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Inheritance

Inheritance. What is the genotype and the phenotype of an individual? Predict the probabilities for the offspring of any cross. Complete dominance, codominance , incomplete dominance, sex-linked, polygenic, multiple alleles

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Inheritance

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  1. Inheritance • What is the genotype and the phenotype of an individual? • Predict the probabilities for the offspring of any cross. • Complete dominance, codominance, incomplete dominance, sex-linked, polygenic, multiple alleles • Describe Tay-Sachs disease, CF, Huntington disease, sickle-cell disease, and PKU. • What do you think about genetic profiling?

  2. Genetics “lingo” Chromosome---DNA---Gene Genotype • Alleles • Dominant allele • Recessive allele • Homozygous dominant genotype • Homozygous recessive genotype • Heterozygous genotype

  3. Phenotype Phenotype – the physical or outward expression of the genotype GenotypePhenotype EE unattached earlobe Ee unattached earlobe ee attached earlobe What are your genotype and phenotype?

  4. Crosses • Monohybrid cross • If an individual has the genotype Ff what are the possible gametes that this individual can pass on?

  5. Punnett squares • What is the genotypic ratio? • What is the phenotypic ratio?

  6. Practicing a punnett square for a 2-trait cross • What would the punnett square look like for a dihybrid cross between a male that is WWSS and a female that is wwss? • F1 cross? • Try some practice problems… • Are you ready for a shortcut?

  7. Is there a way to tell which chromosome a gene is located on? • Autosomal? Or • X-linked? Y-linked?

  8. Autosomal recessive disorder • Individuals must be homozygous recessive to have the disorder • Parents are usually carriers (Aa)

  9. Autosomal dominant disorder • Individuals that are homozygous dominant and heterozygous will have the disorder • Disorder doesn’t usually skip a generation

  10. Genetic disorders of interest • Tay-Sachs disease: lack of the enzyme that breaks down lipids in __________resulting in excess and eventually death of a baby • Cystic fibrosis: _________do not pass normally through a cell membrane resulting in thick mucus in lungs and digestive tract • Phenylketonuria (PKU): lack of an enzyme needed to use __________________and affects nervous system development • Sickle-Cell disease: ___________________are sickle shaped rather than biconcave that clog blood vessels • Huntington disease: huntingtin protein has too many glutamine amino acids leading to the progressive degeneration of ________________

  11. Genetic disorders

  12. X-linked disorders • More often found in males than females because recessive alleles are always expressed • Most X-linked disorders are recessive: • Color blindness: • SCID: “Bubble Boy” disease • Muscular dystrophy: characterized by wasting of muscles and death by age ____ • Hemophilia: characterized by the absence of particular _____________ factors Calico cats: Why didn’t CC look like Rainbow?

  13. X-linked inheritance: Color blindness Cross: XBXb x XBY Possible offspring: XBXB normal vision female XBXb normal vision female XBY normal vision male XbY normal vision male

  14. X-linked disorders • More males than females have the trait • Males inherit the trait from their mothers

  15. X-linked disorders: Hemophilia

  16. Polygenic inheritance • Polygenic traits - two or more sets of genes govern one trait • Each dominant allele codes for a product so these effects are additive • Results in a continuous variation of phenotypes • e.g. skin color, height, blood pressure, metabolism… • Multifactorial trait – a polygenic trait that is particularly influenced by the environment • Can you think of any diseases that are polygenic and multifactorial?

  17. Incomplete dominance • Occurs when the heterozygote is intermediate between the 2 homozygotes • Example: (curly hair) CC x C’C’ (straight hair) CC’ What will the phenotype be?

  18. Codominance • Occurs when the alleles are equally expressed in a heterozygote • Example: (red) RR x R’R’ (white) RR’ What will the phenotype be?

  19. Multiple allele inheritance • ABO blood system • A and B are codominant alleles • The O allele is recessive to both A and B therefore to have this blood type you must have 2 recessive alleles

  20. Multiple allele inheritance Based on what you know what type of blood would each of the following individuals have in a cross between A and B? possible genotypes:phenotypes: IAIB Type AB blood IBIB , IBi Type B blood IAIA, IAi Type A blood ii Type O blood

  21. Blood type inheritance

  22. Bioethical focus: Genetic profiling • What benefits and risks would come from knowing the genetic disorders that you may develop in the future? • Insurance companies, employers, health care, biochips…

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