General Biology 1 Past Paper 2024-2025 PDF

GENERAL BIOLOGY 1 | SY 2024 - 2025 UNIT 2 - GENETICS Lesson 1: Central Dogma of Molecular Biology Let me ask you a question… What if you could edit your own genes to eliminate diseases or even enhance your abilities? 01 Central Dogma of Molecular...

GENERAL BIOLOGY 1 | SY 2024 - 2025 UNIT 2 - GENETICS Lesson 1: Central Dogma of Molecular Biology Let me ask you a question… What if you could edit your own genes to eliminate diseases or even enhance your abilities? 01 Central Dogma of Molecular Biology Replication Learning Objectives Discuss the relationship between genes, proteins, and RNAs Explain the process of DNA Replication Introduction During the expression of the protein coding gene, the information passes from the DNA and from it is transferred to the RNA and finally to proteins. - Francis Crick Introduction double-helix structure of DNA Central Dogma Central Dogma The Central Dogma of biology is that the information stored in DNA is transferred to RNA molecules during TRANSCRIPTION and to proteins during TRANSLATION. Central Dogma Segments of DNA (GENES) are the instructions that control the production of proteins. Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA. RNA contains coded information for making proteins Case Study Cystic Fibrosis is a genetic disorder that affects the respiratory and digestive systems. It is caused by mutations in the CFTR gene (Cystic Fibrosis Transmembrane Conductance Regulator), which encodes a protein responsible for regulating the flow of salt and water in and out of cells. Case Study Mutation of CFTR gene is located on chromosome 7, called ΔF508 Case Study Clinical Manifestations? Before we deep dive into Central Dogma… Before we deep dive into Central Dogma… Central Dogma REPLICATION Replication a. Semi-conservative b. Starts at the “origin” c. Synthesis always begins in the 5’-3’ direction d. Can be uni or bidirectional e. Semi-discontinuous f. RNA primers required Semi-conservative each of the two newly formed DNA molecules consists of one original (parental) strand and one newly synthesized strand this method of replication ensures that each daughter cell receives an exact copy of the DNA Starts at the origin begins at specific locations on the DNA molecule known as origins of replication these are particular sequences of DNA where the replication process is initiated Synthesis always begins in the 5’-3’ direction Each strand of DNA has a directionality based on the orientation of its sugar-phosphate backbone. The backbone is made up of repeating units of deoxyribose sugars linked by phosphate groups Can be uni or bidirectional Replication forks move in one or opposite directions Semi-discontinuous one strand (the leading strand) is synthesized continuously, while the other strand (the lagging strand) is synthesized discontinuously in fragments RNA primers required provide the starting point for DNA synthesis Core proteins at the replication fork 1. Topoisomerase - prevents torsion by DNA breaks 2. Helicase - separates 2 strands 3. Primase - RNA primer synthesis 4. Single strand binding proteins - prevent reannealing of single strands 5. DNA polymerase - synthesis of new strand 6. Tethering protein - stabilises polymerase 7. DNA ligase - seals nicks (small gaps) via phosphodiester linkage Mechanism of DNA Replication 1. Initiation - Origin of replication - Unwinding - Priming 2. Elongation - Leading strand - Lagging Strand - Fragment Joining 3. Termination - Completion Central Dogma  How does the understanding of DNA replication and the ΔF508 mutation in cystic fibrosis inform the potential for CRISPR-Cas9 technology to correct genetic disorders? Reflection Learning Objectives Discuss the relationship between genes, proteins, and RNAs Explain the process of DNA Replication 01 Central Dogma of Molecular Biology Replication 01 Central Dogma of Molecular Biology Transcription and Translation Learning Objectives Explain the process of DNA Transcription and Translation. Compare and contrast the transcription and translation processes in prokaryotic and eukaryotic cells. Central Dogma Gene Expression Gene Expression The conversion of genes into their functional products. Gene Expression The conversion of genes into their functional products. Transcription: DNA is transcribed into RNA Translation: RNA is translated into a protein 01 Central Dogma of Molecular Biology Transcription and Translation Terms Codons A sequence of three consecutive nucleotides in a DNA or RNA molecule that codes for a specific amino acid. Transcription Transcription group of DNA that initiates transcription 