Slide 1 of 31 Copyright Pearson Prentice Hall 11-3 Exploring Mendelian Genetics 11–3 Exploring Mendelian Genetics

Slide 2 of 31 Copyright Pearson Prentice Hall The Law of Segregation It states that when an organism produces gametes its two alleles for a trait separate and go into different gametes. Therefore, when gametes from 2 parents join to produce a new organism, the offspring receive one allele from each parent.

11–3 Exploring Mendelian Genetics Slide 3 of 31 Copyright Pearson Prentice Hall

Slide 4 of 31 Does the gene for one trait have anything to do with whether the gene for another trait is inherited? Copyright Pearson Prentice Hall

Slide 5 of 31 Mendel showed that…. Different traits are inherited separately This is called the Law of Independent Assortment Copyright Pearson Prentice Hall

11–3 Exploring Mendelian Genetics Slide 6 of 31 Copyright Pearson Prentice Hall The alleles for rolling your tongue segregate independently of those for hair or eye color. This leads to genetic variation. Independent Assortment

11–3 Exploring Mendelian Genetics Slide 7 of 31 Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Some traits cannot be explained by simple dominant or recessive alleles. In fact, most genes have more than 2 alleles.

11–3 Exploring Mendelian Genetics Slide 8 of 31 Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Incomplete Dominance When one allele is not completely dominant over another it is called incomplete dominance. Blending!

Slide 9 of 31 11–3 Exploring Mendelian Genetics Copyright Pearson Prentice Hall A cross between red (RR) and white (WW) snapdragons produces pink- colored flowers (RW). Beyond Dominant and Recessive Alleles WW RR

11–3 Exploring Mendelian Genetics Slide 10 of 31 Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Codominance In codominance, both alleles contribute to the phenotype. In certain varieties of chicken, the allele for black feathers is codominant with the allele for white feathers. Heterozygous chickens are speckled with both black and white feathers. The black and white colors do not blend to form a new color, but appear separately and equally.

11–3 Exploring Mendelian Genetics Slide 11 of 31 Copyright Pearson Prentice Hall

11–3 Exploring Mendelian Genetics Slide 12 of 31 Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Multiple Alleles Each organism has only 2 alleles for a trait however, more than 2 alleles exist in a population. For example: a rabbit’s coat color. The coat color is determined by a single gene that has at least 4 different alleles.

11–3 Exploring Mendelian Genetics Slide 13 of 31 Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Different combinations of alleles result in the colors shown here. Full color: CC, Cc ch, Cc h, or Cc Chinchilla: c ch c h, c ch c ch, or c ch cHimalayan: c h c, or c h c h Full color: CC, Cc ch, Cc h, or Cc KEY C = full color; dominant to all other alleles c ch = chinchilla; partial defect in pigmentation; dominant to c h and c alleles c h = Himalayan; color in certain parts of the body; dominant to c allele c = albino; no color; recessive to all other alleles

11–3 Exploring Mendelian Genetics Slide 14 of 31 Copyright Pearson Prentice Hall Beyond Dominant and Recessive Alleles Polygenic Traits Traits controlled by two or more genes are said to be polygenic traits “having many genes.” Height in humans is a polygenic trait because it is controlled by multiple genes. Other examples include: eye color and skin color.

11–3 Exploring Mendelian Genetics Slide 15 of 31 Copyright Pearson Prentice Hall Pattern of InheritanceDescriptionExample Incomplete DominanceOne allele is not completely dominant over another Snapdragon plant: A plant with red flowers is crossed with a plant with white flowers, producing heterozygous plants with pink flowers. CodominanceBoth alleles contribute to the phenotype One variety of chicken: A black feathered chicken is crossed with a white feathered chicken, producing heterozygous speckled chickens. Multiple AllelesA gene has more than two alleles Rabbit fur color Polygenic TraitsTraits controlled by more than one gene Human skin color: Several genes control this trait, leading to a wide range of colors.

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