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PowerPoint Presentation Materials to accompany Genetics: Analysis and Principles Robert J. Brooker CHAPTER 1 OVERVIEW OF GENETICS Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display INTRODUCTION • Human Genome Project? – Formally launched in 1990 – Aimed to decode our GENOME-all of the DNA found within all of our chromosomes Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-2 INTRODUCTION • A “working draft” of the human genome sequence was completed in 2000 – Nearly 3 billion nucleotides – 25000 of genes • The study of the human genome provides fundamental molecular details Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-3 INTRODUCTION • The knowledge gained from the Human Genome Project will lead to improvements in the diagnosis, treatment and prevention of disease Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-5 Figure 1.1b 1-6 Figure 1.1a 1-4 INTRODUCTION • While trying to understand genes and their function, scientists have developed many genetic technologies – DNA fingerprinting – Mammalian cloning Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-7 INTRODUCTION • DNA fingerprinting – Now a common tool of forensic science • Mammalian cloning – In 1997, Ian Wilmut and colleagues cloned the first mammal, A sheep named Dolly (Figure 1.2) • Cows, mice, goats, pigs and cats have now been cloned – Fears that the technology may be applied to humans led to legislative bans on human cloning Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-8 What about in our country? • Oyalı- First Turkish clonned baby lamb • 21 November 2007 First clonned sheep “Oyalı” • 30 March 2011 “Bahar” The lamb of Oyalı Human ? Hwang Woo-suk Seoul National University He announced that he has generated embriyonic stem cells via the embryonic clonning. INTRODUCTION • Genetic technologies allow the modification of animals in various ways • For example, mice can be made to glow green (Figure 1.3) – A jellyfish gene encoding a green fluorescent protein is introduced into lab mice – Upon exposure to ultraviolet light, the mice emit a bright green color Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-9 1.1 THE RELATIONSHIP BETWEEN GENES AND TRAITS • Genetics is the study of heredity and variation – It is the unifying discipline in biology • The central theme in genetics is the gene – The gene is classically defined as a ‘unit’ of heredity – The modern definition is a segment of DNA that produces a functional product such as a polypeptide. – Genes provide traits of an organism Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-10 Figure 1.4 Nucleotide building blocks are used to make long strands of DNA which associate with proteins and form chromosomes. The chromosomes are contained within the nucleus. 1-13 Each Cell Contains Many Different Proteins That Determine Cellular Structure And Function • The characteristics of a cell largely depend on the proteins it produces • Proteins have diverse biological functions Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-14 • Structural proteins – Tubulin • Aggregates to form microtubules • Plays role in cell shape and movement • Contractile proteins – Myosin • Plays role in muscle contraction • Hormonal proteins – Insulin • Regulates the level of glucose in the blood Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-15 • A particularly important group of proteins are the enzymes – Enzymes are biological catalysts – Catabolic enzymes • Involved in the breakdown of large molecules into smaller ones • Provide energy for the activities of the cell – Anabolic enzymes • Involved in the synthesis of large molecules from smaller ones • Provide components for the construction of the cell Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-16 DNA Stores the Information for Protein Synthesis • The genetic material in most living organisms is deoxyribonucleic acid (DNA) • DNA encodes the information required to synthesize all cellular proteins – It is able to do so because of its molecular structure Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-17 DNA Stores the Information for Protein Synthesis • DNA is a polymer of nucleotides – Each nucleotide contains one nitrogenous base • • • • Adenine (A) Thymine (T) Cytosine (C) Guanine (G) – The genetic information is stored in the linear sequence of these bases along the DNA molecule Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-18 DNA Stores the Information for Protein Synthesis • For example: • ATG GGC CTT AGC • Met Gly Leu Ser DNA Sequence Protein Sequence • TTT AAG CTT GCC • Phe Lys Leu Ala DNA Sequence Protein Sequence Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-19 • The DNA in living cells is contained within large structures termed chromosomes • Human cells have a total of 46 chromosomes • Each chromosome is a complex of DNA and proteins • An average human chromosome contains – More than a 100 million nucleotides – about 1,000 different genes 1-20 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Information Within the DNA Is Accessed During the Process of Gene Expression • Gene expression occurs in two steps – Transcription • The genetic information in DNA is copied into a nucleotide sequence of ribonucleic acid (RNA) – Translation • The nucleotide sequence in RNA is converted (using the genetic code) into the amino acid sequence of a protein Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-21 Figure 1.6 1-22 The Molecular Expression of Genes Within Cells Leads to an Organism’s Outwardly Visible Traits • A trait is any characteristic that an organism displays • We usually focus on Morphological traits – Affect the appearance of the organism – Example: The color of a flower • There are also Physiological traits – Affect the function of the organism – Example: Ability to metabolize a sugar • We can even identify Behavioral traits – Affect the ways an organism responds to the environment – Example: Mating calls of bird species Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-23 Inherited Differences in Traits Are Due to Genetic Variation • Genetic variation refers to differences in inherited traits among individuals within a population – For example: In petunias, white vs. purple flowers Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-26 • Genetic variation is a result of various types of changes at the molecular level – 1. Gene mutations • Small differences in gene sequences • Lead to two or more expression forms or alleles of the same gene – 2. Changes in chromosome structure • Large segments of the chromosome may be lost or duplicated – 3. Changes in chromosome number • Single chromosomes may be lost or gained – Refer to Figure 1.9a • A whole set of chromosomes may be inherited – Refer to Figure 1.9b Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-27 Wheat with 6n (3x2n) chr. Down Syndrome with 47 chr. Traits Are Governed by Genes and by the Environment • The traits an individual expresses often do not result from its genes alone • Rather, traits are a result of the interaction between genes and the environment – For example, an individual’s diet has an effect on his/her height and weight and even intelligence • In some cases, the environment dictates whether a disease is manifested in an individual or not Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-28 • Phenylketonuria (PKU) – Humans contain a gene encoding the enzyme phenylalanine hydroxylase • Converts phenylalanine to tyrosine – Humans with one or two functional copies of this gene can metabolize phenylalanine – Humans with two copies of a rare inactive allele cannot metabolize phenylalanine • Phenylalanine will thus accumulate • It ultimately causes a number of detrimental effects – Mental retardation, for example Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-29 Same but different Chris, left, and Xand van Tulleken have identical DNA but differing pain responses due to their life experiences Read more: http://www.dailymail.co.uk/health/article-1216253/Theyre-identical-twins--age-10-years-other.html#ixzz2fPzhq1V8 Follow us: @MailOnline on Twitter | DailyMail on Facebook During Sexual Reproduction, Genes Are Passed from Parent to Offspring • Gregor Mendel, in the mid-19th century, provided the foundation of the science of genetics Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-31 During Sexual Reproduction, Genes Are Passed from Parent to Offspring • Sexually-reproducing species are diploid – Have two copies of each chromosome • One from each parent – The two copies are termed homologues – Homologues contain the same genes • Not necessarily the same alleles Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-32 • In humans, most cells have 46 chromosomes – 23 homologous pairs Note: The X and Y chromosomes of human males are not homologous Figure 1.11 1-33 • Gametes – Sperm and egg cells – Are haploid – Have 23 chromosomes Figure 1.11 1-34 During Sexual Reproduction, Genes Are Passed from Parent to Offspring • The union of sperm and egg during fertilization restores the diploid number • Sexual reproduction enhances genetic variation – It results in combinations of traits not found in either parent Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-35 1.2 FIELDS OF GENETICS • Genetics encompasses four biological disciplines – – – – Molecular Cellular Organismal Population • It is traditionally divided into three areas – Transmission genetics – Molecular Genetics – Population Genetics Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-40 Transmission Genetics Explores the Inheritance Patterns of Traits as They Are Passed from Parents to Offspring • Transmission genetics is the oldest field of genetics • It examines how traits are passed from one generation to the next • The conceptual framework was provided by Gregor Mendel in the 1860s – Genetic determinants pass from parent to offspring as discrete units • These are now termed genes Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-41 Transmission Genetics Explores the Inheritance Patterns of Traits as They Are Passed from Parents to Offspring • The basic experimental approach is the genetic cross – Two selected individuals are mated – The traits in question are analyzed over several generations – Analysis is often quantitative in nature Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-42 Transmission Genetics Explores the Inheritance Patterns of Traits as They Are Passed from Parents to Offspring • Transmission genetics is covered in Chapters 2-8 – Chapter 2 • Mendelian patterns of inheritance – Chapter 3 • Chromosomes and their roles in inheritance – Chapters 4-8 • Complexities in transmission genetics – Linkage – Non-Mendelian patterns of inheritance Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-43 Molecular Genetics Seeks a Biochemical Understanding of the Hereditary Material • Molecular genetics is the most modern field of genetics • It deals with the molecular features of DNA and how these underlie gene expression – A genes features, organization and function – Detailed analysis of DNA, RNA and proteins Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-44 Molecular Genetics Seeks a Biochemical Understanding of the Hereditary Material • Molecular geneticists study “model organisms”, such as – Escherichia coli (a bacterium) – Saccharomyces cerevisiae (a yeast) – Drosophila melanogaster (an animal) – Arabidopsis thaliana (a plant) • The genes found in these organisms behave similarly as those in humans Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-45 Molecular Genetics Seeks a Biochemical Understanding of the Hereditary Material • Molecular geneticists typically employ the genetic approach to research – They study mutant genes that have an abnormal function • Example: Loss-of-function mutation Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-46 • Molecular genetics is covered in Chapters 9-23 – Chapters 9-15 • Structure, replication, expression and regulation of the genetic material – Chapters 16 and 17 • Mutations and rearrangements of the genetic material – Chapters 18-21 • Recombinant DNA technology and computer-based approaches to studying the genetic material – Chapter 22 • Role of the genetic material in human diseases – Chapter 23 • Role of the genetic material in development Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-47 Population Genetics Is Concerned With Genetic Variation and Its Role in Evolution • Population genetics deals with the genetic composition of populations and how it changes over time and space • It connects the work of Mendel on inheritance to that of Darwin on evolution Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-48 Population Genetics Is Concerned With Genetic Variation and Its Role in Evolution • Population genetics is covered in Chapters 24-26 – Chapter 24 • The role of the environment and genetics in the expression of traits – Chapter 25 • How and why some alleles are maintained in populations – Chapter 26 • The genetics behind the process of evolution Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display 1-49