Changes in epigenetic modifications alter the accessibility...

Changes in epigenetic modifications alter the accessibility and transcription of DNA. Describe how environmental stimuli, such as ultraviolet light exposure, could modify gene expression. a. UV rays could cause methylation and deacetylation of the genes that could alter the accessibility and transcription of DNA. b. The UV rays could cause phosphorylation and acetylation of the DNA and histones which could alter the transcriptional capabilities of the DNA. c. UV rays could cause methylation and phosphorylation of the DNA bases which could become dimerized rendering no accessibility of DNA. d. The UV rays can cause methylation and acetylation of histones making the DNA more tightly packed and leading to inaccessibility.

Changes in epigenetic modifications alter the accessibility and transcription of DNA. Describe how
environmental stimuli, such as ultraviolet light exposure, could modify gene expression.
a. UV rays could cause methylation and deacetylation of the genes that could alter the accessibility and transcription of DNA.
b. The UV rays could cause phosphorylation and acetylation of the DNA and histones which could alter the transcriptional capabilities of the DNA.
c. UV rays could cause methylation and phosphorylation of the DNA bases which could become dimerized rendering no accessibility of DNA.
d. The UV rays can cause methylation and acetylation of histones making the DNA more tightly packed and leading to inaccessibility.

Key Concepts

Chromatin Structure

Chromatin structure refers to the organization and packaging of DNA around histone proteins. The degree of chromatin compaction is a key regulatory factor for gene expression. Open chromatin (euchromatin) is accessible to transcription factors and actively transcribed genes, whereas closed chromatin (heterochromatin) is less accessible, leading to gene silencing.

Histone Modifications

Histone modifications, which include acetylation, deacetylation, phosphorylation, and others, play a critical role in the regulation of chromatin structure and gene transcription. Acetylation generally opens up chromatin structure to enhance gene transcription, while deacetylation tends to condense chromatin, leading to reduced accessibility of transcriptional machinery.

Environmental Influence on Epigenetics

Environmental factors such as ultraviolet light exposure are capable of inducing epigenetic modifications. These external stimuli can trigger changes in the patterns of DNA methylation and histone modifications, thereby altering chromatin structure and consequently modifying gene expression. This mechanism illustrates how external conditions can have a lasting impact on cellular function and phenotype.

Epigenetic Modifications

Epigenetic modifications refer to heritable changes in gene expression that occur without altering the underlying DNA sequence. These modifications modulate how genes are turned on or off, affecting cellular function and identity. They include mechanisms such as DNA methylation and various histone modifications, which together govern the overall accessibility of the DNA within the cell nucleus.

DNA Methylation

DNA methylation involves the addition of a methyl group to the DNA molecule, typically at cytosine bases. This modification is commonly associated with gene repression, as the methyl groups can inhibit the binding of transcription factors and promote a more compact chromatin state, thereby limiting gene expression.

Transcript

00:01 How does uv radiation actually damage dna? so we all hear that we need to put sunscreen when we go out in the sun to protect our skin from the sun.

00:15 Why do we need to protect it? that's because dna has a very high affinity for absorbing uv radiation and the energy in the uv radiation can result in the dimerization of thymine nucleotides.

00:33 So suppose that you have two thymines next to each other.

00:36 So right here, this blue base here and this blue base here, they are both thymines on the same backbone of a dna chain.

00:47 And if you look at them a little more zoomed in, this is what they look like.

00:52 Okay? so you have one thymine here, another thymine here, and they are connected through a phosphodiacester bond, the phosphate that's in between nucleotide residues that helps make the backbone of the dna.

01:08 The uv radiation results in the dimerization of these two thymines.

01:14 So after uv damage, this is what it looks like.

01:18 And if you notice there, we have removed that phosphate.

01:21 We have removed that phosphodiaster bond.

01:24 And there is now actual covalent linkage between the two bases of the thymines.

01:33 So this dimerization of thymine changes the shape of the dna.

01:38 And in biology, form fits function.

01:42 So if you change the shape of something, you are going to change its function.

01:46 Same thing with dna.

01:48 Dna has a uniform structure throughout.

01:51 It maintains the same major, the same minor groove and the same diameter throughout the entire length of the dna...