Answer:
B) Nitrogen-fixing bacteria and lightning
Explanation:
Nitrogen cycle is the natural process in which atmospheric nitrogen is converted into nitrite and nitrate with the help of bacteria.
Nitrogen cycle is directly dependent on nitrogen-fixing bacteria and lightning.
As bacteria are responsible for most of the chemical conversion in the nitrogen cycle such as nitrogen fixation (first step) is done by soil bacteria (Cyanobacteria) that form ammonia, which is toxic to plants; nitrification in which ammonia is converted into nitrites and nitrates with the help of Nitrobacter and denitrification bacteria involve Pseudomonas, and Achromobacter which convert nitrite and nitrate into nitrogen.
The lightning breaks nitrogen molecules and allow it to combine with oxygen in atmosphere which further dissolve in rain and form nitrates.
Hence, the nitrogen cycle is most directly dependent upon nitrogen-fixing bacteria and lightning and the correct option is B.
Answer:
The correct answer is- phosphorus and sulfur
Explanation:
Hershey and Chase used radioactive phosphorus and sulfur to label T2 bacteriophage. Then they infected E.coli with these bacteriophage labeled with radioactive phosphorus and sulfur.
After infection, they centrifuge the cell and found that radioactive phosphorus is present in the bottom and radioactive sulfur in supernatant . As sulfur is mostly the part of protein not DNA and is found in supernatant and phosphorus is mostly present in DNA not protein which was found in cell debris, therefore, it was proved that DNA is the genetic material.
Answer:
The correct answer is ''All of the choices are correct.''
Explanation:
Pregnant women are a risk group for listeriosis, the disease caused by the Listeria monocytogenes bacteria found in contaminated food. This organism can cross the placenta and affect the fetus. Due to the decrease in cellular immunity, pregnant women are part of the population at risk and are 17-20 times more likely to develop listeriosis after the consumption of contaminated food and it usually occurs from the third trimester and appears as a disease mild with not very high fever, joint and muscle pain. Listeriosis can cause miscarriages during the first three months of pregnancy. As the third trimester is reached, the mother is at greater risk. It presents a 40-50% fetal or neonatal mortality. In the first or second trimester it produces septic abortions and intrauterine fetal death, in the third trimester she produces chorioamnionitis and premature labor. In 1/3 cases it can occur asymptomatically in the fetus / neonate. In newborns, listeriosis can cause blood infections and meningitis.
Pleiotropy occurs when one gene influences multiple, seemingly unrelated phenotypic traits. A single gene is responsible for pigmentation and hearing.
bacteria are classified into 5 groups, spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes).
