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Learning Targets “I Can...” Define “codominance.” Complete a Punnett Square for genes that are codominant. Define “incomplete dominance” and give an example. Complete a Punnett Square for genes that show incomplete dominance. Describe how the environment can affect the expression of genes. Define a “sex-linked gene.” Complete a Punnett Square for genes that are sex-linked.
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Special Inheritance Patterns
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Introduction 1. Determine if the following traits are dominant or recessive???
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Tongue Rolling
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Ear Lobe Attachment
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Widow’s Peak
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PTC Tasting
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Introduction 2. Many human traits are inherited in the typical dominant/recessive pattern.
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Unusual Inheritance Patterns 1. Incomplete dominance: the dominant allele does not completely dominate over the recessive allele (Incomplete and Codominant Traits worksheet #1 and 6) SNAPDRAGONS
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Unusual Inheritance Patterns RR ♂ x rr ♀ Red White Genotype frequency: Phenotype frequency:
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Unusual Inheritance Patterns 2. Codominance: two dominant alleles are equal in dominance
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Unusual Inheritance Patterns Example = Blood Types A and B are dominant; O is recessive Blood Type (Phenotype)Genotype A B O
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Unusual Inheritance Patterns Genotype frequency: Phenotype frequency:
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Unusual Inheritance Patterns 3. Polygenic Inheritance: many genes affect the same trait Example = skin color, eye color, hair color
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Gene Linkage (Fruit Fly Lab Data) 1. Review of Metaphase I during MeiosisMetaphase 2. The LAW OF INDEPENDENT ASSORTMENT states that chromosomes line up independently of one another
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Gene Linkage 3. Genetic variety of sex cells is increased
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Gene Linkage 4. Genes located on different chromosomes line up independently. But what about genes on the same chromosome?? 5. Linked genes: genes located on the SAME chromosome; these traits tend to be inherited together EXAMPLES: Blonde hair and blue eyes, Red hair and freckles
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Some dominant/recessive genes cause certain conditions (Human Genetic Disorder Worksheet #2 and 6) Examples 1. Dwarfism (dominant disorder) 2. Sickle Cell Anemia (recessive disorder)
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Other conditions are caused by sex- linked genes (Sex-linked Traits Worksheet #3, 7, and 8) Examples 1. Hemophilia 2. Colorblindness
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Other phenotypes are caused by sex- linked genes 3. Punnett squares for sex-linked traits: Hh, HH = normalhh = hemophilia X Y♂xX X ♀ Genotypic frequency: Phenotypic frequency:
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Other phenotypes are caused by sex- linked genes 3. Punnett squares for sex-linked traits: Hh, HH = normalhh = hemophilia X Y♂xX X ♀ Genotypic frequency: Phenotypic frequency:
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Other phenotypes are caused by sex- linked genes 4. Males are more likely to have sex-linked traits. Why? Males do not have an extra X chromosome to mask certain genes
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Some traits are sex-influenced. This means that the gene is expressed differently in males and females. 1. Genes are on autosomes 2. Genes must be activated by hormones
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References http://scienceprofonline.googlepages.com/Bentpinky.jpg/ Bentpinky-full.jpghttp://scienceprofonline.googlepages.com/Bentpinky.jpg/ Bentpinky-full.jpg http://www.scienceteacherprogram.org/images/Nakita08- 4.gifhttp://www.scienceteacherprogram.org/images/Nakita08- 4.gif http://www.ncrtec.org/tl/camp/gene/curl.jpg http://www.ncrtec.org/tl/camp/gene/widow.jpg http://learn.genetics.utah.edu/content/begin/traits/ptc/ima ges/DSC00100.jpghttp://learn.genetics.utah.edu/content/begin/traits/ptc/ima ges/DSC00100.jpg http://wiki.answers.com/Q/What_are_examples_of_domi nant_traitshttp://wiki.answers.com/Q/What_are_examples_of_domi nant_traits
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References http://porpax.bio.miami.edu/~cmallery/150/mendel/c14x9 incomplete-dominance.jpghttp://porpax.bio.miami.edu/~cmallery/150/mendel/c14x9 incomplete-dominance.jpg http://creationwiki.org/pool/images/thumb/c/c6/Codomina nt.jpg/200px-Codominant.jpghttp://creationwiki.org/pool/images/thumb/c/c6/Codomina nt.jpg/200px-Codominant.jpg http://www.gsboc.co.uk/graphics/pupscolour.jpg http://www.myherbalwellbeing.com/article_images/littleg uy.jpghttp://www.myherbalwellbeing.com/article_images/littleg uy.jpg http://scanned.files.wordpress.com/2007/12/ssa.jpg http://www.humanillnesses.com/original/images/hdc_000 1_0002_0_img0129.jpghttp://www.humanillnesses.com/original/images/hdc_000 1_0002_0_img0129.jpg http://comps.fotosearch.com/comp/BDX/BDX107/color- blindness-test_~bxp26007.jpghttp://comps.fotosearch.com/comp/BDX/BDX107/color- blindness-test_~bxp26007.jpg
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