Histone proteins can be modified through methlyation, acetylation, and phosphorylation. Most oftenit is lysine (K) amino acids that are modified. To investigate the role of the acetylation of a lysine atposition 56 (K56) in histone H3, a mutation was made where the lysine is replaced with an arginineresidue, which prevents acetylation. This mutation is lethal at the embryonic stage.a. What effect would this mutation have on the packing of chromatin? Explain your answer. (2marks)b. What could be the reason that this mutation is lethal? Suggest a reason and explain yourchoice. (3 marks)Questions continue over the page.
Question
Histone proteins can be modified through methlyation, acetylation, and phosphorylation. Most oftenit is lysine (K) amino acids that are modified. To investigate the role of the acetylation of a lysine atposition 56 (K56) in histone H3, a mutation was made where the lysine is replaced with an arginineresidue, which prevents acetylation. This mutation is lethal at the embryonic stage.a. What effect would this mutation have on the packing of chromatin? Explain your answer. (2marks)b. What could be the reason that this mutation is lethal? Suggest a reason and explain yourchoice. (3 marks)Questions continue over the page.
Solution
a. The mutation that replaces lysine with arginine at position 56 in histone H3 would likely result in tighter packing of chromatin. This is because acetylation of lysine residues generally reduces the positive charge of the histone proteins, weakening the interaction between the histones and the negatively charged DNA, thereby leading to a more relaxed chromatin structure. If acetylation is prevented, as in this case, the chromatin would remain in a more condensed state.
b. The mutation could be lethal because it may disrupt normal gene expression. The acetylation of histones is a key mechanism in the regulation of gene expression. When acetylation is prevented, genes that are normally activated by this modification may not be expressed. This could disrupt essential developmental processes, leading to lethality at the embryonic stage.
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What is the effect of high levels of histone acetylation on the expression of a gene?Group of answer choicesThis changes the splicing of the geneIt causes the chromatin to condenseThe gene becomes expressed lessThe gene becomes expressed more
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Affects of acetylation on histones (lysine)?Select your answer:Select your answerOPTION ALTERNATIVE Adding acetyl group to the end of the histone makes it negative makes the DNA that its associated with more readily transcribed Removes positive charge from the side-chain so weakens the interaction between histones and negatively charged DNA. All of the above
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What are the two types of Chromatin Modification? Describe each.
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