1. The elucidation of the regulatory mechanisms associated with the enzymes of l

Question

1. The elucidation of the regulatory mechanisms associated with the enzymes of lactose utilization n E.coli was a landmark in our understanding of regulatory processes in microorganisms. In formulating the operon hypothesis as applied to the lactose system, the researchers, Jacob and Monod, found that results from particular merozygotes (partial diploid strains) were invaluable. Specifically, in terms of the operon hypothesis, what information did the merozygotes provide that the haploids could not? 2. The following figure shows the percentage of ribosomes engaged in translation in unfertilized sea urchin eggs (0 hr) and at various times after fertilization. In the unfertilized egg 25 3 4 Development Time (min) less than 1% of ribosomes are engaged in translation, while at 2 hr post-fertilization, about 20% of ribosomes are translating mRNA molecules. It is known that no new mRNA is made during the time period shown. How may this data be interpreted? 2

Explanation / Answer

1. The merozygotes provided the information about visiting and trans acting regulatory molecules on the operon. For example, let's say that the genome of the bacteria has a mutation in the repressor gene and thus cannot form a functional repressor. The other plasmid which makes the bacteria a partial diploid has a functional repressor gene which forms functional repressor which shows a trans binding as in it can bind the operator of both the operon and thus regulate both the operons.

2. Fertilization triggers a period of active synthesis in the egg. The mRNA produced are translated to proteins to support the growth and development of the zygote.

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