Question

DNA, Genes and Protein Synthesis Activity 13: Protein Synthesis is the process by which cells produce (synthesize) proteins. An overview of the process is shown in model 2 (below). Gone 2 Gene 1 Gene 3 DNA strand3 TRANSLATION Protein Trp Gly Model 2 ACTIVITY and QUESTIONS 1. Based on the information you can gather from model 1 complete the following sentences: a. The nucleotide Adenine (A) always pairs with the nucleotide b. The nucleotide Guanine (G) always pairs with the nucleotide . . 40 DNA, Genes,and Protein Synthesis Activity 13: 2. The bases that interact with each other are called complementary bases. this definition and your answers to 1 complete the following: a. Thiamine (T) is the complementary base of b. Cytosine (C) is the complementary base of c. Adenine (A) is the complementary base of d. Guanine (G) is the complementary base of Based on 3. Shown below is the nucleotide sequence for one strand of a stretch of DNA Write the nucleotide sequence of the complementary strand of DNA AGCTGACCTAGCGGACAA 4. Protein synthesis is a multi-step process (see model 2) First the genetic information contained in the DNA sequence is used to synthesize a new molecule of mRNA. Based on the information in model 2 answer the following: a. The process of synthesizing a mRNA strand is called b. In mRNA the complementary base of Adenine (A) is c. Write the mRNA strand that would be synthesized by the following DNA sequence: AGCT GACCTAGCGGACAA 41 Activity 13: DNA, Genes, and Protein Synthesis 5. During the second stage of protein synthesis the ribosome 'reads' (or decodes) the mRNA sequence to produce a specific polypeptide chain. Based on the information in model 2 answer the following: a. How may nucleotides on the mRNA strand codes for a single amino acid? b. The mRNA code that instructs for the placement of a specific amino acid is called a c. According to model 2 the codon for the amino acid tryptophan (Trp) is d. According to model 2 the codon for the amino acid serine (Ser) is e. How may codons are there in the mRNA strand you synthesized in step 4(c)? 6. his eu The table above lists the genetic code (or codons) for each of the 20 amino acids. Based on the information given in this table answer the following a. The codon for the amino acid Methionine Met) is b. The codon for the amino acid Leucine (Leu) is c. The codon CCC codes for the amino acid d. How many codon code for the amino acid Valine (Val)? e. How are the codons that code for Valine (identified above) different from one or 42

Answer 1

(1) The nucleotide adenine (A) always pairs with the nuecleotide thymine (T).

The nucleotide Guanine (G) always pairs with the nuecleotide cytosine (C).

(2) Thymine is a complementary base of adenine.

Cytosine is a complementary base of guanine.

Adenine is a complementary base of thymine.

Guanine is a complementary base of cytosine.

(3) The complementary strand of the given DNA strand is:

TCGACTGGATCGCCTGTT

(4) (i) The process of synthesizing mRNA strand is known as transcription.

(ii) In mRNA, the complementary base to adenine is Uracil (U).

(iii) The mRNA strand that would be synthesized by the given DNA strand is:

UCGACUGGAUCGCCUGUU

(5) (i) Three nucleotides of an mRNA code for an amino acid.

(ii) The mRNA code that instructs the placement of a specific amino acid is known as a codon.

(iii) The codon for Tryptophan is UGG.

(iv) The codon for amino acid serine is UCA.

(v) Total number of amino acids encoded by mRNA in step 4(c) = 18/3 = 6.

(6) (i) The codon for amino acid methionine is AUG.

(Ii) The codon for amino acid leucine is CUU or CUC.

(iii) The codon CCC codes for the amino acid proline.

(iv) Valine is encoded by four codons.

(v) The codons that code for valine differ in their last nucleotide of the codon.