5&6.Inheritance

5&6.Inheritance - Roles of mitosis and meiosis in...

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Unformatted text preview: Roles of mitosis and meiosis in various life cycles Many simple eukaryotes remain haploid In sexual life cycle, meiosis occurs before gametes form Plants, some algae, and some fungi have complex life cycles with alternation of generations If a diploid cell replicates its DNA so that it now contains 4n, how does a haploid gamete get a 1n number of chromosomes and a 1n amount of DNA? er e Th Th Th Th er e 25% 25% 25% 1. There are two meiotic divisions and four daughter cells produced in meiotic cell division. 2. There is only one meiotic division and two daughter cells produced in meiotic cell division. 3. There is only one meiotic division and four daughter cells produced in meiotic cell division. 4. There are two meiotic divisions and two daughter cells produced in meiotic cell division. m ei ot i.. m e. ... .. . e on o on e m ei ly tw ly on on e ar is er e er e ar is e tw o 25% m ei ot ic ... Inheritance and Genetics Basic Patterns of Inheritance characteristics from parents are transferred to offspring inherited characteristic is not "blended" dominant recessive Mendel's Laws of Inheritance (mid 1800's) 1. Equal Segregation "2 copies of a gene separate during meiosis into different gametes" P = purple (dominant) p = white (recessive) Punnett square Mendel's Laws of Inheritance 2. Independent Assortment "genes are segregated and inherited independently of other genes" Color and texture R = round r = wrinkled Y = yellow y = green Exceptions to Mendel's Laws 1. Incomplete Dominance/ Codominance 1. Modifier Genes/ Polygenic Inheritance 1. Environmental Influences Exceptions to Mendel's Laws 1. Incomplete dominance: Heterozygotes phenotype is intermediate Codominance: Heterozygotes express both alleles Chestnut (CC) Palomino (Cc) Cremello (cc) Incomplete dominance in four o'clocks Exceptions to Mendel's Laws 1. many phenotypes depend upon multiple genes Black (BB, Bb) Brown (bb) White (cc + BB, Bb or bb) Multiple alleles in rabbits Polygenic Trait Eye color is determined by the amount of melanin Heterochromia iridium Heterochromia iridium results from alteration to one of the genes. inherited trait, trauma, medications Gene interaction Epistasis in Labrador retrievers Exceptions to Mendel's Laws 1. environment can have an effect on genes temperature dark = low light = high typically colder Norm of reaction Range of phenotypic possibilities from a single genotype under different environmental conditions Example height Polygenic inheritance in human skin pigmentation Human Genetics Human Genetics 23 pairs of chromosomes 1739 genes/chromosome 8,388,608 genes Human Genetics 23 pairs of chromosomes 1739 genes/chromosome 8,388,608 genes 40,000 80,000 genes Gender male = XY Female = XX Inherited Genetic Diseases Inherited Recessive Genetic Diseases Heterozygote Advantage Sex-Linked inherited Genetic Diseases X-linked Y-linked X-linked red-green colorblindness Genetically Inherited Human Diseases Autosomal Recessive Disorders Symptoms show in homozygous recessive Autosomal Dominant Disorders Symptoms show with just 1 allele Autosomal Recessive Cystic Fibrosis cc Tay-Sachs tt Sickle Cell ss Pedigree Analysis cystic fibrosis (recessive genetic disease) Aa Aa Aa Aa Aa Aa AA aa aa Aa Aa Aa Heterozygote Advantage???? Hh + h Hh hh Hh H Homozygous Dominant H h HH Hh Homozygous Recessive Autosomal Dominant Achondroplasia AA is lethal!!! Aa = dwarfism aa = no dwarfism Polydactyly AA or Aa = extra digits Progeria Premature aging Huntington's chorea Hh Marfan's syndrome Pedigree Analysis congenital generalized hypertrichosis (CGH) dominant or recessive? X-linked? CGH Pedigree (Aa) AA AA AA dominant or recessive? Punnett Square (recessive) a a A Aa Aa A Aa Aa recessive in F1? CGH Pedigree (Aa) AA AA AA dominant or recessive? CGH Pedigree (Aa) XaY XAXa XaY XaXa X-linked? Punnett Square (X-linked) X A X A a XX a Y A XY XY a X a XX a a who is affected? CGH Pedigree (Aa) XaY XAXa XaXa XaY XAXa XAY XaXa X-linked? CGH Pedigree (Aa) XaY XAXa XaXa XaY XAXa XAY XaXa X-linked most likely. ...
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