Tiêu đề 22. GENE STRUCTURE.pdf ✅

PHARMD GURU Page 2 B. BASIC COMPONENTS OF A GENE: COMPONENT FUNCTION Exons Coding regions that form the final mRNA and encode proteins. Introns Non-coding regions removed during RNA processing. Promoter A DNA sequence where RNA polymerase binds to initiate transcription. Enhancer A distant regulatory element that increases gene transcription. Silencer A DNA sequence that represses gene transcription. Figure 2: Gene Structure C. DIFFERENCES IN GENE ORGANIZATION: FEATURE PROKARYOTES EUKARYOTES Gene Structure Continuous genes without introns. Genes contain introns and exons. Regulation Genes arranged in operons for coordinated regulation. Genes are independently regulated with enhancers and silencers. Genome Size Small and compact. Larger with repetitive DNA and regulatory sequences.
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.