PCB3063 Summer 2014 Chapter 1 Introduction to Genetics Introduction December 1998 deCODE Genetics was granted the right to access the medical records of 270 000 Icelandic residents to create a database They cross referenced this information with the Health Sector Database as well as the genealogical database from the National Archives Ended in 2012 Other large scale databases have developed in Great Britain Estonia Latvia and the Kingdom of Tonga Used to analyze human genes for susceptibility to diseases Iceland was selected due to the high level of genetic relatedness within its population which began 1000 years ago from Scandinavian and Celtic sources In addition the health care system is state supported which allows for good medical records Causes debates over privacy consent and commercialization 1 1 Genetics has a Rich and Interesting History Introduction Domestication of animals and cultivation of plants lends itself to the recognition of On the Seed by Hippocrates suggested that humors in the male parts of the body Aristotle proposed that the male semen contained vital heat which produced traits many years ago accounted for offspring s traits offspring similar to the parent 1600 1850 The Dawn of Modern Biology 1600s William Harvey proposed epigenesist in which an organism follows developmental events following fertilization of an egg Contradicts preformation the fertilized egg contains a miniature adult called a homunculus 1830 Matthias Schleiden and Theodor Schwann proposed cell theory organisms are composed of basic units called cells that are derived from similar preexisting structures Spontaneous generation creation of living organisms from non living components disproved by Louis Pasteur Charles Darwin and Evolution The Origin of Species published in 1859 by Darwin describing evolutionary ideas He believed existing species evolved over time from preexisting ones Natural selection the most favorable traits will be carried on explanation for mechanism of evolutionary change based on the observation of Alfred Russel Wallace that an environment has more organisms than it can support leading to competition individuals that can adapt and posses heritable traits survive Darwin lacked genetic knowledge of variation and inheritance 1 PCB3063 Summer 2014 Gregor Mendel published his paper on the inheritance of traits using pea plants in 1866 Showed how traits are inherited His research was not well known until 1900s Chromosomal theory of inheritance closed the gap in Darwin s theory heredity and development depend on genetic information in genes contained in chromosomes and passed on through gametes 1 2 Genetics progressed from Mendel to DNA in less than a century Mendel s Work on Transmission of Traits Pea plants decade long experiment Augustinian monk Showed that traits are passed from parents to offspring in predictable ways Genetics branch of biology concerned with heredity and variation Chromosome Theory of Inheritance Mendel and Meiosis 20 years after Mendel s work we discovered chromosomes Diploid number 2n number of chromosomes 46 in humans Homologous chromosomes chromosomes in diploid cells exist in pairs Haploid number n cells produced from meiosis only receive one chromosome from each pair chromosomes to parent pair Mitosis chromosomes copied each daughter cell receives identical set of Meiosis gamete formation cells receive one chromosome from each chromosome Walter Sutton and Theodor Boveri behavior of chromosomes in meiosis is similar to behavior of genes in gamete formation noted by Mendel Chromosome theory of inheritance inherited traits controlled by genes on chromosomes that are transmitted through gametes genetic continuity throughout generations Genetic Variation Drosophila melanogaster fruit fly used for studying inheritance of traits Mutation heritable change in DNA sequence source of genetic variation Allele alternative forms of a gene Phenotype observable features such as eye color Genotype set of alleles for a given trait Geneticist can map the location of a gene on the chromosome using mutations The Search for the Chemical Nature of Genes DNA or protein White eye mutation in fruit flies showed that he trait was on a single chromosome Proteins and DNA are major chemical components of chromosomes 1944 researchers at Rockefeller Institute showed that DNA carried genetic information in bacteria did not convince many scientists Further work on viruses proved that DNA not protein carried genetic information and scientists turned their attention toward deducing the structure 2 PCB3063 Summer 2014 1 3 Discovery of the Double Helix Structure of DNA and RNA 1953 James Watson and Francis Crick described structure of DNA along with Maurice Wilkins they received the Nobel Prize in 1962 Each linear strand of DNA is made up of nucleotides A adenine G guanine T thymine or C cytosine The two strands of DNA are complements of each other AT and CG are pairs RNA contains ribose instead of deoxyribose in DNA Gene Expression Phenotype is expressed as a result of the order of the nucleotides in DNA through a series of steps Transcription in eukaryotes one strand of DNA is used to construct a complementary strand of RNA That RNA molecule moves to the cytoplasm where the mRNA binds to the ribosome Translation the synthesis of proteins under the instruction of mRNA Genetic code the information encoded in the mRNA series of nucleotide triplets called codons There are 20 different amino acids found in proteins TRNA transfer RNA assembles proteins recognize the code in the RNA and carry the correct amino acids to construct the protein in translation Proteins and Biological Functions Proteins are end product of gene expression Diversity of life arises from proteins that are long and each position can be one of 20 amino acids Enzymes biological catalysts largest category of proteins allows cellular metabolism to happen at body temperature and lower activation energies Insulin pancreatic hormone Hemoglobin oxygen binding molecule in red blood cells Collagen connective tissue molecule Actin and Myosin contractile muscle proteins Linking Genotype to Phenotype Sickle Cell Anemia Caused by mutant form of hemoglobin A mutation in the beta globin causes a change in one DNA nucleotide change in codon 6 in mRNA GAG to GUC A person with two mutant copies of the genes has sickle cell anemia 1 4 Development of Recombinant DNA Technology Restriction enzymes used by bacteria to cut DNA of
View Full Document
Unlocking...