* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ch 5 Powerpoint
Survey
Document related concepts
Nutriepigenomics wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Public health genomics wikipedia , lookup
Population genetics wikipedia , lookup
Genomic imprinting wikipedia , lookup
History of genetic engineering wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Genome (book) wikipedia , lookup
Designer baby wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Microevolution wikipedia , lookup
Behavioural genetics wikipedia , lookup
Transcript
Chapter 5 Are You Only as Smart as Your Genes? Mendelian and Quantitative Genetics Fourth Edition BIOLOGY Science for Life | with Physiology Colleen Belk • Virginia Borden Maier © 2013 Pearson Education, Inc. Copyright © 2009 Pearson Education, Inc. PowerPoint Lecture prepared by Jill Feinstein Richland Community College 1 The Inheritance of Traits Offspring resemble their parents, but not exactly. Siblings resemble each other, but not exactly. How much is because of environment? How much is inherited? © 2013 Pearson Education, Inc. 1 The Inheritance of Traits The human life cycle: Adults produce gametes in their gonads by meiosis. Sperm cells fertilize egg cells to form single-celled zygotes. Repeated cell divisions form the embryo. © 2013 Pearson Education, Inc. 1 The Inheritance of Traits The human life cycle, cont.: The embryo grow to become a fetus. After birth, the individual continues to grow until reaching adulthood. © 2013 Pearson Education, Inc. 1 The Inheritance of Traits Genes are segments of DNA that code for proteins. Analogous to words in an instruction manual for building a human Chromosomes are analogous to pages in the instruction manual. Each “page” contains thousands of “words” Different types of cells use different words, in different orders © 2013 Pearson Education, Inc. 1 The Inheritance of Traits - Producing Diversity in Offspring Mistakes in copying DNA (mutations) produce different versions of genes (alleles), with different results. © 2013 Pearson Education, Inc. 1 The Inheritance of Traits - Producing Diversity in Offspring Parent cell has two complete copies of the manual: 23-page copy from mom and 23-page copy from dad 23 pairs of homologous chromosomes © 2013 Pearson Education, Inc. 1 The Inheritance of Traits - Producing Diversity in Offspring Segregation: in meiosis, one member of each homologous pair goes into a gamete Gamete gets just one copy of each page of the manual Independent assortment randomly determines which member of a pair of chromosomes goes into a gamete This is due to random alignment during metaphase I About 8 million different combinations of chromosomes. © 2013 Pearson Education, Inc. 1 The Inheritance of Traits - Producing Diversity in Offspring Due to independent assortment, the instructions in one sperm cell is an unique combination of pages. © 2013 Pearson Education, Inc. 1 The Inheritance of Traits - Producing Diversity in Offspring Random fertilization produces more diversity: 64 trillion possibilities! No two humans are genetically identical, except for monozygotic twins. Dizygotic twins are 50% identical just like siblings born at different times. © 2013 Pearson Education, Inc. 2 Mendelian Genetics: When the Role of Genes Is Clear Gregor Mendel: first to accurately describe rules of inheritance for simple traits His research involved controlled mating between pea plants. His pattern of inheritance occurs primarily in traits that are due to a single gene with a few alleles. Mendel’s principles also apply to many genetic diseases in humans. © 2013 Pearson Education, Inc. 2 Mendelian Genetics: When the Role of Genes Is Clear Phenotype: physical traits of an individual Genotype: description of the alleles for a particular gene in an individual Homozygous (-ote): both alleles for a gene are identical Heterozygous (-ote): the gene has two different alleles Recessive: the phenotype of an allele is seen only when homozygous Dominant: the phenotype is seen when homozygous or heterozygous © 2013 Pearson Education, Inc. 2 Mendelian Genetics - Genetic Diseases in Humans Cystic fibrosis: a recessive human genetic disease Defect in chloride ion transport Causes recurrent lung infections, dramatically shortened lifespans Heterozygotes (carriers) do not show the symptoms Most common recessive disease among Europeans © 2013 Pearson Education, Inc. 2 Mendelian Genetics - Genetic Diseases in Humans Huntington’s disease: a dominant human genetic disease Progressive, incurable, always fatal Symptoms occur in middle age Mutant protein forms clumps