题目

2.某β地贫病人,其编码β链第39位氨基酸(谷氨酰胺)的密码子(CAG)经碱基替换后变成终止密码(UAG),导致新合成的珠蛋白β链由正常的146个氨基酸残基变为只有38个氨基酸肽链,这类突变属于() In a ß-degenerate patient, the codon (CAG) encoding the 39th amino acid of the ß-chain (glutamine) was changed to a stop codon (UAG) by base substitution, resulting in the newly synthesized ß-chain of the bead protein being changed from the normal 146 amino acid residues to a peptide chain of 38 amino acids only, and this type of mutation belongs to the group of mutations(). A 错义突变missense mutation B 移码突变Code shift mutation C 无义突变Nossense mutation D 终止密码突变stop codon mutation

2.某β地贫病人,其编码β链第39位氨基酸(谷氨酰胺)的密码子(CAG)经碱基替换后变成终止密码(UAG),导致新合成的珠蛋白β链由正常的146个氨基酸残基变为只有38个氨基酸肽链,这类突变属于() In a ß-degenerate patient, the codon (CAG) encoding the 39th amino acid of the ß-chain (glutamine) was changed to a stop codon (UAG) by base substitution, resulting in the newly synthesized ß-chain of the bead protein being changed from the normal 146 amino acid residues to a peptide chain of 38 amino acids only, and this type of mutation belongs to the group of mutations(). A 错义突变missense mutation B 移码突变Code shift mutation C 无义突变Nossense mutation D 终止密码突变stop codon mutation

题目解答

答案

C

解析

步骤 1：理解突变类型
突变类型包括错义突变、移码突变、无义突变和终止密码突变。错义突变是指密码子改变导致氨基酸改变，但肽链长度不变；移码突变是指插入或删除碱基导致读码框改变，影响后续氨基酸序列；无义突变是指密码子改变为终止密码子，导致肽链提前终止；终止密码突变是指终止密码子改变为编码氨基酸的密码子，导致肽链延长。

步骤 2：分析题目中的突变
题目中提到，编码β链第39位氨基酸（谷氨酰胺）的密码子（CAG）经碱基替换后变成终止密码（UAG），导致新合成的珠蛋白β链由正常的146个氨基酸残基变为只有38个氨基酸肽链。这表明突变导致肽链提前终止，符合无义突变的定义。

步骤 3：确定突变类型
根据上述分析，题目中的突变属于无义突变。