Genetics - 01 Intro to Genetics

HUMAN GENETICS WITH CYTOGENETICS INTRODUCTION TO GENETICS LESSON 1 - INTRODUCTION: GENETICS, ITS ORIGIN AND DEFINITION INTRODUCTION • • • • Genetics is one of the major fields in Biology. It is about genes, the so-called "blueprint" of life. The genes determine the traits (variations) that each person has and each person has a unique set of genes. Genetics studies how traits are passed from parents to their offspring, that is from one generation to the next. The passing of traits from parents to offspring is known as heredity, hence, genetics is also the study of heredity. This introduction to genetics takes you through the basic components of genetics such as DNA, genes, chromosomes and genetic inheritance. This lesson also includes a discussion on the origin of Genetics. Genetics is built around molecules called DNA. Genes are segments of DNA, therefore, DNA molecules hold all the genetic information for an organism. It provides cells with the information they need to perform tasks that allow an organism to grow, survive and reproduce. A gene tells a cell to perform one specific task. Heredity is what makes children look like their parents. During reproduction, DNA is replicated and passed from a parent to their offspring. This inheritance of genetic material by offspring influences the appearance and behavior of the offspring. The environment that an organism lives in can also influence how genes are expressed. VARIATIONS • • • • • • • TYPES OF VARIATIONS • • • LESSON 2 - TYPES AND CAUSES OF VARIATION INTRODUCTION • • • The set of genes or the genotype of the person determines her or his phenotype, the observable traits. The traits or the characteristics of an individual, a plant or animal can be unique only to the individual (individual characteristics) or can be observed in most members of their species (Species characteristics). The species characteristics are observed as similarities, while the individual characteristics are the differences. • WHAT IS GENETICS? • • • • • • From Greek words: o “Genetikos” = genitive/generative o “Genesis” = origin” o “Genea” = “genes”; race or generation o Gen= to produce, to become, or to grow into something SW: Can you think of words that have “gen” either as prefix or suffix. Try to give its meaning. It is the study of genes and how they are transmitted from parents to offspring (Heredity) Explains one’s origin or ancestry “How one becomes what he is like?” Variations: Individuals of the same species may have characteristics common to all of them (Species characteristics=denote common origin), and yet they may differ from one another (Individual characteristics) The basic quality of living organisms Similarities (Species Characteristics) Differences (Individual Characteristics) Provides the raw materials for adaptation Phenotype – various observable features by which we recognize the organism Genotype – type of genes or hereditary material in the organism Phenocopies – environmental alterations of phenotype o Ex. Straightening of curly hair • Morphological or Structural o Physical traits or gross anatomical features ▪ Ex: • shape of the face, ears, eyes • color of the eyes, hair, o Cellular, Subcellular and Molecular traits ▪ Ex: • Kind of hemoglobin in the RBC • Kind of glycoproteins on the cell membrane • Kind of DNA Physiological or Functional o Biochemical and biophysical processes o Ex: ▪ inability to absorb glucose ▪ inability to distinguish colors ▪ failure to perform photosynthesis ▪ inability to synthesize certain amino acid Behavioral o The combined structural and physiological traits o Pattern of reactions to its environment o Ex. ▪ IQ ▪ Mental retardation ▪ Tolerance level Sexual o The most important phenotypic characteristics of an organism o Capacity for reproduction together with the features associated with it o Primary Sexual Traits – differences in external genitalia and gonads o Secondary Sexual Traits – non-sexual but related to mating and rearing of youngs ▪ developed breast in human female ▪ smaller body of male frogs Other Types of Variations o Continuous Variation: ▪ when the characteristic varies in small amounts between individuals ▪ height ▪ weight o Discontinuous Variation ▪ when there are no one in-between ▪ Ex. Tongue-rolling ▪ Sex CAUSES OF VARIATION • • • METHOD: PEDIGREE ANALYSIS (PEDIGREE SYMBOLS) Genes (Inherited) o sex determination o mental retardation o infant deformities Environment (Acquired) o