inside nerve cell nuclei, killing the cells Having a normal allele cannot compensate for this © 2013 Pearson Education, Inc. 2 Mendelian Genetics - Using Punnett Squares to Predict Offspring Genotypes Punnett square: graphic way to predict possible outcomes of a cross Consider a cross between two cystic fibrosis carriers “F” = normal allele; “f” = recessive disease allele The cross would be: F f x F f What offspring could result? © 2013 Pearson Education, Inc. 2 Mendelian Genetics - Using Punnett Squares to Predict Offspring Genotypes © 2013 Pearson Education, Inc. Animation: Mendel’s Experiments Click “Go to Animation” / Click “Play” © 2013 Pearson Education, Inc. 2 Mendelian Genetics - Using Punnett Squares to Predict Offspring Genotypes Dihybrid crosses are crosses that involve two traits. The first step in a dihybrid is to determine the possible gametes. Yellow (Y) is dominant to green (y) and Round (R) is dominant to wrinkled (r). If you cross YyRr x YyRr, Possible gametes for parent 1 are YR, Yr, yR, yr Possible gametes for parent 2 are YR, Yr, yR, yr © 2013 Pearson Education, Inc. 2 Mendelian Genetics - Using Punnett Squares to Predict Offspring Genotypes The results of the cross results in a 9:3:3:1 phenotypic ratio. © 2013 Pearson Education, Inc. 3 Quantitative Genetics: When Genes and Environment Interact Quantitative traits show continuous variation: Large range of phenotypes E.g., height, weight, intelligence Variation due to both genetic and environmental differences © 2013 Pearson Education, Inc. 3 Quantitative Genetics: When Genes and Environment Interact Mean: sum up all the phenotypic values and divide by the number of individuals; same as the average. Variance: a measure of how much variability there is in the population © 2013 Pearson Education, Inc. 3 Quantitative Genetics - Why Traits Are Quantitative Quantitative traits, with continuous variation, are polygenic traits. Result of several genes Each with more than one allele Interaction of multiple genes with multiple alleles results in many phenotypes. Example: human eye color Heritability: proportion of the variation within a population due to genetic differences among individuals © 2013 Pearson Education, Inc. 3 Quantitative Genetics - Calculating Heritability in Human Populations Have to use correlation to measure heritability in humans Scientists seek “natural experiments,” situations in which either the overlap in genes or environment is removed Twins are often used Monozygotic twins share all their genes and their environment Dizygotic twins share environment, but only half their genes Heritability of IQ from such twin studies estimated to be about 0.52 © 2013 Pearson Education, Inc. 3 Quantitative Genetics - Calculating Heritability in Human Populations Twins share a more similar environment than most humans Similar treatment of twins might explain why their IQs are so similar Monozygotic twins raised apart share all genes but are treated like everyone else Estimates of IQ heritability for such twins is 0.72 Drawback: limited number of such twins to study Table 7.2 discusses IQ heritability © 2013 Pearson Education, Inc. 4 Genes, Environment, and the Individual The Use and Misuse of Heritability Differences between groups may be environmental, despite a high heritability A heritability value pertains just to the population in which it was measured, and to the environment of that population Imagine a laboratory population of mice of varying weights Divide this population into 2 genetically identical groups Give one group a rich diet, the other a poor diet The “rich diet” mice will be bigger than the “poor diet” mice. © 2013 Pearson Education, Inc. 4 Genes, Environment, and the Individual The Use and Misuse of Heritability Allow the mice in each group to breed, maintaining their diets. Measure the weight of adult offspring; correlation with parents shows high heritability. © 2013 Pearson Education, Inc. 4 Genes, Environment, and the Individual The Use and Misuse of Heritability Instead of body weight in mice, consider IQ in humans. Affluent group: higher IQs Impoverished group: lower IQs Conclude that the difference is probably due to genetics? © 2013 Pearson Education, Inc. 4 Genes, Environment, and the Individual The Use and Misuse of Heritability A highly heritable trait can still respond to environmental change. Maze-learning ability is highly heritable in rats. Bright rats have bright offspring Dull rats have dull offspring Still, no rats learned well in a restricted environment. All rats learned better in an enriched environment. © 2013 Pearson Education, Inc. 