Molecular Genetics

• A telocentric chromosome is a chromosome in which the centromere is located at the terminal end of the chromosome and their shape is similar to the letter i.
  
• These chromosomes have a repetitive nucleotide sequence at each end of chromosomes. 
• It seals and protects each end of the chromosomes from deterioration or fusion with the neighbouring chromosomes during cell division.
• So, the correct answer is 'Seal ends of chromosomes'.

The nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.

During post-transcriptional processing in eukaryotes, primary transcripts undergo splicing to remove non-coding introns and join coding exons together. Therefore, the mature mRNA contains exons but lacks introns.

Informosomes are messenger RNA molecules combined with protein, forming ribonucleoprotein complexes that remain stable and untranslated in the cytoplasm for extended periods. They were first discovered by Spirin in embryonic development.

Cycloheximide inhibits protein synthesis in eukaryotes by blocking the elongation phase during translation, making option A correct. Option D has a typo (erythromycin, not 'erythyromycin'). Formylated mRNA is for prokaryotic initiation, and single mRNA producing multiple products (polycistronic) is prokaryotic.

Gene silencing by dsRNA makes use of the naturally occurring cell machinery that is involved in the processing of miRNA in eukaryotic cells. It does not provide any defense mechanism. So the correct answer is ' RNAi silencing takes place in all eukaryotic cells for cellular defense'.

• Transgenic plants are those plants whose genome is altered by the addition of one or more transgenes. Tobacco plant is the most common plant for expressing the transgenes. As the genome of tobacco plant is completely studied. The transgenic plants are transcribed in such a way that they develop tolerance against stress, salt, herbicide and also for vaccine productions. There are several transgenes which are inserted in tobacco plant like cry2Aa gene which gives resistance against any worms.
  
• The Meloidogyne does not perform the conversion of sites like pre-RISC to RISC. The Meloidogyne gene is obtained by the species Meloidegyne incognita which are mainly responsible for causing root knot in plants.
• Therefore the correct answer is option "A".

AUG is the primary initiation codon in both prokaryotes and eukaryotes. GUG can also serve as an initiation codon in some prokaryotic systems.

Coenzymes are organic cofactors which are required for enzymatic action of certain enzymes. NADP is a coenzyme form of vitamin nicotinamide or niacin.

DNA polymerase is an enzyme used in DNA replication. It synthesizes DNA on a DNA template. Bacteria have three different DNA polymerases, i.e., DNA pol I, DNA pol II and DNA pol III; while eukaryotes have several DNA polymerase enzymes.

RNA polymerase participates in RNA synthesis during transcription process. It synthesizes RNA on DNA template.

Ribozymes are also known as ribonucleic acid enzymes. These are RNA molecules which helps in the catalysis of a particular reaction. It was discovered in the year 1982. The RNA can act as both genetic material and can act as a biocatalyst. It acts as a part of ribosome which attaches to the amino acid during protein synthesis. It increases the rate and specificity of peptide bond synthesis and phosphodiester bond. So, the correct answer is option A.

Enzymes are biological catalysts which speed up the biological reactions. All metabolic reactions in a cell are catalyzed by enzymes. Almost all enzymes are proteins. There are some nucleic acids that behave like enzymes. These are called ribozymes. Ribozymes are molecules of ribonucleic acid with catalytic activity.