physical deformities o obesity Causes of Genetic Variation o Gene Mutation o Gene Flow - migration of gene from 1 population to another o Sexual Reproduction LESSON 3 - UNDERSTANDING THE OTHER FIELDS OF GENETICS TRANSMISSION GENETICS / CLASSICAL GENETICS • • deals with heredity and variation Methods: o Planned Experimental/Cross Breeding o Pedigree Analysis METHOD: PLANNED EXPERIMENTAL BREEDING • Mendel’s Experiments o Garden pea (Pisum sativum) is ideal for genetic study o Chose true-breeding/pure breeding which is between homozygous garden peas for his experiments o Mendel first worked with single-character crosses (Monohybrid cross). o The picture shows the technique of Mendel. o Discuss the technique step by step. o Why did Mendel use garden pea for his experiments? o Results: ▪ First filial generation offspring (F1) o o o • Sample Pedigree • Let’s analyze this.. CYTOGENETICS Pea Characters • • • • study the genes in the cell particularly in the chromosome provide the chromosomal basis of sex determination explain the distribution of boys and girls in the family Karyotyping = karyogram MOLECULAR GENETICS • • investigate in detail the nature of genetic material, it’s structure, mode of replication and how it acts to produce the phenotype DNA – genetic material • • POPULATION GENETICS • • • • • genetic structure of a population patterns of genetic variation in populations changes in genetic structure through time Describing genetic structure o genotype frequencies o allele frequencies o Ex: GMO (transgenic) organisms o plants with resistance to some insects o plants that can tolerate herbicides o crops with modified oil content. Recombinant DNA Technique and Gene Cloning o DNA fragments are cut out of their normal position in the chromosome using restriction enzymes and then inserted into other chromosomes or DNA molecules using enzymes Human Genome Project Application: o So what if there would be a database for the Human Genome?!? o Amelogenesis imperfecta ▪ This condition causes teeth to be unusually small, discolored, pitted or grooved, and prone to rapid wear and breakage ▪ CAUSE: Mutation in the AMELX, ENAM, and MMP20 genes ▪ TREATMENT: Crowning for the soft enamel ▪ In case of worse scenario, teeth may have to be extracted and implants or dentures are required LESSON 4 - THE HISTORY OF GENETICS • The interest of man on traits or features of organisms and how the traits were transmitted in generations started as early as 600 years ago. Since then till now, there are breakthroughs which are considered as milestones in its development. HISTORY OF GENETICS 6000 YEARS AGO • • APPLIED GENETICS • • • • • • • practical applications of Genetics Animal husbandry & plant breeding - to produce high yielding varieties of food crops like disease-resistant plants and varieties of cows and pigs Epidemiological Genetics – for better therapy, management and prevention of recurrence of inherited disease Eugenics – choice of partners for marriage and have an estimate of the likelihood of appearance of desirable trait Medicolegal Genetics – to solve legal problems like dispute in paternity and exchange of babies in the hospital nursery Genetic Counseling – for deciding abortion and planning responsible parenthood through amniocentesis Genetic Engineering - repair of defective genes the process of manually adding new DNA to an organism • As far back as 6,000 years ago, records of pedigrees of some domesticated animals and some crop plants were kept. Examples of domesticated animals: horses, dogs, camels, sheeps, and others Examples of cultivated plants: wheat, rice, maize–corn, date palm, and other herbal plants PREHISTORIC • The Greek Influence. 400 B.C. o Hippocrates ▪ The Hippocratic treatise: On the Seed. ▪ Male seed is thicker or more solid while the female is more fluid. o Aristotle & Pythagoras “Fluids & Vapors” Theory (500 BC) ▪ Aristotle: The vital heat fluid–SEMEN • Semen was regarded as highly purified blood. ▪ Pythagoras: Vapors were from various organs unite to form individuals. ERA OF AWAKENING • • • • • • • • • 17th Century : The Theory of Preformation o Jan Swammerdam – Dutch scientist: ▪ He theorized that sex cells contain a complete miniatures of an adult, perfect in every form, called a “homunculus” o William Harvey and Epigenesis ▪ An organism is derived from substances present in the egg that differentiate into adult structure during embryonic development 18th Century o Casper Wolff – German scientist who disapproved the Theory of Preformation. ▪ He offered experimental evidence that no preformed embryo existed in egg of the chicken. 