What is Genetics? Genetics Mapping of genes Basis of life Inheritable traits Abnormalities Disease Development DNA RNA Proteins Central dogma - Watson & Crick Genes- segments of DNA that code for proteins 3 billion bases in the human genome We should have 1.5 million genes o We actually only have about 24,000 genes in the human genome o About the same about of genes as a ring worm Genetics- is the study of all manifestation of inheritance from the distributions of traits to the molecules of the gene itself Prior to 1865- there were some discoveries that initiated our current understanding of science The development of the microscope and the discovery of the cell Cell Theory Rudolf Virchow (omnis cellula e cellula) and the discovery of the nucleus by Robert brown The work Charles Darwin first printed o Descent with modification o Survival of the fittest Adaptive capacity Pass on genetic materials Gregor Mendel published his work with the garden pea, Psium sativum in 1865 (the first rules of heredity) Mendels work went unknown until its simultaneous and independent rediscovery in 1900 by Hugo devries, Carl correns and Erich von Tschermak Flemming described the genetic unit (Chromosome) in the late 1800 s and by close of the century, both mitosis and meiosis were well described o Chrom- color o Some- body The early-mid 1900 s led to the understanding of chromosome interactions that led to mendels rules o Phenotype- traits that you can see o Genotype- genetic makeup leading to a trait
Chromosomal theory of inheritance Genes can be artificially mutated (mutations are then inherited) o Allows for laboratory results to tell us what is happening in nature Genes are located on chromosomes and with the mapping of fruit fly chromosomes (Alfred Sturtevant, 1913) the fact that genes are in linear order on a given chromosomes o Tells that they are read in a linear pathway Post WWII led to the development of molecular genetics o Anything before WWII we were looking at indirect phenotypic The discovery that DNA is the genetic material (Avery et al., 1944) ushered in this branch of science o Found that DNA was a salt holding in proteins James Watson and Francis Crick discovered the structure of DNA (1953) The advent of PCR (polymerase chain reaction) by Kerry Mullis (1987) which gave us a novel method of amplifying large amount of a specific piece of DNA. This is the revolution leading to the explosion of molecular biology 1990 s led to the initiation of the Human Genome Project (the draft was completed in 2000) Francis Collins Public Government funded Linear sequencing a very precise form o Takes a long time Craig venter Private Corporate funded Used shotgun sequencing o Really fast o Kerry Mullis Led the initiation of the human genome project draft was completed in 2000 The first sequenced genome was that of a yeast in 1992 o It was a little over 300,000 base pairs Dolly the sheep was cloned in 1997 o Cloned by somatic transferring o Take nucleus out of the egg o Put nucleus of a somatic skin cell into the now empty egg o Egg then thought it was a zygote Dolly was the first mammal cloned from an adult using modern techniques of transgenic cloning Recombinant DNA, GM organisms, patents, and epigenetics
Junk DNA - part of the genome that are changing due to the organisms environment How do we know? Why fruit flies and colon bacteria? Certain organisms exhibit traits that make them model organisms for study o Short generation times are essential to genetic research o Small size (manageable size) o Simple genome o Ample variation for test-crosses o Characteristics of a given organism may or may not be universal Genetics can be divided into 3 distinct areas Classical Molecular Evolutionary/ Population Classical- called Mendelain genetics Mendels principles, mitosis and meiosis, sex determination and linkage, chromosomal mapping and cytogenetics Major method used is crossing organisms Mutant lineages of organisms were identified and utilized in chromosome mapping exercises and cytogenetics Molecular: molecules Structure/ chemistry of DNA Transcription/ Translation Cloning and genomics Gene expression DNA mutation/ repair Extrachromosomal inheritance -DNA found in nucleus, mitochondria, chloroplasts and maybe centrioles -Chromosomes are only found in the nucleus Here lies the realm of PCR, gene sequencing and all modern stuff Is DNA the universal code of inheritance? Recombinant DNA (producing recombined hybrid plasmid genomes) Gene sequencing and cloning
Evolutionary: also called Quantative genetics Deals with the application of the Hardy-Weinberg model to populations, evolution and speciation Allele- alternate forms of genes Some genes may not have any alternate alleles Some genes may have thousands of alleles If you are diploid, you will have 2 alternate alleles in your body If you are haploid, you will only have 1 alternate H-W population o Large population size o No genes coming in or going out o No mutation o Random mating Allows us to use it as a base line in seeing what affects a change in allele frequency Evolution is the change in allelic frequencies in a population over time How do we figure these things out? Sequencing, either protein or gene sequences are compared throughout populations From an evolutionary standpoint, genes are compared among taxonomic levels to look for links between/among specific groups Genetics and Society? A Monk peas in the garden Mendels experiment: why the garden pea? The peas had discrete traits Short generation Ability to either self cross or cross pollinate They produced large numbers of off spring Pea characteristics Tall or short Flower or no flower
Mendel took years to create purebred peas for his experiments Homogenous, true breeding plants Adult plants were diploid (2N) o 1 chromosome from mom, 1 chromosome from dad In addition to direct lineage crosses o Mendel completed reciprocal crosses to show that results were independent of parental sex Monohybrid What did he see? Unit factors in pairs T T T t t Tt Tt T TT Tt t Tt Tt t Tt tt All F1 (Tall) F2: 3:1 phenotype 75%: 25% Genotype 1:2:1 Unit Factors, Dominance/Recessive leading to: The Rule of Segregation o Alleles (alternate form of a gene) segregate from each other to form gametes What about genotype and phenotype? Why is this important? All F2 dwarfs should produce only dwarf plants (homozygous recessive) 1/3 of the tall plants should be homozygous (homozygous dominant) 2/3 should be heterozygous (tall but heterozygous) Rules and segregation (from monohybrid cross) 1. Heritable factors- 2 per adult 2. Heritable factors segregate to form gametes 3. Gametes get 1 heritable factor per each adult 4. Dominant and recessive Dihybrid Round- R Wrinkled- r Yellow- Y Green- y Parent Round and yellow RRYY crossed with RRYY