二、选择题：
1. All of the following are features of eukaryotic but not prokaryotic genetic systems EXCEPT: （ ）
a) Transcription and translation are coupled.
b) Export of spliced mRNAs.
c) Only monocistronic mRNAs.
d) "Junk" DNA. e) Compartmentalization
2. Nuclear mRNA splicing is performed（ ）
a). in nucleosomes
b). in spliceosomes
c). in the nucleolus
d). by RNA only
e). b and c
3. Which of the following statements regarding introns is FALSE? （ ）
a) Absolutely no bacteria have genes with introns.
b) Introns are usually transcribed but not translated.
c) Introns can be removed either through self-splicing or enzyme-mediated splicing.
d) In some circumstances, introns are retained in the mature mRNA.
e) Introns are removed from the primary transcript while it is still in the nucleus
4. Which of the following statements is true? （ ）
a) Exons are translated but not transcribed.
b) Exons are replicated but introns are not.
c) Both exons and introns are translated.
d) Introns are transcribed but not translated.
e) Exons are transcribed but not translated.
5. Any of the following will result in a silent mutation EXCEPT：（ ）
a) a mutation that occurs in a non-coding region.
b) a mutation that occurs in a non-regulatory region.
c) a mutation in which the third base of a codon is changed but the codon still codes for the same amino acid.
d) a mutation that occurs in the splice junction of an intron e) a mutation that occurs in an intron but not at the splice junction and branch site.
6. In Group II and nuclear mRNA splicing the first step is executed by（ ）
a). GTP
b). ATP
c). an internal A
d). H20
7. The Cap and Tail of eukaryotic messenger RNA consist of the following: （ ）
a) The Cap consists of the sequence AAAUAA added at the 5'-end
b) The Cap contains a single guanine nucleotide and the tail contains many methylated adenosine nucleotides
c) The Cap contains a single methylated guanine nucleotide and the tail contains many adenosine nucleotides
d) The Tail consists of a long sequence of A's added at the 5'-end
e) The Cap consists of a single guanine nucleotide added at the 3'-end
8. RNA editing sites in trypanosome mitochondria are selected by（ ）
a). complementary DNAs
b). RNA secondary structure
c). conserved sequences flanking the editing sites
d). guide RNAs
e). none of the above
9. Editing of the apolipoprotein B mRNA in mammals involves: （ ）
a). addition of Us
b). deletion of Us
c). conversion of C to U
d). conversion of U to C
10. The primary RNA transcript of the chicken ovalbumin gene is 7700 nucleotides long, but the mature mRNA that is translated on the ribosome is 1872 nucleotides long. This size difference occurs primarily as a result of: （ ）
a). capping
b). cleavage of polycistronic mRNA
c). removal of poly A tails
d). reverse transcription
e). splicing
三、填空题：
1.RNA是由核糖核苷酸通过 键连接而成的一种 。几乎所有的 RNA都是由 DNA 而来，因此，序列和其中一条链 。
2.多数类型的RNA是由加工 产生的，真核生物前体tRNA的 包
括 的切除和 的拼接。随着 和 端的序列切除，3’端加上了序列 。在四膜虫中，前体tRNA 的切除和 的拼接是通过 机制进行的。
