Chapter 1The Science of Genetics

Pit Bull Tree Scientists make a pit bull tree that can defend itself in the rain forest.

Ugly Flower Pollination Pretty flower worries that shell be pollinated by an ugly flower.

Supermans Sons Eyes Supermans son inherited his x-ray vision and sees pink underwear.

Babys Mickey Mouse Ears Baby mouses round ears reveal mothers relationship with Mickey Mouse.

Chapter Outline

Three Great Milestones in GeneticsDNA as the Genetic MaterialGenetics and EvolutionLevels of Genetic AnalysisGenetics in the World: Applications of Genetics to Human Endeavors

Three Great Milestones in GeneticsGregor Mendel: the rules of inheritanceJames Watson and Francis Crick: the structure of DNAThe Human Genome Project: the detailed analysis of human DNA

Mendel: Genes and theRules of Inheritance (1866)Geneshereditary factors responsible for traitsAllelesdifferent forms of genesRules of InheritanceAlleles of the same gene separate during gamete formationAlleles of different genes are inherited independently

What is a Gene?Genes are made of nucleic acidsNucleic acids are made of building blocks called nucleotidesNucleotides have three componentsSugar molecule (ribose or deoxyribose)Phosphate moleculeNitrogen-containing molecule (adenine, guanine, cytosine, thymine, uracil)RNA is ribonucleic acidDNA is deoxyribonucleic acid

Watson and Crick:The Structure of DNA (1953)Nucleotides are linked in a chain through sugar-phosphate interactionsDNA molecules are made of two chains of nucleotides wound around each other in a helixBase pairs hold the chains togetherA pairs with TG pairs with C

The Human Genome Project:Sequencing DNA and Cataloguing GenesGenomethe collection of DNA molecules that is characteristic of an organismGenomics is the analysis of DNA sequences that make up a genomeGenomics involves DNA sequencing technology, robotics, and computer scienceThe Human Genome Project determined the sequence of nucleotides in the DNA of the human genome

A Milestone in Genetics:X174, the First DNA Genome SequencedX174 is a virus that has single-stranded DNA as its genetic material.Frederick Sanger sequenced the genome of X174 in 1977

Key PointsGregor Mendel postulated the existence of particular factorsnow called genesto explain how traits are inherited.Alleles, the alternate forms of genes, account for heritable differences among individuals.James Watson and Francis Crick elucidated the structure of DNA, a macromolecule composed of two complementary chains of nucleotides.

Key PointsDNA is the hereditary material of all life forms except some types of viruses, in which RNA is the hereditary material.The Human Genome Project determined the sequence of nucleotides in the DNA of the human genome.Sequencing the DNA of a genome provides the data to identify and catalogue all the genes of an organism.

DNA as the Genetic MaterialInformation flows from DNA to RNA to protein.In all cellular organisms, the genetic material is DNA.The genetic materialMust be able to replicateMust contain informationMust be able to change

DNA Replication

DNA ReplicationBased on the complementary nature of the two strands of duplex DNA molecules.When the two parental strands are separated, the separated strands can serve as template for the synthesis of new strands.New strands are assembled by incorporating nucleotides according to base-pairing rules.At the end of replication, each template strand is paired with a newly synthesized partner strand.DNA replication is catalyzed by enzymes.

Gene Expression:Using Genetic Information

Gene ExpressionDuring transcription, an RNA molecule is synthesized from a DNA template.This messenger RNA (mRNA) molecules contains the information needed to synthesize a polypeptide.During translation, the triplet codons in the RNA specify the incorporation of particular amino acids into a polypeptide chain.

The ProteomeProteomethe collection of all the different proteins in an organism.Humans have between 20,000 and 25,000 genes in the genome and hundreds of thousands of proteins in the proteome.Proteomicsthe study of all the proteins in cells.

The Central Dogma of Molecular BiologyThe flow of information is DNA RNA protein.Some viruses can use RNA as a template for the synthesis of DNA in reverse transcription.Many genes do not encode polypeptides; their end-products are RNA molecules.