18th Century: The Particulate Inheritance Theory o Pierre Louis Maupertuis ▪ He proposed that minute particles, one from each body part, united in sexual reproduction to form a new individual. 19th Century o The Theory of Pangenesis, Charles Darwin: 1859 ▪ He noted that each part of the body produced minute particles “gemmules”or “pangenes” which were contained in the blood of the entire body but eventually concentrated in reproductive organs. ▪ The individual represents “blending” of both parents and acquired characters would be inherited, too. o August Weismann: German biologist ▪ He disapproved the Theory of Pangenesis ▪ His experiment was the ▪ 22nd generation of mice where the tails of the parents were cut. Need to prove the absence of tails to offspring. ▪ Findings: The new lot of offspring consisted of tails. Gregor Mendel: “The Father” (1866) o The father of modern genetics o Used statistics to explain genetic events o Four Postulates: ▪ Unit Factors in Pairs ▪ Dominance/ Recessiveness ▪ Segregation ▪ Independent Assortment Friedrich Miescher: 1869 o DNA (first called "nuclein") is identified by Friedrich Miescher as an acidic substance found in cell nuclei. The significance of DNA is not appreciated for over 70 years. William Bateson: 1905 o The word "genetics" is coined by William Bateson. Quantitative traits in broad beans experiment 19031909 o First experiments on quantitative traits in broad beans by Wilhelm Johanssen and in wheat by Herman Nilsson-Ehle Thomas Morgan and the white eyes o genes are carried on chromosomes and the mechanical basis for heredity. o conducted the experiments on Drosophila (fruit flies) o The phenomenon of crossing over. • Eugenics Movement o 1910's-30's The eugenics movement is popular, fueling racist sentiment and leading to involuntary sterilization laws MODERN GENETICS MOLECULAR GENETICS • Transformation o 1928 Some component of heat-killed virulent bacteria can "transform" a non-virulent strain to become virulent, as shown by Fred Griffith. This sets the stage for work done in 1944. • • DNA is the genetic material Karl Landsteiner and the ABO Blood types • Genetic Recombination o 1931 - Genetic recombination is caused by a physical exchange of chromosomal pieces, as shown in corn by Harriet Creighton and Barbara Mcclintock. One gene: One protein o 1941 - One gene encodes one protein, as described by Beadle and Tatum Erwin Chargaff. 1950 o In DNA, there are equal amounts of A and T, and equal amounts of C and G, as shown by Erwin Chargaff. o However, the A+T to C+G ratio can differ between organisms. Hershey and Chase: The Blender Experiment o 1952 DNA is the molecule that mediates heredity, as shown in bacteriophage labeling experiments by Alfred Hershey and Martha Chase. • • • • • • DNA is Double Helix. 1953 o 1953 - DNA is in the shape of a double helix with antiparallel nucleotide chains and specific base pairing. This was deduced by Watson and Crick, who used Rosalind Franklin's data provided by Maurice Wilkins DNA is semi - conservative o 1958 - DNA replication is semi-conservative, as shown by Meselson and Stahl using equilibrium density gradient centrifugation. Restriction Enzyme o 1970 The first restriction enzyme is purified by Hamilton Smith. • Recombinant DNA Technology o 1972-73 Recombinant DNA is first constructed by Cohen and Boyer • DNA Sequencing Technology o 1977 - DNA sequencing technology is developed by Fred Sanger. Quest for the Genomes: Challenge for Modern Genetics o 1990's Genome projects are begun. The yeast genome is complete in 1996, and the C. elegans genome is done in 1998. o 1990's DNA microarrays are invented by Pat Brown and colleagues. o 1990's DNA fingerprinting, gene therapy, and genetically modified foods come onto the scene. o 1995 Automated sequencing technology allows genome projects to accelerate. o 1996-7 The first cloning of a mammal (Dolly the sheep) is performed by Ian Wilmut and colleagues, from the Roslin institute in Scotland. o 2000 The Drosophila genome is completed. The Arabidopsis genome is completed. The human genome is reported to be completed. o 2001 The sequence of the human genome is released, and the "post-genomic era" officially begins. o 2009 Controversies continue over human and animal cloning, research on stem cells, and genetic modification of crops. o •