would happen if there was a mutation in the 5' consensus sequence during splicing?

U1 would not bind, and splicing would not occur.

What mechanism provides for tissue-specific alternative splicing in different tissues?

A tissue-specific RNA-binding protein prevents the inclusion of specific exons.

What is a common physical modification on histones in euchromatin?

Acetylation.

What is defined as the equalization of the amount of protein produced by X-linked genes in males and females?

Dosage compensation.

What is epigenetic regulation?

Processes that control gene activity without altering the DNA sequence itself.

What is the consequence of changes to histone proteins?

They can change the accessibility of surrounding genes and thus influence gene expression.

Name one potential advantage and disadvantage of positive regulation in gene expression.

Advantage: Conserves energy by only transcribing necessary genes. Disadvantage: Delayed response in protein production.

What is one advantage and disadvantage of alternative splicing?

Advantage: Saves space in the genome and produces multiple protein forms. Disadvantage: A mutation can disrupt production of many proteins.