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Traits and Inheritance or: Why am I, the I that I am?

Traits and Inheritance or: Why am I, the I that I am?. Genes. Gene – a set of instructions or an inherited trait Ex. Gene 1 for eye color Gene 2 for dimples, etc Each parent gives one set of genes to the offspring Allele – different forms of a gene

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Traits and Inheritance or: Why am I, the I that I am?

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  1. Traits and Inheritanceor: Why am I, the I that I am?

  2. Genes • Gene– a set of instructions or an inherited trait • Ex. Gene 1 for eye color Gene 2 for dimples, etc • Each parent gives one set of genes to the offspring • Allele– different forms of a gene • Ex. Gene 1 may be for brown or blue eyes • one is dominant (CAPITAL letter) • one is recessive (lowercase letter) Gene 1 Gene 2 chromosome

  3. Dominant and Recessive Dominant alleles are more common and show up more frequently than recessive alleles. • Which traits in pea plants did Mendel observe as dominant? • Purple flowers • Yellow seeds • Tall plants

  4. Allele • Gene 1 has instructions for eye color • The alleles are brown and blue Gene 1 - brown eyes Gene 1 – blue eyes Chromosome from mother Chromosome from father These two chromosomes make up a? Homologous pair

  5. Genotype • Both inherited alleles determine the genotype or an organism • Genotype is written, using the two alleles (letters) • If both inherited alleles are the same – homozygous • Both may be dominant (BB) • Both may be recessive (bb) • If one allele is dominant and one recessive – heterozygous (Bb)

  6. The appearance of an organism • Mendel observed that pea • plant flowers could be purple • or white. Phenotype • Their phenotype was either purple or white. • What is your phenotype for eye color?

  7. Example: Guinea Pigs! Guinea pigs have alleles which contain genes for fur color. Imagine a baby guinea which had the following alleles: • The allele from mom is for Brown fur (B) • The allele from dad is for White fur (b) Which Allele is Dominant? __________ What is the genotype? _____________ What is the phenotype? ____________ brown Bb brown

  8. How is this useful? Selective breeding • Breed animals for the traits we want them to have • The genotypes of the parents can help us predict the phenotypes of the offspring • We can use the genotype to find the probability of each phenotype non-shedding dogs • fat chickens

  9. Homozygous or Heterozygous Red (R) is dominant for red flowers, and white (r) flowers are recessive. How would you write: • Homozygous dominant ____ • Homozygous recessive ______ • Heterozygous ______ RR rr Rr

  10. Illustrates how the parent’s alleles might combine in offspring Top of the square shows one parent’s alleles for the trait Punnett Squares Side of the square shows second parent’s alleles for the trait Each box shows how the alleles might combine in potential offspring

  11. Punnett Squares • What is the chance of a blue eyed parent (bb) and a brown eyed parent (BB) producing brown eyed offspring? b b Genotype: Bb B B b B b Phenotype: Brown eyes (100%) Blue eyes (0 %) B B b B b

  12. Punnett Squares • What are the chances of a blue eyed parent (bb) and a heterozygous Brown eyed parent (Bb) producing blue eyed offspring? b b Genotype: Bb bb B B b B b Phenotype: Brown eyes (50%) Blue eyes (50%) b b b b b

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