Organic Farming Practices Quiz

Molecular Basis of Inheritance

• Nucleic acids (DNA and RNA) are the fundamental building blocks of genetic material.
• DNA is the genetic material in most organisms.
• RNA is the genetic material in some viruses.
• RNA primarily acts as a messenger.

The DNA Nucleotide Chain

• Polynucleotides are polymers composed of nucleotides.
• DNA and RNA are both polynucleotides.
• A nucleotide comprises three components: a pentose sugar (ribose in RNA, deoxyribose in DNA), a nitrogenous base, and a phosphate group.
• Purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil) are the nitrogenous bases.
• Thymine is exclusive to DNA, while uracil is exclusive to RNA.

Structure of Polynucleotide Chain

• A nitrogenous base is linked to the pentose sugar via an N-glycosidic bond.
• Nucleosides are formed when a nitrogenous base is linked to a pentose sugar.
• Nucleotides are formed when a nucleoside is linked to a phosphate group.
• In RNA, each nucleotide has an additional -OH group at the 2' position of the ribose.
• Nucleotides are linked via phosphodiester bonds to form a polynucleotide chain.
• DNA is composed of two polynucleotide backbones coiled in a right-handed helix.
• The two chains are antiparallel, meaning one runs 5' to 3' and the other 3' to 5'.
• The bases project inward.

DNA Structure

• DNA is composed of two polynucleotide chains coiled into a right-handed double helix.
• The pitch of the helix is 3.4 nm (or 34 Å).
• There are 10 base pairs per helix turn.
• The distance between adjacent base pairs is 0.34 nm (or 3.4 Å).
• The bases in each strand are paired via hydrogen bonds: A with T (2 hydrogen bonds) and G with C (3 hydrogen bonds).

Chargaff's Rule

• In DNA, the proportion of adenine is equal to thymine, and the proportion of guanine is equal to cytosine.
• [A] + [G] = [T] + [C], or [A] + [G] / [T] + [C] = 1

DNA Length

• The length of a DNA molecule is determined by the number of base pairs multiplied by the distance between adjacent base pairs.
• For example, a human genome containing 6.6 billion base pairs would have a length of approximately 2.2 meters.
• The number of base pairs varies among different organisms.

Packaging of DNA

• In prokaryotes, DNA is packaged into a nucleoid structure.
• In eukaryotes, DNA is wrapped around histone proteins forming nucleosomes, which are further organized into chromatin fibers.

The Search for Genetic Material

• Griffith's experiment demonstrated a transforming principle.
• Avery, MacLeod, and McCarty identified DNA as the transforming principle.
• Hershey and Chase's experiment confirmed DNA as the genetic material.

Properties of Genetic Material

• A genetic material must exhibit self-replication.
• A genetic material must be chemically stable.
• A genetic material must be capable of mutations.
• RNA is more mutable than DNA.
• DNA is more stable than RNA.
• DNA is better for storing genetic information due to its stability, while RNA is more effective for conveying genetic information because it can directly code for protein synthesis.

RNA World

• RNA was likely the primary genetic material before DNA.
• RNA exhibits both catalytic and informational roles.

Central Dogma of Molecular Biology

• The central dogma describes the flow of genetic information from DNA to RNA to protein.
• In some viruses, there is reverse transcription, from RNA to DNA.
• This process is crucial in retroviruses like HIV.

DNA Replication

• Replication is the copying of DNA for cell division. The model for replication is semi-conservative.
• It occurs at a point called an origin. A unit of replication with one origin is called a replicon.
• DNA unwinds to form a Y-shaped replication fork, with two strands acting as templates.
• New strands are synthesized in the 5' to 3' direction via DNA polymerase using deoxyribonucleoside triphosphates (dNTPs) as substrates.
• The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously, resulting in Okazaki fragments.

Transcription

• Transcription is the process of copying genetic information from DNA to RNA.
• RNA polymerase synthesizes RNA in the 5' to 3' direction.
• Transcription units (genes) contain promoters for RNA polymerase binding and terminators that signal termination.
• Eukaryotic transcripts (hnRNA) need processing including splicing (removal of introns) to form active mRNA.

Translation

• Translation is the process of converting mRNA into proteins.
• Ribosomes provide the enzyme(ribozyme) environment for amino acid translation and binding.
• mRNA codons (3-base sequences) determine amino acid sequence.
• The process comprises three stages: initiation, elongation, and termination.

Regulation of Gene Expression

• Regulation controls the timing and extent of gene expression.
• Induction and repression are mechanisms of gene regulation.
• Operons are clusters of genes that are coordinately regulated, including the Lac Operon.

Test your knowledge on the principles and practices of organic farming. From pest management methods to the benefits of organic methods, this quiz will challenge your understanding of sustainable agriculture. Learn how organic farming differs from conventional practices.