Human Genetics: Chapter 1 - The Information in a Human Genome PDF

Because learning changes everything. ® Chapter 1 The Information in a Human Genome Thirteenth Edition Ricki Lewis © 2021 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution pe...

Because learning changes everything. ® Chapter 1 The Information in a Human Genome Thirteenth Edition Ricki Lewis © 2021 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.  Learning Outcomes 1 1. Explain what genetics is and what it is not. 2. Distinguish among gene, exome, and genome. 3. Define bioethics. 4. List the levels of genetics. 5. Explain how DNA is maintained and how it provides the information to construct a protein. 6. Explain how a mutation can cause a disease. 7. State the basis of genetic diversity © McGraw Hill 2  Learning Outcomes 2 8. Explain the relationship between DNA and chromosomes. 9. Distinguish between Mendelian and complex traits. 10. Explain how genetics underlies evolution. 11. List some practical uses of DNA information. 12. Distinguish between traditional breeding and genetically modifying organisms. 13. Explain how investigating genomes extends beyond interest in ourselves. © McGraw Hill 3  Introduction Genetics is the study of inherited traits and their variations and transmission. It has recently exploded into a powerful source of information about our identities. Human genetics touches forensics, bioethics, psychology and even history Consumer genetics enables anyone to learn about their DNA © McGraw Hill 4  Consumer Genetics © McGraw Hill 5  What is Genetics? Genetics is a life science that should not be confused with genealogy Genetic genealogy examines how people are related. Heredity concerns the transmission of traits and biological information between generations. Certain difficult-to-define human characteristics might appear to be inherited if they affect several family members, but may reflect shared genetic and environmental influences. © McGraw Hill 6  The Vocabulary of Genetics Genes are the instructions to manufacture proteins, which determine inherited traits. Are composed of deoxyribonucleic acid (DNA). A genome is a complete set of genetic information. A cell, the basic unit of life, contains two genomes. The exome is the part of the genome that encodes protein. Genomics compares and analyzes the functions of many genes. Bioethics addresses issues and controversies that arise in applying medical technology and using genetic information. © McGraw Hill 7  The Levels of Genetics 1 Genetics considers the transmission of information at several levels. It begins with the molecular level and broadens through cells, tissues and organs, individuals, families, and finally to populations and the evolution of species. A DNA molecule resembles a spiral staircase or double helix © McGraw Hill 8  The Levels of Genetics 2 © McGraw Hill 9  Deoxyribonucleic Acid Components: Phosphate Sugar Base: Adenine (A) Thymine (T) Cytosine (C) Guanine (G) The information that a DNA molecule imparts is in the sequences of A, T, C, and G. The chemical structure of DNA gives it two key abilities essential for being the basis of life: Can replicate itself Is accessible to manufacture proteins © McGraw Hill 10  The DNA Double Helix DNA strands are antiparallel © McGraw Hill 11  From Gene to Protein 1 In DNA replication, a new double helix is formed from the old one using free DNA bases. Thus, the two “daughter” cells inherit identical copies of the genome during cell division. Transcription copies the DNA information into a related molecule called messenger ribonucleic acid (RNA) This process is also called gene expression Translation uses the information in RNA to assemble amino acids into proteins. Proteins provide the traits associated with genes. © McGraw Hill 12  From Gene to Protein 2 © McGraw Hill 13  Mutations A change in a gene is a mutation, and it can have an effect at the whole-person level Alleles are variants of genes Are inherited or arise by mutations Mutations in sperm or egg cells are passed on to the next generation Mutations may be positive, negative, or neutral © McGraw Hill 14  Cystic Fibrosis 1 The disease cystic fibrosis (CF) illustrates how a missing or abnormal protein causes the symptoms of an inherited disease In CF, the protein is the cystic fibrosis transmembrane conductance regulator (CFTR). The functioning protein works like a selective doorway in cells lining the airways and other parts Can cause thickening secretions when it doesn’t work properly © McGraw Hill 15  Cystic Fibrosis 2 © McGraw Hill 16  Mutation of Cystic Fibrosis 1 The disease cystic fibrosis is caused by a mutation in the CFTR gene. The mutation causes the replacement of the amino acid glycine with aspartic acid at a specific site. This alters the CFTR protein, so that it cannot open at the cell’s surface Difficulty breathing, impaired digestion, and other symptoms result © McGraw Hill 17  Mutation of Cystic Fibrosis 2 © McGraw Hill 18  Chromosomes and More Chromosomes consist of DNA and protein. When a cell is not dividing, the chromosomes are unwound and in a structure called the nucleus. A somatic cell in humans has 23 chromosome pairs. 