1. Initiation - Promoter Region - RNA Polymerase binding - Formation of Transcription bubble ezyme that synthesizes RNA Transcription 2. Elongation - RNA Synthesis - Proofreading Transcription 3. Termination - Termination Signal - Release of RNA Transcript Key Enzymes 1. RNA Polymerase - enzyme responsible for synthesizing RNA 2. Transcription Factors - Proteins that assist in the initiation of transcription by helping RNA polymerase bind to the promoter Case study Thalassemia is a heterogeneous group of blood disorders affecting the hemoglobin genes and resulting in ineffective erythropoiesis. In Beta Thalassemia, mutations occur in the HBB gene on chromosome 11, which codes for the beta-globin protein. These mutations often affect the promoter region or the splicing sites of the gene. Case study 1. How do mutations in the promoter region affect gene expression? Translation Translation 1. Initiation - Ribosome Assembly - tRNA Binding - Large Ribosomal Subunit Binding Translation 2. Elongation - Codon Recognition - Peptide Bond Formation - Translocation Translation 3. Termination - Stop Codon Recognition - Release of Polypeptide Key Players 1. mRNA 2. tRNA 3. Ribosomes Case study A 25-year-old female presents with a persistent respiratory infection that has not responded to over-the-counter treatments. She reports a cough, fever, and shortness of breath lasting for over a week. After a physical examination and a sputum culture, the patient is diagnosed with a bacterial infection caused by Streptococcus pneumoniae. The physician prescribes tetracycline, an antibiotic known for its effectiveness against a broad spectrum of bacteria, including Streptococcus pneumoniae. Case study Tetracycline works by binding to the 30S ribosomal subunit in bacteria, blocking the attachment of tRNA to the mRNA-ribosome complex. This prevents the bacteria from synthesizing proteins necessary for growth and survival, ultimately leading to their death. What are the implications of using antibiotics that affect translation?  Transcription in Prokaryotes vs Eukaryotes 1. Compartmentalization a. In eukaryotes, transcription and translation are separated by the nuclear membrane; in prokaryotes, they can occur simultaneously. 2. mRNA processing a. Eukaryotic mRNA undergoes significant post-transcriptional modifications, whereas prokaryotic mRNA does not. Prokaryotic Transcription: Location: Occurs in the cytoplasm, as prokaryotes lack a nucleus. mRNA Characteristics: Prokaryotic mRNA is often polycistronic, meaning a single mRNA can encode multiple proteins. It is ready for translation immediately after transcription without any processing. No Introns: Prokaryotic genes lack introns; therefore, mRNA does not undergo splicing. Eukaryotic Transcription: Location: Takes place in the nucleus, allowing for separation from translation. mRNA Characteristics: Eukaryotic mRNA is typically monocistronic, encoding only one protein. It undergoes extensive processing before being exported to the cytoplasm. RNA Processing: Includes splicing to remove introns, addition of a 5’ cap, and a 3’ poly-A tail, all of which are crucial for mRNA stability and translation efficiency.  Translation in Prokaryotes vs Eukaryotes 1. Ribosome structure a. The size and structure of ribosomes differ between prokaryotes and eukaryotes, affecting translation dynamics. 2. Initiation process a. Eukaryotic translation initiation is more complex, involving multiple initiation factors and the 5’ cap structure. Prokaryotic Translation: Simultaneous with Transcription: Since prokaryotes lack a nucleus, translation can begin on an mRNA molecule even before transcription is complete. Ribosomes: Prokaryotic ribosomes are 70S, composed of a 50S large subunit and a 30S small subunit. Initiation: The Shine-Dalgarno sequence on the mRNA aligns with the 16S rRNA in the small ribosomal subunit to position the start codon correctly. Eukaryotic Translation: Separate from Transcription: Translation occurs in the cytoplasm, following the export of fully processed mRNA from the nucleus. Ribosomes: Eukaryotic ribosomes are 80S, composed of a 60S large subunit and a 40S small subunit. Initiation: The small ribosomal subunit binds to the 5’ cap of the mRNA and scans for the start codon (AUG). Initiation factors play a crucial role in assembling the translation initiation complex. Translation Central Dogma Learning Objectives Explain the process of DNA Transcription and Translation. Compare and contrast the transcription and translation processes in prokaryotic and eukaryotic cells. 01 Central Dogma of Molecular Biology Transcription and Translation