Molecular Biology Techniques

Step 1: Understanding alcoholic beverage production.
Wine and beer are produced by fermentation of sugars using yeast.

Step 2: Identifying the missing step.
Distillation is used to produce spirits like whisky and rum, not wine or beer.

Step 3: Conclusion.
Therefore, wine and beer are produced without distillation.

Step 1: Understanding mycorrhiza.
Mycorrhiza is a mutualistic (symbiotic) association between the roots of plants and certain fungi, where both partners benefit.
Step 2: Benefits to both partners.
The fungal partner increases the surface area for absorption, helping the plant absorb water and minerals (especially phosphorus).
In return, the plant provides carbohydrates to the fungus.
Step 3: Analysis of options.
(A) Incorrect — coralloid roots of Cycas associate with cyanobacteria (Nostoc/Anabaena).
(B) Incorrect — leguminous plants associate with bacteria (Rhizobium), not fungi.
(C) Incorrect — grasses do not form mycorrhiza with bacteria.
(D) Correct — mycorrhiza is an association between roots of higher plants and fungi.
Step 4: Conclusion.
Mycorrhiza shows a symbiotic association between roots of higher plants and fungi.

Step 1: Understanding carbon source for plants.
Carbon is a major element required for the synthesis of carbohydrates and other organic molecules in plants.
Step 2: Primary source of carbon.
Terrestrial plants obtain carbon mainly from atmospheric carbon dioxide, which is fixed during the process of photosynthesis.
Step 3: Analysis of options.
(A) Incorrect — rocks are not a direct carbon source for plants.
(B) Incorrect — soil supplements do not provide carbon directly.
(C) Incorrect — soil CO\textsubscript{2} is negligible compared to atmospheric CO\textsubscript{2}.
(D) Correct — atmospheric CO\textsubscript{2} is fixed during photosynthesis.
Step 4: Conclusion.
On land, plants get carbon by fixation of atmospheric CO\textsubscript{2 during photosynthesis}.

Step 1: Understanding DNA polarity.
DNA strands have directionality due to the sugar-phosphate backbone. Each strand has a 5 end and a 3 end.
Step 2: Chemical groups at DNA ends.
At the 5 end of DNA, a free phosphate group is present, whereas the 3 end has a free hydroxyl (–OH) group.
Step 3: Analysis of options.
(A) oxygen: Incorrect. Oxygen is not present as a free terminal group.
(B) nitrogen: Incorrect. Nitrogen is part of nitrogenous bases, not terminal groups.
(C) phosphate: Correct. The 5 end carries a free phosphate group.
(D) hydroxyl: Incorrect. Hydroxyl group is present at the 3 end.

Step 1: Understanding Lac operon.
The Lac operon in {E. coli} controls lactose metabolism and includes genes lacZ, lacY, and lacA.
Step 2: Enzymes involved.
-galactosidase, permease, and transacetylase are products of Lac operon genes, while DNAase is unrelated to lactose metabolism.
Step 3: Conclusion.
Therefore, DNAase does not operate in the Lac operon.

Step 1: Understanding the DNA length.
For every 10 base pairs of DNA, the length of the DNA strand is approximately 34 Å (angstroms). Thus, for 44 base pairs, the length is calculated by multiplying 34 by 4.4, which gives 149.6 Å.
Step 2: Analyzing the options.
(A) 149.2 Å: This is incorrect, as it does not match the calculation for 44 base pairs.
(B) 149.3 Å: This is incorrect, it is very close but not the correct value.
(C) 149.4 Å: This is also incorrect, the correct value is 149.6 Å.
(D) 149.6 Å: Correct. This is the accurate length for a DNA segment with 44 base pairs. Step 3: Conclusion.
The correct answer is (D) 149.6 Å.

Step 1: Understanding mRNA.
Messenger RNA (mRNA) is the RNA that carries genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm, where polypeptides (proteins) are synthesized.
Step 2: Analyzing the options.
(A) r-RNA: Incorrect — Ribosomal RNA (rRNA) forms the core structure of the ribosome but does not carry the message for protein synthesis.
(B) r-DNA: Incorrect — rDNA refers to recombinant DNA, which is not involved in carrying messages for polypeptide formation.
(C) m-RNA: Correct — mRNA carries the genetic code for protein synthesis, which directs the formation of polypeptides.
(D) t-RNA: Incorrect — Transfer RNA (tRNA) helps in the translation process but does not carry the message for forming the polypeptide chain.
Step 3: Conclusion.
The correct answer is (C) m-RNA, as mRNA carries the genetic information for forming polypeptides.

Step 1: Understanding water potential.
Water potential is a measure of the potential energy of water in a system. The water potential of pure water at standard conditions (normal temperature and pressure) is considered zero.
Step 2: Analyzing the options.
(A) zero: Correct — The water potential of pure water is zero by definition.
(B) always more than one: Incorrect — Water potential is not greater than one in pure water.
(C) one: Incorrect — Water potential of pure water is zero, not one.
(D) less than one: Incorrect — Pure water has a water potential of zero, not less than one.
Step 3: Conclusion.
The correct answer is (A) zero, as pure water has a water potential of zero under standard conditions.