(b) the daughter strand is phosphorylated but the parent strand is not; (c) DNA polymerase is still attached to the parent strand;
(d) the parent strand has a 5' cap but the daughter strand does not;
(e) the Okazaki fragments of the daughter strand have not yet been ligated together. 6. Any of the following will result in a silent mutation EXCEPT___ _D _ (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.
7. The creation of a stop codon in the middle of a coding sequence within the gene is called a ___ _C _ a. missense mutation b. frameshift mutation c. nonsense mutation d. point mutation e. silent mutation
Regulation of gene expression:
1. Which of the following is NOT a feature of eukaryotic gene expression? ___ _C _ (a) polycistronic mRNAs are very rare;
(b) many genes are interrupted by non-coding DNA sequences;
(c) RNA synthesis and protein synthesis are coupled as in prokaryotes; (d) mRNA is often extensively modified before translation;
(e) multiple copies of nuclear genes, and pseudo genes can occur. 2. An operon（操纵子）consists of___ _B _ (a) All the genes for one biosynthetic pathway;
(b) A cluster of genes which are transcribed into a single mRNA; (c) Several ribosomes attached to the same mRNA molecule;
(d) The two nearby sequences on DNA where RNA polymerase binds; (e) The group of codons which all code for the same amino acid. 3. In positive regulation（正调控）___ _D _
(a) an activator protein binds DNA at a site called the operator; (b) a gene is always transcribed;
(c) constitutively expressed genes are turned off;
(d) an activator protein helps RNA polymerase bind the promoter; (e) none of the above is true.
4. Regulation（调控）of β-galactosidase（β-半乳糖苷酶）synthesis（合成）is___ _D _ (a) under neither positive nor negative control; (b) under only positive control;
(c) under only negative control; (d) under both positive and negative control.
5. In the presence of glucose（葡萄糖）and the absence of lactose（乳糖）___ _C _ Both the LacI 阻遏物 and the Crp protein will bind to the DNA; Neither LacI nor Crp protein will bind to the DNA;
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Crp protein will not bind to DNA but the LacI 阻遏物 will; Crp protein will bind to DNA but the LacI 阻遏物 will not.
6. Which of the following statements describes a step in the regulation of the lac operon___ A_ (a) A cyclic AMP-CAP complex binds to the CAP site;
(b) The 阻遏物 binds to CAP to form an inactive 阻遏物;
(c) Cyclic AMP competes with the 阻遏物 for binding to the operator;
(d) The 阻遏物 undergoes a conformational change upon binding cyclic AMP. 7. Antisense RNA（反义RNA）can regulate genes by binding to the___ _A _ (a) mRNA;
(b) Small subunit of the ribosome; (c) RNA polymerase; (d) 23s rRNA
(e) initiator tRNA.
8. Which of the following sites may be thousands of base pairs away from a promoter, yet regulate transcription? ___ _C _ (a)Operators; (b) initiators; (c) enhancers; (d) all of the above; (e) none of the above. 9. Regulatory sequences known as enhancers___ _C _ (a) are needed for transcription by RNA polymerase III but not by RNA polymerase II; (b) Encode the snRNA molecules needed for splicing RNA; (c) May be located upstream or downstream of the promoter;
(d) Are where RNA polymerase first binds when it transcribes a gene;
Transposons:
1. At the two ends of an insertion sequence（插入序列）you would expect to find___ _A _ (a) Inverted repeats;
(b) Single stranded overhangs generated by restriction enzymes; (c) GC rich regions whose melting temperature is higher; (d) Short segments of RNA;
(e) Short tandem repeats of about 6 base pairs
2. DNA sequences that on rare occasions（低频率）move from one place in the genome to another are called ___ _C _ a. movers b. jumpons c. transposons d. transpodons e. jumposons
Techniques in molecular biology:
1. Which statement is NOT true about nucleic acid hybridization（杂交）? ___ _B _ (a) it depends on complementary base pairing;
(b) a polysaccharide can hybridize with a DNA strand ; (c) a DNA strand can hybridize with another DNA strand; (d) an RNA strand can hybridize with a DNA strand;
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