Answer:
The gene for beta-galactosidase turns off.
Explanation:
The gene that codifies the beta-galactosidase enzyme is part of the <em>lac</em> operon, which also contains two other genes that produce enzymes involved in the metabolization of lactose.
Between glucose and lactose, the bacteria will preferentially use glucose as an energy source. On the other hand, lactose is a dimer, and thus a series of enzymes are needed to process lactose before its use as an energy source.
If there is no lactose present, the genes contained inside this operon are turned off (the operon is repressed).
Spongy bone has trabecular which serve as reinforcing plates against a force. The loss of spongy bones causes weakening of the internal support that the compact bone requires and the entire bone breaks.
This biome has a layer of soil that can either be sandy, gravelly, or stony, depending on the type of desert. Deserts usually get at most 50 centimeters (20 inches) of rainfall a year, and the organisms that live in deserts are adapted to this extremely dry climate. Plants in deserts have adaptations to conserve water.
Consuming excessive amounts of pure water creates hypotonic environment in the body fluid surrounding the cell.
<h3>
What is a hypotonic solution?</h3>
- A solution having lower osmotic pressure than the solution to which it is compared.
- It has lower amount of solute (high amount of solvent) compared to other solution separated by a semi-permeable membrane.
- After consuming excessive amounts of pure water, the body fluid becomes hypotonic, so water enters from body fluid to the cell resulting in the cell to swell or break.
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Hello. This question is incomplete. The full question is:
"You determine that you have only 3 copies left of an important DNA fragment, so you decide to amplify it. Using flanking primers, how many PCR cycles would you have to run to generate over one billion (10^9) copies of the fragment?
"
Answer:
Approximately 29 cycles of PCR would be required.
Explanation:
As you may already know, PCR is a technique used in molecular biology that allows part of a DNA molecule to be recycled into millions of copies.
PCR allows this replication to be done through cycles. Each PCR cycle lasts about 2 minutes and allows the DNA molecule to undergo the separation of the strands, the binding of the primers and the synthesis of new DNA strands through DNA polymerase. This cycle is usually repeated 32 times, but this number may change depending on the number of copies the researcher thinks is necessary.
In this case, if a researcher wants 10 ^ 9 copies of DNA, he must do the following calculation to find the number of PCR cycles needed:
32 ^ x = 10 ^ 9
x = 28.3 = approximately 29 cycles.
