Question

3 dna, rna, and protein (continued)
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1. summarize the process by which the dna code is made into a protein

1. describe the function of each of the following in protein synthesis: rrna, mrna, and trna.

1. explain why scientists concluded that the instructions for species characteristics were carried in dna.

1. explain the role of rna polymerase in mrna synthesis.

1. conclude why beadle and tatum’s “one gene, one enzyme” hypothesis has been modified since they presented it in the 1940s.

1. if the genetic code used four bases as a code instead of three, how many code units could be encoded?

Explanation:

1. The process of DNA to protein is protein synthesis, including transcription (DNA → mRNA) and translation (mRNA → protein).
2. rRNA forms ribosomes (protein synthesis site); mRNA carries DNA’s protein code; tRNA delivers amino acids to ribosomes.
3. Experiments (e.g., Avery-MacLeod-McCarty, Hershey-Chase) showed DNA transfers traits, not protein.
4. RNA polymerase synthesizes mRNA by transcribing DNA’s gene sequence.
5. Later discoveries: one gene makes non-enzyme proteins, or multiple polypeptides via alternative splicing.
6. Genetic code uses 4 bases; 4-base codons: \(4^4 = 256\) code units.

Answer:

1. Protein synthesis has two steps: transcription (DNA → mRNA) and translation (mRNA → protein).
2. rRNA: Forms ribosomes (protein synthesis site); mRNA: Carries DNA’s protein blueprint; tRNA: Transfers amino acids to ribosomes.
3. Experiments (Avery-MacLeod-McCarty, Hershey-Chase) proved DNA (not protein) transmits genetic traits.
4. RNA polymerase catalyzes mRNA synthesis by transcribing DNA’s gene sequence.
5. Updates: Genes encode non-enzyme proteins; alternative splicing makes multiple polypeptides from one gene.
6. 256