Genetics and Genetic Engineering Lecture Notes PDF

lecture 1 (30-9-2024) Genetics and genetic engineering  CONTENTS OF THIS lecture Introduction Divisions of 01 Of Genetics and 02 genetic engineering Genetics 03 CELL CYCLE 04 Phases of Cell Cycle Regulation of 05...

lecture 1 (30-9-2024) Genetics and genetic engineering  CONTENTS OF THIS lecture Introduction Divisions of 01 Of Genetics and 02 genetic engineering Genetics 03 CELL CYCLE 04 Phases of Cell Cycle Regulation of 05 06 M phase the cell cycle:  INTRODUCTION Genetics 1-is the study of inheritance. 2-It is a broad science that examines the molecular basis of inheritance at the cellular level, the transmission of traits from generation to generation, and the movement of genes within and between populations. Divisions of Genetics Traditionally, the study of genetics has been divided into three major sub disciplines: (transmission genetics, molecular genetics, and population genetics). 1-Transmission genetics 2-Molecular genetics 3- Population genetics  The Importance of Genetics 1-in agriculture 2-The pharmaceutical industry 3-The biotechnology industry 4-In medicine The Future of Genetics CELL CYCLE AND CELL DIVISION!  CELL CYCLE AND CELL DIVISION! Are you aware that all organisms, even the largest start their life from a single cell? CELL CYCLE 1-The cell cycle is the life story of a cell 2-The stages through which it passes from one division to the next. 3-This process is critical to genetics because, through the cell cycle, the genetic instructions for all characteristics are passed from parent lo daughter cells. 4- A new cell metabolizes, grows, and develops. 5- At the end of its cycle, the cell divides to produce two cells, which can then undergo additional cell cycles. Cell division 1-is a very important process in all living organisms. 2- During the division of a cell, DNA replication and cell growth also take place. 3- All these processes, i.e., cell division, DNA replication, and cell growth, hence, must take place in a coordinated way to ensure correct division and formation of progeny cells containing intact genomes. 1- Phases of Cell Cycle The cell cycle is divided into two basic phases: 1-Interphase 2- M Phase (Mitosis phase) The M Phase represents the phase when the actual cell division or mitosis occurs. The interphase represents the phase between two successive M phases. It is significant to note that in the 24-hour average duration of cell cycle of a human cell, cell division proper lasts for only about an hour. The interphase lasts more than 95% of the duration of cell cycle. The M Phase starts with the nuclear division, corresponding to the separation of daughter chromosomes (karyokinesis) and usually ends with division of cytoplasm The interphase is the period between cell division ,though called the( resting phase), is the time during which the cell is preparing for division by undergoing both cell growth and DNA replication in an orderly manner. The interphase is divided into three further phases: G1 phase (Gap 1) S phase (Synthesis) G2 phase (Gap 2) How do animals continue to grow all their lives? Do all cells divide all the time? Do you think all cells continue to divide in all animals? Can you tell the name and the location of tissues having cells that divide all their life? 1-G1 phase (Gap 1) 1-It is the longest and typically lasts (about 9 hours). 2-G1 phase corresponds to the interval between mitosis and initiation of DNA replication. 3-During G1 phase the cell is metabolically active and continuously grows and proteins necessary for cell division are synthesized but does not replicate its DNA. 4- The RNA and protein synthesis occurs, The cell attains its full size. 5-The cell performs its function. 6-Duplication of centrosomes occurs near the transition between G1and S phase. Quiescent stage (G0) 1-Before reaching the G1/S checkpoint, cells may pass into a non dividing phase called G0 G0 1-(It is arrested phase is referred to as gap zero G0), which is a stable state during which cells usually maintain a constant size. 2-Some cells in the adult animals do not appear to exhibit division (e.g., heart cells) and many other cells divide only occasionally, as needed to replace cells that have been lost because of injury or cell death 3- These cells that do not divide further exit G1 phase to enter an inactive stage called quiescent stage (G0) of the cell cycle. 4- Cells in this stage remain metabolically active but no longer proliferate unless called on to do so depending on the requirement of the organism. 