Eukaryotic Chromatin

Flashcards about Eukaryotic Chromatin Compaction

What is Eukaryotic Chromosomes composed of?

Each set is composed of several different linear chromosomes

What does a eukaryotic chromosome contain?

Origins of replication, Centromere, Kinetochore proteins, Telomere

What is Telomere's function?

Prevent translocations and are necessary for maintenance of chromosome length

Where are Eukaryotic Genes located?

Located between the centromeric and telomeric regions along the entire chromosome

What are Unique or non-repetitive sequences?

Found once or a few times in the genome and includes structural genes as well as introns and other noncoding DNA

What are Moderately repetitive sequences?

Found a few hundred to a few thousand times and includes Genes for rRNA and Transposable elements

What are Highly repetitive sequences?

Found tens of thousands to millions of times

What is Chromatin?

DNA-protein complex in eukaryotes

What is a Nucleosome composed of?

Composed of double-stranded DNA wrapped around an octamer of histone proteins

What are the four different histones in a octamer?

H2A, H2B, H3, and H4

What positively-charged amino acids do Histone proteins contain?

Lysine and arginine

Which is the linker Histone?

H1

What do Linker histones do?

Play a role in the organization and compaction of the chromosome

What does Nucleosomes Join to Form?

Associate with each other to form a more compact structure – the 30-nm fiber

What are Radial Loop Domains?

Matrix-attachment regions (MARs) also known as Scaffold-attachment regions (SARs)

What is Euchromatin?

Less condensed regions of chromosomes, Transcriptionally active

What is Heterochromatin?

Tightly compacted regions of chromosomes, Transcriptionally inactive (in general)

Name some Histone modifications

Methylation, Acetylation, Ubiquitination, Phosphorylation, Citrullination

What benefits do eukaryotic organisms derive from gene regulation?

Respond to changing environmental conditions and Express only those proteins needed at particular times in life and cell cycle

What are the two main types of Transcription factors?

General transcription factors and Regulatory transcription factors

Regulatory transcription factors

Activators and Repressors

What is an Activator?

A regulatory protein that increases the rate of transcription

What is a Repressor?

is a regulatory protein that decreases the rate of transcription

What does the binding of a transcription factor to an Enhancer do?

Increases the rate of transcription

What does the binding of a transcription factor to an Silencer do?

Decreases the rate of transcription

What are Epigenetic Mechanisms for Gene Regulation?

Histone Variants, Histone Code, Nucleosome Positioning, DNA Methylation

What are ways Histones can be modified?

Acetylation, Methylation, Phosphorylation

What does ATP do in the ATP-dependent modification of chromatin?

Reposition nucleosomes, Remove nucleosomes, Change composition of nucleosomes

What happens in DNA Methylation?

Methyl group added to a cytosine

Methylation results in:

Proteins binding to the methylated cytosine and inhibiting transcription and A chromatin structure that silences gene expression

What is Epigenetics?

Change in gene expression not based on the DNA sequence itself, Long-term maintenance of the change in expression, Passed from cell to cell, and May be passed from generation to generation

DNA methylation

Methyl groups may be attached to cytosine bases in DNA. When methylation occurs near promoters, transcription is usually inhibited.

Chromatin remodeling

Nucleosomes may be moved to new positions or evicted. When such changes occur in the vicinity of promoters, the level of transcription may be altered.

Covalent histone modification

Specific amino acid side chains found in the aminoterminal tails of histones can be covalently modified.

Localization of histone variants

Histone variants may become localized to specific positions, such as near the promoters of genes, and affect transcription.