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Ch. 19 - Epigenetics
Chapter 18, Problem 23

Amino acids are classified as positively charged, negatively charged, or electrically neutral.

How does this property of lysine allow it to interact with DNA?

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Lysine is an amino acid with a side chain that contains an amino group, which is positively charged at physiological pH.
DNA is composed of nucleotides, each containing a phosphate group that is negatively charged.
The positive charge on lysine's side chain allows it to form electrostatic interactions with the negatively charged phosphate groups of DNA.
These interactions help stabilize the structure of DNA and can influence the binding of proteins to DNA.
This property of lysine is crucial in the context of histone proteins, which are rich in lysine and play a key role in DNA packaging within the cell nucleus.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Amino Acid Classification

Amino acids are organic compounds that serve as the building blocks of proteins. They can be classified based on their side chains into three categories: positively charged (basic), negatively charged (acidic), and electrically neutral. This classification affects their interactions with other molecules, including nucleic acids like DNA.
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Lysine's Positive Charge

Lysine is an amino acid that carries a positive charge at physiological pH due to its amino group. This positive charge allows lysine to form ionic bonds with negatively charged molecules, such as the phosphate backbone of DNA. Such interactions are crucial for stabilizing protein-DNA complexes and facilitating processes like transcription and replication.
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Positional Cloning

DNA Structure and Charge

DNA is a negatively charged molecule primarily due to its phosphate groups. The negative charge of DNA plays a significant role in its interactions with positively charged amino acids like lysine. Understanding this charge interaction is essential for grasping how proteins bind to DNA and regulate gene expression.
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DNA Structure
Related Practice
Textbook Question

From the data in Table 19.3, draw up a list of histone H3 modifications associated with gene activation. Then draw up a list of H3 modifications associated with repression.

Are these overlaps explained by different modifications?

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Textbook Question

From the data in Table 19.3, draw up a list of histone H3 modifications associated with gene activation. Then draw up a list of H3 modifications associated with repression.

If not, how can you reconcile these differences?

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Textbook Question

Amino acids are classified as positively charged, negatively charged, or electrically neutral.

Which category includes lysine?

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Textbook Question

Amino acids are classified as positively charged, negatively charged, or electrically neutral.

How does acetylation of lysine affect its interaction with DNA, and how is this related to the activation of gene expression?

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Textbook Question

A particular type of anemia in humans, called β-thalassemia, results from a severe reduction or absence of the normal β-globin chain of hemoglobin. However, the γ-globin chain, normally only expressed during fetal development, can functionally substitute for β-globin. A variety of studies have explored the use of the nucleoside 5-azacytidine for the expression of γ-globin in adult patients with β-thalassemia.

Explain why this drug may also have some adverse side effects.

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Textbook Question

A particular type of anemia in humans, called β-thalassemia, results from a severe reduction or absence of the normal β-globin chain of hemoglobin. However, the γ-globin chain, normally only expressed during fetal development, can functionally substitute for β-globin. A variety of studies have explored the use of the nucleoside 5-azacytidine for the expression of γ-globin in adult patients with β-thalassemia.

How might 5-azacytidine lead to expression of γ-globin in adult patients?

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