Answer:
D. Crossing over
Explanation:
During prophase-I of meiosis-I, a process of genetic recombination occurs. During this process, two non-sister chromatids of the paired homologous chromosomes exchange a part of the genetic segment. This is called crossing over. Crossing over results in the production of recombinant chromatids that carry new combinations of alleles that were otherwise not present in the parental chromosomes. Therefore, crossing over generates some extra combinations of alleles.
Answer:
A) A corepressor must be present
Explanation:
The key to operon expression lies in the sequence of the operator and the presence or absence of a repressor. When the repressor binds the operator, it prevents RNA polymerase from initiating transcription. The capability of the repressor to bind the operator and inhibit transcription depends on the conformation of the repressor, which is regulated allosterically by a key compound in the metabolic pathway, such as lactose or tryptophan. In a repressible operon, such as the tryptophan (or trp) operon, the repressor is unable to bind to the operator DNA by itself. Instead, the repressor is active as a DNA-binding protein only when complexed with a specific factor, such as tryptophan , which functions as a corepressor.
When tryptophan is plentiful, tryptophan molecules act as corepressors by binding to the (1) inactive repressor and (2) change its shape, allowing it to bind to the operator, (3) preventing transcription of the structural genes
The cell membrane allows this to be true
Millimeters are the answer here friend. hope you have a bugunga day!
(pronounced bu-gun-ga)