Protein synthesis worksheet
DNA (Strand 1) / T G T / ______/ ______DNA (strand 2) / ______/ C ______/ ______
mRNA (from strand 2) / ______/ ____ C A / ______
tRNA anticodons / ______/ ______/ G C A
2. Using a codon chart, name in order, the amino acids formed in question l.: ______
3. Suppose that you provide an actively dividing culture of E. coli bacteria with radioactive thymine. What would you expect to happen if a cell replicated its DNA and divided once in the presence of the radioactive base?
a. one of the daughter cells, but not the other, would have radioactive DNA
b. Neither daughter cell would have radioactive DNA
c. All four bases of the DNA would be radioactive
d. Radioactive thymine would pair with nonradioactive guanine.
e. DNA in both daughter cells would be radioactive
4. Which one of the following statements best describes the replication of DNA?
a. the double helix is cleaved at the phosphate bonds and new nucleotides pair with the appropriate sugars.
b. the hydrogen bonds between the bases are broken and new nucleotides pair with complementary bases on the old strands
c. the hydrogen bonds between the bases are broken and these bases are replaced by new bases
d. New bases are added at the 5' carbon on the sugar so that DNA synthesis occurs in a 3' to 5' direction
e. DNA is cleaved by DNA polymerases and new nucleotides are assembled by ligases
5. Which one of the following statements is false?
a. the nucleolus is a specialized region of a chromosome where tRNA is synthesized.
b. in base substitution mutations only a single nucleotide of a gene is altered.
c. molecules of mRNA are synthesized on the ribsomes from nucleotides brought by tRNA
d. some amino acids are specified by several "synonymous" codes
6. Though a gene codes ultimately for all aspects of a protein's structure, it codes directly only for:
a. primary structure b. secondary structure c. tertiary structure d. quaternary structure
5' AUGCCCUACUAC 3'
7. The sequence of the template strand of DNA of the gene that codes for the above message will be (assume 3' end is at left side in the answers)
a. AUGCCCAACUAC b. TACGGGATGATG c. UTGCCCUUCTACd. UACGGGUUGAUG e. ATGCCCTACTAC
8. The anticodon in the tRNA that attaches to the first codon will be:
a. UAC b. TAC c. AUG d. GUA e. ATG
9. The protein coded for by this message will have _____ amino acids
a. l b. 3 c. 4 d. 5 e. l2
l0. The second amino acid in the polypeptide chain will be (use codon chart)
a. lysine b. proline c. glycine d. aspartic acid e. phenylalanine
11. Transfer RNA functions in
a. carrying RNA from the ribosomes to mRNAb. attaching RNA to the ribosomes
c. joining proteins to form the ribosomes d. carrying mRNA from the nucleus to the cytoplasm
e. carrying amino acids to the correct site on mRNA
l2. As proteins are being synthesized, tRNA molecules are constantly being released from the site of amino acid incorporation. What happens to these tRNA molecules?
a. they return to the nucleus and bind to DNA again
b. they are used to code for synthesis of a protein
c. they immediately bind ot another mRNA
d. they pick up another amino acid of the same type that they had before
e. they pick up an amino acid of another type, specifically the amino acid coded for by the codon next to the one to which they originally bound
l3. The direction of transfer of genetic information in most living things is
a. proteinDNAmRNAb. DNAmRNAproteinc. DNAtRNAprotein
d. proteintRNADNAe. RNADNAmRNAprotein
l4 A certain gene codes for a polypeptide that is l26 amino acids long. The portion of the gene that codes for this polypeptide is probably how many nucleotides long?
a. 42 b. l26 c. 352 d. 378 e. 504
/ l5.The diagram represents tRNA which recognizes and binds a particular amino acid (in this case, alanine). Which one of the following triplets of bases on the DNA strand, or template, codes for this amino acid?a. GCC
b. CCG
c. CGG
d. ACC
e. CAT
l6. Suppose a gene has the DNA nucleotide sequence : ATA CCG CAT TAC TCA (no real gene could be this short, but for our purposes this will suffice) Which one of the following mutations would probably produce the greatest change in the activity of the protein for which this gene codes?
a. substitution of A for G in position 3b. deletion of the C at position 5
c. deletion of the A at position 15 d. addition of a G between positions l4 and l5
17. According to current ideas about the DNA genetic code, which one of the following statements is false?
a. the codon is 3 nucleotides longb. Every possible triplet codes for some amino acid c. the code is redundant (ie. it contains "synonyms")
d. the code is read in a regular sequence, beginning at the 5' end.e. the code is nonoverlapping
Questions l8-20 refer to the following segment of the base sequence of a gene:
3' ACGTGCCCGGAT 5'
l8. How many amino acids would the polypeptide encoded by this gene segment have?
a. l b. 3 c. 4 d. l2 e. 36
l9. The second codon on the mRNA derived from the segment will be:
a. TAC b. ACG c. ATG d. CAC e. UGC
20. The anticodon of the tRNA for the first codon will be
a. TCG b. ACG c. TCG d. UGC e GCA
21. Draw a diagram that illustrates the Central Dogma of Molecular Biology
22. Fill the chart below
DNA Triplet 3’5’ / mRNA codon 5’3’ / tRNA anticodon 3’5’ / Amino acidmethionine
GGA
TTC
UAG
AAA
23. Compare and contrast DNA and RNA
24. How are the ends of mRNA altered?
25. Why are they altered?
26. What is the difference between an intron and an exon?
27. List some reasons why we might have introns?
28. How do the existence of ribozymes render the statement “All biological catalysts are proteins.” Obsolete?
29. How do the existence of ribozymes call into questions the “one gene-one polypeptide” theory.
30. What is wobble?
31. Why is an insertion or deletion mutation usually more significant than a substitution mutation?
32. What’s the difference between missense and nonsense?