Final answer:
Contrary to what the first statement posits, cells do not always produce proteins from every gene, as gene expression is regulated. The second statement is true, more primers are indeed used in lagging strand synthesis. The final statement is false, as the genetic code has multiple codons encoding for some amino acids.
Step-by-step explanation:
The subject of this question pertains to DNA replication and protein synthesis in the field of biology. When tackling such true or false questions, it is important to consider the current understanding of molecular biology.
- True/False 29: Cells are always producing proteins from every gene they possess. This statement is false. Cells regulate gene expression and only produce proteins from certain genes as needed. The correct statement might be: Cells produce proteins from specific genes according to the cell's regulatory mechanisms and needs.
- True/False 30: More primers are used in lagging strand synthesis than in leading strand synthesis. This statement is true. The lagging strand is synthesized in short segments called Okazaki fragments, each requiring a primer, whereas the leading strand is synthesized continuously with a single primer.
- True/False 31: Each codon within the genetic code encodes a different amino acid. This statement is false. The genetic code is degenerate, which means that some amino acids are encoded by more than one codon.
Regarding the necessity of continuing the experiment of Meselson and Stahl for at least two rounds of replication after isotopic labeling with 15N, the requirement was to ensure the correct model of DNA replication could be distinguished. If they had stopped after only one round, it would have been impossible to rule out the conservative model of DNA replication, as both semi-conservative and conservative replication would yield one hybrid band of 15N/14N DNA. Two rounds confirmed the semi-conservative nature because resultant DNA had one band of 15N/14N and one band of pure 14N DNA.