Tiêu đề 22. GENE STRUCTURE.pdf ✅

PHARMD GURU Page 1 1) INTRODUCTION TO GENES AND GENOMIC ORGANIZATION: Genes are the fundamental units of heredity, carrying the instructions required for protein and RNA synthesis. Genomic organization refers to the arrangement of genes and non-coding regions within the complete set of an organism’s DNA, known as the genome. KEY FEATURES OF GENOME ORGANIZATION:  Prokaryotic Genome: Genes are arranged in continuous stretches without introns and are often grouped into operons for coordinated expression.  Eukaryotic Genome: Genes are interrupted by introns and contain regulatory sequences like enhancers and silencers, allowing complex gene regulation. Understanding genome structure helps in studying gene expression, replication, and cellular functions. 2)GENE STRUCTURE: A. ORGANIZATION OF GENES: A gene is a segment of DNA that encodes a specific protein or functional RNA. It consists of both coding (exons) and non-coding (introns and regulatory regions). Figure 1: Hierarchical Organization of Chromatin Structure THE GENE: GENOME STRUCTURE AND FUNCTION

PHARMD GURU Page 3 D. CONCEPT OF OPERONS IN PROKARYOTES:  Definition: An operon is a cluster of genes controlled by a single promoter and operator sequence.  Example: Lac Operon (E. coli)  Regulates lactose metabolism.  The lac repressor binds to the operator and prevents transcription in the absence of lactose.  When lactose is present, it binds to the repressor, allowing gene expression.  Significance: Ensures efficient gene regulation based on environmental needs. Figure 3: Diagram illustrating prokaryotic and eukaryotic gene structures Figure 4: Flow of genetic information from DNA to RNA to protein, illustrating
PHARMD GURU Page 4 3)ELUCIDATION OF THE GENETIC CODE: The genetic code is a set of rules by which the information encoded in DNA or RNA sequences is translated into proteins by living cells. It defines how sequences of nucleotides correspond to specific amino acids, the building blocks of proteins. Understanding the elucidation of the genetic code was a monumental achievement in molecular biology, revealing how genetic information is read and translated into functional proteins. A. DISCOVERY AND DECODING OF THE GENETIC CODE: a) HISTORICAL BACKGROUND: The journey to decode the genetic code began in the 1950s, following the discovery of the DNA double helix by James Watson and Francis Crick. Scientists knew that DNA carried genetic information, but how this information directed protein synthesis remained a mystery. b) KEY EXPERIMENTS: Marshall Nirenberg and Heinrich Matthaei made significant contributions to deciphering the genetic code in 1961. They conducted experiments using synthetic RNA sequences in cell-free systems to identify which amino acids were produced. Figure 5: Diagram illustrating the elucidation of the genetic code and its reading  Poly-U Experiment: By adding poly-uracil (poly-U) RNA to a cell-free extract containing ribosomes and amino acids, they observed the synthesis of a polypeptide composed entirely of phenylalanine. This showed that the codon UUU codes for phenylalanine.