Histone Variants and Modifications Quiz
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Questions and Answers

Histone variants can have an impact on gene transcription when located near the promoter.

True

Covalent histone modifications include only acetylation and phosphorylation.

False

Histone acetylation causes the DNA to wrap more tightly around the histones.

False

Over 50 enzymes that modify histones have been identified in humans.

<p>True</p> Signup and view all the answers

DNA methylation generally promotes transcription when it occurs near promoters.

<p>False</p> Signup and view all the answers

Covalent histone modifications can alter the level of transcription by affecting nucleosome interactions.

<p>True</p> Signup and view all the answers

Gene expression is the process by which information within a gene is used to produce a functional product.

<p>True</p> Signup and view all the answers

Epigenetic regulation involves irreversible changes in gene expression.

<p>False</p> Signup and view all the answers

Transcriptional regulation only ensures that transcription occurs but does not affect the extent of transcription.

<p>False</p> Signup and view all the answers

Post-transcriptional regulation involves controlling gene expression at the RNA level.

<p>True</p> Signup and view all the answers

The central dogma of molecular biology describes the flow of information from RNA to protein.

<p>False</p> Signup and view all the answers

Translational regulation involves controlling the rate at which transcription occurs.

<p>False</p> Signup and view all the answers

Repressors and activators are examples of factors involved in translational regulation.

<p>False</p> Signup and view all the answers

Gene expression is completely independent of environmental factors.

<p>False</p> Signup and view all the answers

Methylation near the promoter generally increases the level of transcription.

<p>False</p> Signup and view all the answers

Euchromatin is transcriptionally active due to its less condensed structure.

<p>True</p> Signup and view all the answers

Facultative heterochromatin remains in the same form across all cell types.

<p>False</p> Signup and view all the answers

HP1 (heterochromatin protein 1) contributes to the compaction of nucleosomes.

<p>True</p> Signup and view all the answers

Heterochromatin patterns are established only after embryonic development.

<p>False</p> Signup and view all the answers

Chromatin remodeling can involve the rearrangement of nucleosomes.

<p>True</p> Signup and view all the answers

Post-translational regulation involves controlling the activity of proteins.

<p>True</p> Signup and view all the answers

Non-coding RNAs are responsible for encoding proteins.

<p>False</p> Signup and view all the answers

Epigenetic regulation leads to irreversible changes in gene expression.

<p>False</p> Signup and view all the answers

DNA methylation usually promotes gene transcription.

<p>False</p> Signup and view all the answers

Hemimethylated DNA refers to DNA that is partially methylated.

<p>True</p> Signup and view all the answers

DNA methyltransferase is responsible for the removal of methyl groups from DNA.

<p>False</p> Signup and view all the answers

Covalent modifications are an example of post-translational regulation.

<p>True</p> Signup and view all the answers

Chromatin remodeling involves changes to the structure of proteins after translation.

<p>False</p> Signup and view all the answers

Methylation near promoter sites may impact the process of transcription.

<p>True</p> Signup and view all the answers

Covalent histone modification does not affect gene expression.

<p>False</p> Signup and view all the answers

Study Notes

Histone Variants

  • Histone variants can change the structure of chromatin
  • There are five main types of histones: H1, H2A, H2B, H3, and H4
  • Histone variants are modified histone genes that have accumulated mutations that alter the amino acid sequence
  • Histone variants are found in specific regions of the genome, such as the promoter

Covalent Histone Modifications

  • Over 50 enzymes identified in mammals can modify the amino-terminal tails of histones
  • Common modifications include: acetylation (COCH3), methylation (CH3), and phosphorylation (phosphate groups)
  • Covalent histone modification affects the level of transcription by influencing interactions within nucleosomes
  • Acetylation loosens the DNA around histones, making it more accessible to transcription factors, thereby increasing transcription

Chromatin Remodeling

  • Involves changing the structure of the chromosome by moving, removing, or rearranging nucleosomes
  • Chromatin is divided into heterochromatin (tightly compacted, transcriptionally inactive) and euchromatin (less condensed, transcriptionally active)
  • Facultative heterochromatin is able to switch between euchromatin and heterochromatin
  • Heterochromatin can bind to the nuclear lamina
  • Patterns in chromatin can be passed to daughter cells
  • Heterochromatin patterns are established during embryonic development
    • Constitutive heterochromatin – the same in all cell types
    • Facultative heterochromatin – cell-specific

DNA Methylation

  • Involves the covalent attachment of methyl groups (-CH3) to cytosine bases in DNA
  • Methylation is carried out by DNA methyltransferases
  • Methylation typically inhibits gene transcription, particularly near promoters
  • DNA methylation is heritable
    • Unmethylated regions of DNA can be methylated by de novo methylation
    • Hemimethylated DNA can be fully methylated through maintenance methylation

Epigenetic Regulation

  • Epigenetic changes are heritable, reversible, and happen without changes in the DNA sequence
  • Play a role in development (change throughout an organism's life) and can be impacted by the environment
  • Major types of epigenetic regulation include:
    • DNA methylation
    • Chromatin remodeling
    • Covalent histone modification
    • Localization of histone variants

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Description

Test your knowledge on histone variants, their modifications, and the role they play in chromatin remodeling. This quiz covers important concepts including histone types, covalent modifications like acetylation and methylation, and how these processes influence gene transcription. Dive into the intricate world of epigenetics and chromatin biology!

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