Mutation:Changing Genetic Information

Key PointsWhen DNA replicates, each strand of a duplex molecule serves as the template for the synthesis of a complementary strand.When genetic information is expressed, one strand of a genes DNA duplex is used as a template for the synthesis of a complementary strand of DNA.For most genes, RNA synthesis (transcription) generates a molecule (the RNA transcript) that becomes a messenger RNA (mRNA).

Key PointsCoded information in an mRNA is translated into a sequence of amino acids in a polypeptide.Mutations can alter the DNA sequence of a gene.The genetic variability created by mutation is the basis for biological evolution.

Genetics and EvolutionVariation in the DNA sequence makes it possible for species to evolve over time.Organisms with similar DNA sequences are descended from a common ancestor.

A phylogenetic treeA phylogenetic tree, or phylogeny, represents the historical relationships among organisms.

Key PointsEvolution depends on the occurrence, transmission, and spread of mutant genes in groups of organisms.DNA sequence data provide a way of studying the historical process of evolution.

Still Not Convinced About Evolution?

Basic Features of Genetic Engineering

BASIC FEATURES OF GENETIC ENGINEERINGWhat is genetic engineering? Genetic engineering is the process of manually adding new DNA to an organism. The goal is to add one or more new traits that are not already found in that organism. Examples of genetically engineered (transgenic) organisms currently on the market include plants with resistance to some insects, plants that can tolerate herbicides, and crops with modified oil content.

TO UNDERSTAND GENETIC ENGINEERINGCONCEPT #1: What is DNA? DNA is the recipe for life. DNA is a molecule found in the nucleus of every cell and is made up of 4 subunits represented by the letters A, T, G, and C. The order of these subunits in the DNA strand holds a code of information for the cell. Just like the English alphabet makes up words using 26 letters, the genetic language uses 4 letters to spell out the instructions for how to make the proteins an organism will need to grow and live.

TO UNDERSTAND GENETIC ENGINEERINGCONCEPT #2: Why are proteins important? Proteins do the work in cells. They can be part of structures (such as cell walls, organelles, etc). They can regulate reactions that take place in the cell. Or they can serve as enzymes, which speed-up reactions. Everything you see in an organism is either made of proteins or the result of a protein action.

1.4 TO UNDERSTAND GENETIC ENGINEERINGCONCEPT #3: How is DNA important in genetic engineering? DNA is a universal language, meaning the genetic code means the same thing in all organisms. It would be like if all cookbooks around the world were written in a single language that everyone knew. This characteristic is critical to the success of genetic engineering. When a gene for a desirable trait is taken from one organism and inserted into another, it gives the recipient organism the ability to express that same trait.

TO UNDERSTAND GENETIC ENGINEERINGHow is genetic engineering done? Genetic engineering, also called transformation, works by physically removing a gene from one organism and inserting it into another, giving it the ability to express the trait encoded by that gene. It is like taking a single recipe out of a cookbook and placing it into another cookbook.

Genetics in the World:Applications of Genetics to Human EndeavorsGenetics is relevant in many venues outside the research laboratory.

Genetics in Agriculture:Selective Breeding

Genetics in Agriculture:Genetically Modified OrganismsGenetically Modified Organisms (GMOs) are have been altered by the introduction of foreign genes.

Genetics in MedicineInborn Errors of Metabolism are metabolic abnormalities caused to mutant alleles.Genetic Counselors advise people about inheritance of genetic diseases.Molecular geneticsnew ways to detect mutant alleles.new ways to treat diseases.

Genetics in SocietyEconomic impactbiotechnology industry, pharmaceutical industry.Legal impactpaternity testing, forensics, identificationPhilosophical impact

Key PointsDiscoveries in genetics are changing procedures and practices in agriculture and medicine.Advances in genetics are raising ethical, legal, political, social, and philosophical questions.

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