Question

Local variations in secondary structure occur with ____________ ______________. These more subtle changes in topology of the DNA may be important in gene regulation.

Answer 1

Local variations in secondary structure occur with epigenetic regulation, which alters the folding and packaging of DNA without changing the sequence, and can affect gene accessibility and expression.

Step-by-step explanation:

Local variations in secondary structure of DNA occur with epigenetic regulation. These variations are important in gene regulation because they affect the physical structure of chromatin, which can influence the accessibility of genes for transcription. The secondary structure in proteins, such as the α-helix and β-pleated sheets, are stabilized by hydrogen bonds and are crucial in the protein's overall structure and function.

In the context of DNA and histones, these local structural changes do not alter the nucleotide sequence but instead modify how the DNA is packaged. Histones can move along DNA to change its structure, influencing whether the DNA is in an open or closed configuration. This in turn controls the access of transcription factors and RNA polymerase to the DNA for the transcription process. Epigenetic changes are heritable and reversible, allowing for different genes to be expressed as necessary.

Answer 2

Local variations in secondary structure involving histone modifications play a key role in gene regulation, influencing whether a gene is active or inactive by altering chromatin conformation without changing the DNA sequence itself.

Step-by-step explanation:

Local variations in secondary structure occur with histone modifications. These more subtle changes in the topology of the DNA may be important in gene regulation. The control of transcription involves transcription factors that recognize and bind to regulatory sequences in the DNA such as enhancers or silencers. These protein-DNA interactions often require selective structural changes in the conformation of the chromatin surrounding genes.

The secondary structure refers to highly regular local structures such as the alpha-helix and beta-pleated sheets, stabilized by hydrogen bonds within the polypeptide backbone. These structures are critical not just to protein function but also to the interactions with DNA that affect how genes are accessed and expressed. Epigenetics closely examines how these protein interactions in eukaryotes affect gene expression. Key facets of epigenetics include changes to histone proteins and DNA without altering the nucleotide sequence.

The role of these structural changes can have profound impacts on whether a gene is transcribed or silenced. For instance, modifications to histones and DNA surrounding a chromosomal region can 'open' or 'close' that region, thereby regulating access for RNA polymerase and transcription factors, which are essential for initiating transcription.