Lecture 1: Inheritance of Mutations and Microorganisms PDF

Inheritance of Mutations and Microorganisms Dr. Manal Mohamed Zaater Lecturer of Genetics Fac. of Agri., Damietta University  Structure and Function of the Genetic Material Genetics: the study of genes, how they carry information, how information is e...

Inheritance of Mutations and Microorganisms Dr. Manal Mohamed Zaater Lecturer of Genetics Fac. of Agri., Damietta University  Structure and Function of the Genetic Material Genetics: the study of genes, how they carry information, how information is expressed, and how genes are replicated Chromosomes: structures containing DNA that physically carry hereditary information; the chromosomes contain genes Genes: segments of DNA that encode functional products, usually proteins Genome: all the genetic information in a cell Genetic code, the sequence of nucleotides in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) that determines the amino acid sequence of proteins. https://www.britannica.com/science/genetic-code Central Dogma Genotype: the genetic makeup of an organism Phenotype: expression of the genes What are Microorganisms? Microorganisms are microscopic organisms that are classified into different groups such as bacteria, fungi, archaea, and protists. Prokaryotic Cell The term “prokaryote” is derived from the Greek word “pro“, (meaning: before) and “karyon” (meaning: kernel). It translates to “before nuclei.“ Structurally, prokaryotes have a capsule enveloping their entire body, and it functions as a protective coat. This is crucial for preventing the process of phagocytosis (where the bacteria gets engulfed by other eukaryotic cells, such as macrophages) The pilus is a hair-like appendage found on the external surface of most prokaryotes and it helps the organism to attach itself to various environments. It is also called attachment pili. It is commonly observed in bacteria. https://byjus.com/biology/prokaryotic-and-eukaryotic-cells/ Right below the protective coating lies the cell wall, which provides strength and rigidity to the cell. Further down lies the cytoplasm that helps in cellular growth, and this is contained within the plasma membrane, which separates the interior contents of the cell from the outside environment. Within the cytoplasm, ribosomes exist, and it plays an important role in protein synthesis. It is also one of the smallest components within the cell.  Eukaryotic Cell The term “Eukaryotes” is derived from the Greek word “eu“, (meaning: good) and “karyon” (meaning: kernel), therefore, translating to “good or true nuclei.” Eukaryotes are more complex and much larger than prokaryotes. They include almost all the major kingdoms except kingdom Monera  Eukaryotic Cell Structurally, eukaryotes have a cell wall, which supports and protects the plasma membrane. The cell is surrounded by the plasma membrane, and it controls the entry and exit of certain substances. The nucleus contains DNA, which is responsible for storing all genetic information. The nucleus is surrounded by the nuclear membrane. Within the nucleus exists the nucleolus, and it plays a crucial role in synthesizing proteins. Eukaryotic cells also contain mitochondria, which are responsible for the creation of energy, which is then utilized by the cell. Present in only plant cells, chloroplasts are the subcellular sites of photosynthesis. The endoplasmic reticulum helps in the transportation of materials. Besides these, there are also other cell organelles that perform various other functions, and these include ribosomes, lysosomes, Golgi bodies, cytoplasm, chromosomes, vacuoles and centrosomes.  1865 Mende; documents patterns of heredity in pea plants In his garden peas, Mendel observed—when considering the inheritance patterns of a single trait (e.g., seed color)—that the ratio of progeny from hybrid plants, with respect to that trait, was 3:1, namely three offspring with the dominant trait to everyone with the recessive trait https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9335310/  The First Piece of the Puzzle: Miescher Discovers DNA Although few people realize it, 1869 was a landmark year in genetic research, because it was the year in which Swiss physiological chemist Friedrich Miescher first identified what he called "nuclein" inside the nuclei of human white blood cells. https://www.nature.com/scitable/topicpage/discovery-of-dna-structure-and-function-watson-397/  1902 Sutton and Boveri propose chromosome theory of heredity The Boveri –Sutton chromosome theory (also known as the chromosome theory of inheritance) is a fundamental unifying theory of Genetics which identifies chromosomes as the carriers of genetic material Walter Sutton (left) and Theodor Boveri (right) https://en.wikipedia.org/wiki/Boveri%E2%80%93Sutton_chromosome_theory  Thomas Hunt Morgan's experiments. The fruit fly (Drosophila melanogaster) as a model system. Boveri and Sutton's chromosome theory of inheritance states that genes are found at specific locations on chromosomes, and that the behavior of chromosomes during meiosis can explain Mendel’s laws of inheritance. Thomas Hunt Morgan, who studied fruit flies, provided the first strong confirmation of the chromosome theory. Morgan discovered a mutation that affected fly eye color. He observed that the mutation was inherited differently by male and female