22 pairs of autosomes A pair of sex chromosomes Females have two X chromosomes Males have one X and a Y Karyotypes display the chromosome pairs from largest to smallest © McGraw Hill 19  Karyotype © McGraw Hill Kateryna Kon/Shutterstock 20  Traits A trait caused predominantly by a single gene is termed Mendelian Named for Gregor Mendel, who discovered the patterns of trait transmission. Most characteristics are complex traits They are determined by one or more genes and environmental factors The more factors that contribute to a trait or illness—inherited or environmental—the more difficult it is to predict the risk of occurrence in a particular family member © McGraw Hill 21  Mendelian versus complex traits © McGraw Hill (a): Lester V. Bergman/Getty Images; (b): Steve Mason/Getty Images 22  The Body: Cells, Tissues, and Organs A human body consists of approximately 30 trillion cells. Cells differ in appearance and activities because they use only some of their genes. Cells undergo differentiation, or specialization, of distinctive cell types. Stem cells divide to yield other stem cells and cells that differentiate. Tissues are groups of cells with a shared function. © McGraw Hill 23  Relationships: From Individuals to Families Genotype refers to the underlying DNA instructions (alleles present) Phenotype is the visible trait, biochemical change, or effect on health (alleles expressed). Alleles can be dominant (exerting an effect in a single copy) or recessive (requiring two copies for expression). Pedigrees are charts that depict the members of a family and indicate which individuals have particular inherited traits. © McGraw Hill 24  Pedigrees R Us © McGraw Hill 25  The Bigger Picture: From Populations to Evolution Above the family level of genetic organization is the population. In a strict biological sense, a population is a group of individuals that can have healthy offspring together. In a genetic sense, a population is a large collection of alleles, distinguished by their frequencies Genetic populations are defined by their collections of alleles, termed the gene pool. Genome comparisons among species reveal evolutionary relationships. © McGraw Hill 26  Applications of Genetics and Genomics Genetics is impacting several areas of our lives, from health care choices, to what we eat, to unraveling our pasts and guiding our futures. “Citizen scientists” are discovering genetic information about themselves while helping researchers compile genomic databases Thinking about genetics evokes fear, hope, anger, wonder, and despair, depending on context and circumstance. This has to do with how DNA information is used © McGraw Hill 27  Establishing Identity Comparing DNA sequences among individuals can rule out identity, relationships, or ancestry, or indicate the probability that two individuals are related. DNA profiling refers to the techniques, statistical analyses, and machine learning approaches used to compare DNA sequences between & among individuals. Used most often in the context of forensic science Also useful in identifying victims of natural disasters Another use is to analyse foods to determine authenticity of gourmet items © McGraw Hill 28  Illuminating History DNA analysis is a time machine of sorts. DNA evidence may confirm findings from anthropology and history or contradict it. DNA testing can provide views into past epidemics. Analysis of DNA in the mummy of the Egyptian king Tutankhamun revealed that the boy king likely died from complications of malaria and nothing else DNA analysis confirmed that president Thomas Jefferson had children with his slave Sally Hemings. Today the extended family holds reunions © McGraw Hill 29  DNA reveals and clarifies history © McGraw Hill Leslie Close/AP Photo 30  Conservation Genetics Combining analysis of genetic diversity with reproductive technologies creates a way to rebuild populations that are headed toward extinction. This is the case for the northern white rhinoceros of Africa. Researchers are working on ways to bring back the species by borrowing from the genomes of the subspecies to the south © McGraw Hill 31  Precision Medicine In several nations, people are volunteering to have their genomes sequenced so that researchers can learn more about health and disease. Evaluating genetic data is a large part of precision medicine, which is tailoring of treatments to individuals. The microbiome is the symbiotic relationship between an individual’s genome, diet, lifestyle factors, and the many microbes in the body. Pharmacogenetics considers gene variants to predict whether a specific drug will be effective or cause side effects in an individual. © McGraw Hill 32  Genetic Modification Genetic modification means altering a gene or genome in a way that does not occur in nature Genetically modified organisms (GMOs) and drugs have been available for many years. They arise from recombinant DNA technology, which adds a gene from a different species. A newer technology, genome editing, can replace, remove, or add specific genes into the cells of any organism. The most talked-about tool is CRISPR-Cas9 © McGraw Hill 33  Exome Sequencing Exome sequencing determines the order of the DNA bases of all parts of the genome that encode proteins. The information is compared to databases that list many gene variants (alleles) and their associations with specific phenotypes, such as diseases. Exome sequencing is valuable in identifying extremely rare diseases—swiftly. Used to be years – not a matter of hours! © McGraw Hill 34  Global Perspective on Genomes 1 We share the planet with many thousands of other species. Many of these we cannot grow in the lab Metagenomics is a field that involves sequencing all of the DNA in a habitat. Shows how species interact, and may yield new drugs and reveal novel energy sources The first metagenomics project described life in the Sargasso Sea. © McGraw Hill 35  Global Perspective on Genomes 2 Efforts are underway to limit “genetic prospecting” Genetics is a special branch of life science because it affects us intimately. Social issues that parallel scientific progress Equal access to genetic tests and treatments Misuse of genetic information Abuse of genetics to cause harm © McGraw Hill 36  Global Perspective on Genomes 3 Genetics and genomics are spawning technologies that may vastly improve the quality of life Human genome information has tremendous potential for the entire globe. World organizations are discussing how nations can share new diagnostic tests and therapeutics. Individual nations are adopting guidelines to use genetic information to suit their strengths. Bioethics discusses instances when genetic testing can affect privacy. © McGraw Hill 37