Question

21. The initiation of transcription of a gene occurs DNA when RNA polymerase binds to the of the gene b. start codon c. exon 1 d. intron 1 e. splice site 22. Phosphodiester linkages are present in a. DNA b. mRNA c. tRNA d a and b e. all of the above 23. The 5' cap and poly A tail are added to a. pre-mRNA in the cytoplasm b. help with pre-mRNA splicing. c. protect mRNA d. assist in posttranslation e all of the above 24. The genetic code is best described as a. degenerate but not ambiguous. b. ambiguous but not degenerate. c. both ambiguous and degenerate. d. neither ambiguous nor degenerate. e. degenerate in prokaryotes, but ambiguous in eukaryotes. of the anticodon, and helps explain why the end of 25. The wobble phenomenon occurs at codon shows the most redundancy a. the 5' end; 3' b. the 3' end; 5 c. the 3' end; 3 d. the 5' end; 5 e, either end; 5' 26. Which of the following would be an example of an unambiguous genetic code? a. One with 61 codons for 20 amino acids b. One in which UUU only code for phenylalanine c. One in which CCU could code for either alanine or leucine d. All of the above e. None of the above

Answer 1

21. a. promoter

The RNA polymerase binds to the promoter region of the DNA.

22. e. all of the above

A phosphodiester bond is the linkage between the 3' carbon atom of one sugar molecule and the 5' carbon atom of another, deoxyribose in DNA and ribose in RNA.

23. c. protect mRNA

During pre-mRNA processing, a 7-methylguanosine cap is added to the 5′ end and a string of approximately 200 A nucleotides, called the poly (A) tail, is added to the 3′ end of the pre-mRNA. These protect the mRNA from degradation, aid in the export of the mature mRNA to the cytoplasm, and help in initiating translation.

24. a. degenerate but not ambiguous

The genetic code is degenerate (more than one codon may specify a particular amino acid) but not ambiguous (no codon specifies more than one amino acid)

25. c. the 3' end: 3'

26. b. One in which UUU only code for phenylalanine