* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download You Light Up My Life
Public health genomics wikipedia , lookup
Gene therapy of the human retina wikipedia , lookup
Gene nomenclature wikipedia , lookup
Point mutation wikipedia , lookup
Transgenerational epigenetic inheritance wikipedia , lookup
Genome evolution wikipedia , lookup
X-inactivation wikipedia , lookup
Genetically modified crops wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Behavioural genetics wikipedia , lookup
Pharmacogenomics wikipedia , lookup
History of genetic engineering wikipedia , lookup
Gene expression profiling wikipedia , lookup
Genome (book) wikipedia , lookup
Gene expression programming wikipedia , lookup
Human genetic variation wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Genomic imprinting wikipedia , lookup
Population genetics wikipedia , lookup
Heritability of IQ wikipedia , lookup
Genetic drift wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Designer baby wikipedia , lookup
Microevolution wikipedia , lookup
Observable Patterns of Inheritance Chapter 11 Earlobe Variation Whether a person has attached or detached earlobes depends on a single gene Attached earlobes: two copies of the recessive allele for this gene Detached earlobes: either one or two copies of the dominant allele Early Ideas about Heredity People knew that sperm and eggs transmitted information about traits Blending theory Problem: Would expect variation to disappear What would you expect to happen with trait such as height? Variation in traits persists Gregor Mendel Strong background in plant breeding and mathematics Using pea plants, found indirect but observable evidence of how parents transmit genes to offspring Genes Units of information about specific traits Passed from parents to offspring Each has a specific location (locus) on a chromosome Alleles Different molecular forms of a gene Arise by mutation Dominant allele masks a recessive allele that is paired with it Allele Combinations Homozygous having two identical alleles at a locus AA or aa Heterozygous having two different alleles at a locus Aa Genetic Terms A pair of homologous chromosomes Figure 11.4 Page 179 A gene locus A pair of alleles Three pairs of genes Figure 11.4 Page 179 Genotype & Phenotype Genotype refers to particular genes an individual carries Phenotype refers to an individual’s observable traits Cannot always determine genotype by observing phenotype Tracking Generations Parental generation mates to produce P First-generation offspring mate to produce F1 Second-generation offspring F2 Monohybrid Crosses Experimental intercross between two F1 heterozygotes AA X aa Aa (F1 monohybrids) Aa X Aa ? Mendel’s Monohybrid Cross Results F2 plants showed dominant-torecessive ratio that averaged 3:1 Figure 11.5 Page 180 5,474 round 1,850 wrinkled 6,022 yellow 2,001 green 882 inflated 299 wrinkled 428 green 152 yellow 705 purple 224 white 651 long stem 207 at tip 787 tall 277 dwarf Probability The chance that each outcome of a given event will occur is proportional to the number of ways that event can be reached Monohybrid Cross Illustrated True-breeding homozygous recessive parent plant F1 PHENOTYPES aa True-breeding homozygous dominant a parent plant Aa Aa Aa Aa a A Aa Aa A Aa Aa AA An F1 plant self-fertilizes and produces gametes: F2 PHENOTYPES Aa A AA Aa Aa aa a A AA Aa Figure 11.7 Page 181 a Aa aa Mendel’s Theory of Segregation An individual inherits a unit of information (allele) about a trait from each parent During gamete formation, the alleles segregate from each other Test Cross Individual that shows dominant phenotype is crossed with individual with recessive phenotype Examining offspring allows you to determine the genotype of the dominant individual Punnett Squares of Test Crosses Homozygous recessive a a Homozygous recessive a a A Aa Aa A Aa Aa a aa aa A Aa Aa Two phenotypes All dominant phenotype Dihybrid Cross Experimental cross between individuals that