5-They can remain in G0 for an extended period of time, even indefinitely, or they can reenter G1 and complete the cell cycle. GO may be permanent or temporary. 2-S phase (Synthesis of DNA) 1- S or synthesis phase marks the period during which DNA synthesis or replication takes place. 2- During this time the amount of DNA per cell doubles. 3- If the initial amount of DNA is denoted as 2C then it increases to 4C. 4-However, there is no increase in the chromosome number; if the cell had diploid or 2n number of chromosomes at G1, even after S phase the number of chromosomes remains the same, i.e., 2n. 5- In animal cells, during the S phase, DNA replication begins in the nucleus, and the centriole duplicates in the cytoplasm. 6-DNA synthesis lasts about 5hours in mammalian cells 7-DNA synthesis must take place before the cell can proceed to mitosis. 8- Some DNA replicates early in the S phase and some replicates later. ( Early replicating DNA contains a higher portion of active genes than late replicating DNA). 1-Before S phase, each chromosome is composed of one chromatid; 2-following S phase, each chromosome is composed of two chromatids. 3-The DNA replicates itself and the chromosomes then consist of two identical sister chromatids. Types of chromosomes: 1- S-Chromosomes made of one DNA molecule (interphase chromosomes = chromatin or chromatids). 2- d-Chromosomes (mitotic chromosomes):are formed during the S phase. Each d-chromosome is formed of two chromatids, linked at the centromere. Each chromatid is made of a DNA molecule. 3- G2 (gap 2) 1-During the G2 phase, proteins are synthesized in preparation for mitosis 2-several biochemical events necessary for cell division take place while cell growth continues. 3-Duplication of the centrosome is completed. 4- It needs about 3 hours. Regulation of the cell cycle: 1- The cell cycle is regulated by growth factors that control cell proliferation to keep its coordination with the needs of the living organism. 2-Several checkpoints control the transition between the cycle stages. Checkpoints 1- Biochemical circuits that regulate cell-cycle transitions in response to the physiological condition of the cell and signals from its environment. Checkpoints of the cell cycle: 1. The restriction checkpoint (G1 / S checkpoint): It occurs in the G1 phase. It detects the cell size & its interactions with the surrounding environment. Cells that do not receive appropriate growth stimuli do not progress past this point (G1 phase) and will be die by apoptosis. It is the most important checkpoint in the cell cycle. 2. DNA damage checkpoints: It occurs in G1, S, and G2 phases. It blocks cell cycle progression until repair of the damaged DNA or cell apoptosis occurs. 3. The unreplicated DNA checkpoint(G2/M checkpoint): It occurs in the G2 phase. It prevents progression of the cycle into the mitosis before complete synthesis of DNA. The important is reached in G2; after this checkpoint has been passed, the cell is ready to divide and enters M phase. 4. The spindle-assembly checkpoint (the metaphase checkpoint): It occurs in mitosis. It prevents entry into anaphase until all chromosomes have attached properly to the mitotic spindle. 5. The chromosome-segregation checkpoint: It occurs in telophase. It prevents the cytokinesis until all of the chromosomes have been correctly separated. Note 1-Interphase length varies from cell-type to cell type; a typical dividing mammalian cell spends about 9hours in G1, 5hours in S, and 3 hours in G2. 2-Interphase, the chromosomes are in a relatively relaxed and are visible ,only as diffuse chromatin, uncoiled state, and individual chromosomes cannot be seen with the use of a microscope.  M phase This stage lasts only 1 – 2 hours in most mammalian cells. Division (Mitosis) is the process by which cells reproduce themselves, creating two daughter cells that are genetically identical to one another and to the original parent cell. Mitosis is itself divided into stages yield into, six stages: the five stages mitosis (prophase, prometaphase, metaphase, anaphase, and telophase) and cytokinesis. M phase is a continuous process, and its separation into these stages is somewhat artificial. What are the genetically Important results of the cell cycle? Control of the cell cycle THANKS! DO YOU HAVE ANY QUESTIONS? CREDITS: This presentation template was created by Slidesgo, and includes icons by Flaticon, and infographics & images by Freepik