4 Genes, Environment, and the Individual The Use and Misuse of Heritability Heritability does not tell us about individual differences. Heritability is based on variances in populations. High heritability value for a trait does not automatically mean that most of the difference between two individuals is genetic. © 2013 Pearson Education, Inc. 4 Genes, Environment, and the Individual How Do Genes Matter? Genes have a strong influence on even complex traits. But, independent assortment of multiple genes with multiple alleles produces a large number of phenotypes. Environment can also have big effects. For quantitative traits, it is difficult to predict the phenotype of children from the phenotypes of the parents. © 2013 Pearson Education, Inc. Genes are segments of DNA that code for ________. proteins centromeres carbohydrates karyotypes © 2013 Pearson Education, Inc. Genes are segments of DNA that code for ________. proteins centromeres carbohydrates karyotypes © 2013 Pearson Education, Inc. Genes are comparable to________. words in an instruction manual pages in an instruction manual copy of pages in an instruction manual appendix in an instruction manual © 2013 Pearson Education, Inc. Genes are comparable to________. words in an instruction manual pages in an instruction manual copy of pages in an instruction manual appendix in an instruction manual © 2013 Pearson Education, Inc. Which of these events does not contribute to unique combinations of alleles? mutations independent assortment random fertilization cell cycle checkpoints © 2013 Pearson Education, Inc. Which of these events does not contribute to unique combinations of alleles? mutations independent assortment random fertilization cell cycle checkpoints © 2013 Pearson Education, Inc. True or False: Monozygotic twins occur when two separate eggs fuse with different sperm. True. False. © 2013 Pearson Education, Inc. True or False: Monozygotic twins occur when two separate eggs fuse with different sperm. True. False. © 2013 Pearson Education, Inc. A pea plant has one recessive allele for wrinkled seeds and one dominant allele for smooth seeds. What will the pea plant look like? wrinkle smooth half wrinkled, half smooth not enough information to tell © 2013 Pearson Education, Inc. A pea plant has one recessive allele for wrinkled seeds and one dominant allele for smooth seeds. What will the pea plant look like? wrinkle smooth half wrinkled, half smooth not enough information to tell © 2013 Pearson Education, Inc. Two heterozygotes mate. What are the odds that their offspring will be homozygous recessive? 100% 75% 50% 25% © 2013 Pearson Education, Inc. Two heterozygotes mate. What are the odds that their offspring will be homozygous recessive? 100% 75% 50% 25% © 2013 Pearson Education, Inc. Which trait is a quantitative trait that does not show continuous variation? height skin color presence or absence of a widow’s peak intelligence © 2013 Pearson Education, Inc. Which trait is a quantitative trait that does not show continuous variation? height skin color presence or absence of a widow’s peak intelligence © 2013 Pearson Education, Inc. Does nature or nurture play a bigger role in determining who we are? nature nurture they both play a large role © 2013 Pearson Education, Inc. Does nature or nurture play a bigger role in determining who we are? nature nurture they both play a large role © 2013 Pearson Education, Inc. The Punnett square shown here illustrates the outcome of a cross between a man who carries a single copy of the dominant Huntington’s disease allele and an unaffected woman. What are the odds that Huntington’s disease will not be passed to this offspring? 100% 75% 50% 25% © 2013 Pearson Education, Inc. The Punnett square shown here illustrates the outcome of a cross between a man who carries a single copy of the dominant Huntington’s disease allele and an unaffected woman. What are the odds that Huntington’s disease will not be passed to this offspring? 100% 75% 50% 25% © 2013 Pearson Education, Inc. This Punnett square illustrates the likelihood that a woman who carries the cystic fibrosis allele would have a child with cystic fibrosis if the sperm donor were also a carrier. What are the odds that this offspring will have cystic fibrosis? 100% 75% 50% 25% © 2013 Pearson Education, Inc. This Punnett square illustrates the likelihood that a woman who carries the cystic fibrosis allele would have a child with cystic fibrosis if the sperm donor were also a carrier. What are the odds that this offspring will have cystic fibrosis? 100% 75% 50% 25% © 2013 Pearson Education, Inc.