flies. Based on the inheritance pattern, Morgan concluded that the eye color gene must be located on the X chromosome. https://www.khanacademy.org/science/ap-biology/heredity/chromosomal-inheritance-ap/a/discovery-of-the-chromosomal-basis-of-inheritance  Hermann Joseph Muller's Study of X-rays as a Mutagen, (1926-1927) Hermann Joseph Muller conducted three experiments in 1926 and 1927 that demonstrated that exposure to x-rays, a form of high-energy radiation, can cause genetic mutations, changes to an organism's genome, particularly in egg and sperm cells https://embryo.asu.edu/pages/hermann-joseph-mullers-study-x-rays-mutagen-1926-1927  1928 Griffith experiment Griffith's experiment, performed by Frederick Griffith and reported in 1928, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation. https://en.wikipedia.org/wiki/Griffith%27s_experiment  1930 Hämmerling Experiments In a clever set of experiments in the 1930s and 1940s, German scientist Joachim Hämmerling (1901–1980), using the single-celled alga Acetabularia as a microbial model, established that the genetic information in a eukaryotic cell is housed within the nucleus. Acetabularia spp. are unusually large algal cells that grow asymmetrically, forming a “foot” containing the nucleus, which is used for substrate attachment; a stalk; and an umbrella-like cap—structures that can all be easily seen with the naked eye. In an early set of experiments, Hämmerling removed either the cap or the foot of the cells and observed whether new caps or feet were regenerated. He found that when the foot of these cells was removed, new feet did not grow; however, when caps were removed from the cells, new caps were regenerated. This suggested that the hereditary information was located in the nucleus-containing foot of each cell. https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_(OpenStax)/10%3A_Biochemistry_of_the_Geno me/10.01%3A_Using_Microbiology_to_Discover_the_Secrets_of_Life  Barbara McClintock 1931 demonstrated genetic recombination in corn Some of the most profound genetic discoveries have been made with the help of various model organisms that are favored by scientists for their widespread availability and ease of maintenance and proliferation. One such model is Zea mays (maize), particularly those plants that produce variably colored kernels. Because each kernel is an embryo produced from an individual fertilization, hundreds of offspring can be scored on a single ear, making maize an ideal organism for genetic analysis. Indeed, maize proved to be the perfect organism for the study of transposable elements (TEs), also known as "jumping genes," which were discovered during the middle part of the twentieth century by American scientist Barbara McClintock. McClintock's work was revolutionary in that it suggested that an organism's genome is not a stationary entity, but rather is subject to alteration and rearrangement-a concept that was met with criticism from the scientific community at the time. However, the role of transposons eventually became widely appreciated, and McClintock was awarded the Nobel Prize in 1983 in recognition of this and her many other contributions to the field of genetics. https://www.nature.com/scitable/topicpage/barbara-mcclintock-and-the-discovery-of-jumping-34083/  1941 Beadle and Tatum describe the one gene one enzyme hypothesis In 1941, over 30 years after Garrod’s discovery, Beadle and Tatum built on this connection between genes and metabolic pathways. Their research led to the “one gene, one enzyme” hypothesis, which states that each enzyme that acts in a biochemical pathway is encoded by a different gene. https://courses.lumenlearning.com/suny-mcc-microbiology/chapter/using-microbiology-to-discover-the-secrets-of-life/ 1944 Avery MacLeod and McCarty show that DNA transforming principle responsible for heredity In 1944, three Canadian and American researchers, Oswald Avery, Colin MacLeod, and Maclyn McCarty, set out to identify Griffith's "transforming principle." https://www.khanacademy.org/science/biology/dna-as-the-genetic-material/dna-discovery-and-structure/v/establishing-dna-as-transformation-principle  Erwin Chargaff discovery 1950 Chargaff's rules (given by Erwin Chargaff) state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine. Further, a 1:1 stoichiometric ratio of purine and pyrimidine bases (i.e., A+G=T+C) should exist. This pattern is found in both strands of the DNA. They were discovered by Austrian-born chemist Erwin Chargaff[ in the late 1940s. 1952 Hershey and Chase use radioactive labeling to prove that DNA is responsible for Heredity 1953 Watson and Crick Discovered the Structure of DNA 1990 Genome sequencing begin  1961 Jacob and Monod proposed the existence of mRNA In 1961 Jacob and Monod proposed the existence of a messenger ribonucleic acid (mRNA), a substance whose base sequence is complementary to that of deoxyribonucleic acid (DNA) in the cell. They postulated that the messenger carries the “information” encoded in the base sequence to ribosomes, the sites of protein synthesis; here the base sequence of the messenger RNA is translated into the amino acid sequence of a proteinaceous enzyme.  2024 Nobel Prize for miRNA Victor Ambros and Gary Ruvkun won this year’s Physiology or Medicine award for the discovery of microRNA and its role in post-transcriptional gene regulation.