I would say that the answer is C, since variations in crop restore the nitrogen in the soil from certain bacteria growing on the root of beans, including legumes.
Answer:
a. tryptophan levels are low.
Explanation:
Attenuation occurs when the tryptophan level in the cell is high so there is no need to synthesize tryptophan any more. In this situation, tryptophan mRNA synthesis comes to an end.
Attenuation is based on two following attributes:
(1) Translation dependent transcription
(2) Ability of RNA to assume alternative secondary structures.
Leader peptide is 16o nucleotide long region which contains 4 regions named as R1, R2, R3 and R4. In R1 region there are 2 tryptophan codons while after R4 region there is a polyU sequence. It it only after leader peptide, tryptophan biosynthesis genes are present in tryptophan operon.
When tryptophan levels in the cell are high, ribosome at R1 region immediately clears the region without any halt as a result of which R1 is able to pair up with R2 and R3 is able to pair up with R4 making a secondary structure i.e. hair pin structure. Soon after that there is a polyU sequence. This is a perfect condition for rho independent transcription termination.
This phenomenon helps in conserving the energy by inhibiting transcription in cell when tryptophan is not required because it is already present in abundance.
In contrast to this, when tryptophan levels are low, transcript is supposed to be transcribed so as to enhance the level of tryptophan in the cell. In such situation, the tRNA charged with tryptophan amino acid is in scarcity so the ribosome keeps waiting for this charged tRNA in R1. Since ribosome has occupied this region, R1 will be unable to pair up with R2. So R2 will pair up with R3. Since R3 has paired up with R2, it will not be able to pair up with R4. So a <u>secondary hair pin structure</u><u> </u><u>immediately followed up by polyU sequence will not form and hence transcription by RNA polymerase will go on. </u>
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<span>Reptiles that live on land convert the ammonia in their unrine to uric acid, which is much less toxic , so it doesn't need to be diluted as much. Also excess water is absorbed in the cloaca, reducing the urine to a paste and conserving water.</span>
Answer:
Prokaryote: lack of membrane-bound nucleus, DNA in cytoplasm, single circular chromosome
Eukaryote: Membrabe-bound nucleus, DNA inside nucleus, multiple chromosome.
Explanation:
Prokaryotes are one of the two domains, which consists of organisms that do not possess a membrane-bound nucleus. Due to this fact, the genetic material (DNA) of prokaryotic organisms like bacteria is found located in their cytoplasm. The DNA is found as a single circular chromosome in a region called NUCLEOID.
On the contrary, eukaryotes are the second domains of organism characterized by their possession of a membrane-bound nucleus that houses their genetic material (DNA). All the DNA of an eukaryotic organism like plants, animals etc. are found inside its NUCLEUS. They are made up of multiple linear chromosomes.