Describe DNA transcription and translation, and explain the steps of DNA replication.

Fresh day C.PRIDE, let's solve. a) (i) Transcription: This is the process in molecular biology where a segment of DNA is copied into RNA by the enzyme RNA polymerase*. The resulting RNA molecule, often messenger RNA (mRNA), carries the genetic information from the DNA to the ribosomes for protein synthesis. (ii) Translation: This is the process where the genetic code carried by messenger RNA (mRNA) is decoded to produce a specific sequence of amino acids, forming a polypeptide chain* (protein). This occurs at the ribosomes, with the help of transfer RNA (tRNA) molecules. b) The process by which a DNA molecule makes an exact copy of itself is called DNA replication. It is a semi-conservative process, meaning each new DNA molecule consists of one original strand and one newly synthesized strand. Step 1: Unwinding and Separation. The enzyme DNA helicase unwinds the double helix, breaking the hydrogen bonds between complementary base pairs and separating the two DNA strands. This creates a replication fork. Step 2: Primer Binding. Short RNA sequences called primers are synthesized by primase and bind to specific points on the separated DNA strands. These primers provide a starting point for DNA synthesis. Step 3: Elongation. The enzyme DNA polymerase then adds complementary deoxyribonucleotides to each original strand, following the base-pairing rules (Adenine with Thymine, Guanine with Cytosine). One new strand, the leading strand, is synthesized continuously in the 5' to 3' direction. The other new strand, the lagging strand, is synthesized discontinuously in short segments called Okazaki fragments. Step 4: Ligation. The RNA primers are removed and replaced with DNA nucleotides by another DNA polymerase. The Okazaki fragments on the lagging strand are then joined together by the enzyme DNA ligase, forming a continuous strand. Step 5: Proofreading. DNA polymerase also has a proofreading function to correct any errors in nucleotide incorporation, ensuring high fidelity of replication. The result is two identical DNA molecules, each containing one original strand and one newly synthesized strand. c) Here are four differences between DNA and RNA: • Sugar: DNA contains deoxyribose sugar, while RNA contains ribose sugar. • Nitrogenous Bases: DNA contains the base thymine (T), whereas RNA contains uracil (U) in its place (both have Adenine, Guanine, and Cytosine). • Structure: DNA is typically a double-stranded helix, while RNA is typically single-stranded. • Function: DNA primarily functions in the long-term storage and transmission of genetic information, while RNA is involved in gene expression, carrying genetic information from DNA to ribosomes and participating in protein synthesis. d) Carbohydrates play crucial structural roles in both plants and animals: • In Plants: The primary structural carbohydrate is cellulose. It forms the rigid cell walls of plant cells, providing structural support, strength, and protection against osmotic lysis. Other carbohydrates like hemicellulose and pectin also contribute to the structure and integrity of the cell wall. • In Animals: Chitin is a major structural carbohydrate found in the exoskeletons of insects and crustaceans, and in the cell walls of fungi, providing protection and support. Glycosaminoglycans (GAGs), such as chondroitin sulfate and hyaluronic acid, are important components of the extracellular matrix in connective tissues, providing lubrication, shock absorption, and structural integrity. Carbohydrates also form glycoproteins and glycolipids on cell surfaces, which are crucial for cell recognition and adhesion. What's next?