are homozygous for different versions of two traits Dihybrid Cross: F1 Results purple flowers, tall TRUEBREEDING PARENTS: AABB GAMETES: AB x white flowers, dwarf aabb AB ab ab AaBb F1 HYBRID OFFSPRING: Figure 11.9 (1) All purple-flowered, tall Dihybrid Cross: F2 Results AaBb X AaBb 1/4 AB 1/4 Ab 1/4 aB 1/4 AB 1/4 Ab 1/4 aB 1/4 ab 1/4 ab 1/16 AABB 1/16 AABb 1/16 AaBB 1/16 AaBb 1/16 AABb 1/16 AAbb 1/16 AaBb 1/16 Aabb 1/16 AaBB 1/16 AaBb 1/16 aaBB 1/16 aaBb 1/16 AaBb 1/16 Aabb 1/16 aaBb 1/16 aabb 9/16 purple-flowered, tall 3/16 purple-flowered, dwarf 3/16 white-flowered, tall 1/16 white-flowered, dwarf Figure 11.9(2) Page 183 Independent Assortment Mendel concluded that the two “units” for the first trait were to be assorted into gametes independently of the two “units” for the other trait Members of each pair of homologous chromosomes are sorted into gametes at random during meiosis Independent Assortment Metaphase I: A A a a B B b b OR A A a a b b B B Metaphase II: Gametes: A A a a A A a a B B b b b b B B B A B A 1/4 AB b a b a 1/4 ab b A b A 1/4 Ab B a B a 1/4 aB Impact of Mendel’s Work Mendel presented his results in 1865 Paper received little notice Mendel discontinued his experiments in 1871 Paper rediscovered in 1900 Dominance Relations Complete dominance Incomplete dominance Codominance Incomplete Dominance X Incomplete Homozygous Homozygous parent parent Dominance All F1 are heterozygous X Figure 11.10 Page 184 F2 shows three phenotypes in 1:2:1 ratio Codominance: ABO Blood Types Gene that controls ABO type codes for enzyme that dictates structure of a glycolipid on blood cells Two alleles (IA and IB) are codominant when paired Third allele (i) is recessive to others ABO Blood Type: Allele Combinations Range of genotypes: Blood types: IA IA IB IB or or IA i IA IB IB i ii A AB B O Figure 11.11 Page 184 ABO and Transfusions Recipient’s immune system will attack blood cells that have an unfamiliar glycolipid on surface Type O is universal donor because it has neither type A nor type B glycolipid Pleiotropy Alleles at a single locus may have effects on two or more traits Marfan syndrome - Mutation in gene for fibrillin affects skeleton, cardiovascular system, lungs, eyes, and skin Epistasis Interaction between the products of gene pairs Common among genes for hair color in mammals Coat Color in Retrievers BBEE X bbee F1 puppies are all BbEe F2 puppies Figure 11.13 Page 186 BE Be bE be BE BBEE BBEe BbEE BbEe Be BBEe BBee BbEe Bbee bE BbEE BbEe bbEE bbEe be BbEe Bbee bbEe bbee black brown yellow Comb Shape in Poultry P: RRpp (rose comb) X rrPP (pea comb) F1: RrPp (all walnut comb) F2: 9/16 walnut RRPP RRPp RrPP RrPp 3/16 rose RRpp Rrpp 3/16 pea rrPP rrPp 1/16 single rrpp Figure 11.15 Page 187 Campodactyly: Unexpected Phenotypes Effect of allele varies: Bent fingers on both hands Bent fingers on one hand No effect Many factors affect gene expression Continuous Variation A more or less continuous range of small differences in a given trait among individuals The greater the number of genes and environmental factors that affect a trait, the more continuous the variation in versions of that trait Human Variation Some human traits occur as a few discrete types Attached or detached earlobes Many genetic disorders Other traits show continuous variation Height Weight Eye color (line of bell-shaped curve indicates continuous variation in population) Range of values for the trait Number of individuals with some value of the trait Number of individuals with some value of the trait Describing Continuous Variation Range of values for the trait Temperature Effects on Phenotype Rabbit is homozygous for an allele that specifies a heat-sensitive version of an enzyme in melaninproducing pathway Melanin is produced in cooler areas of body Figure 11.18 Page 190 Environmental Effects on Plant Phenotype Hydrangea macrophylla Action of gene responsible for floral color is influenced by soil acidity Flower color ranges from pink to blue