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Learn about how traits are passed from parents to offspring, the concept of dominant and recessive traits, and the difference between phenotype and genotype. Discover the genetic makeup of traits such as hair color, freckles, widows peak, and tongue rolling. Practice determining phenotypes and genotypes for various traits.
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Genetic Traits Chapter 4: Heredity
After his experiments… Gregor Mendel calculated the ratios of dominant traits to recessive traits. (3:1)
What did this tell him about how traits are passed from parents to offspring? Mendel knew there must be two sets of instructions for each characteristic. Instructions = Genes He said… • Each parent gives one set of genes to the offspring. Gene—a heredity subunit of DNA Allele—different forms of a gene
What is a trait? Trait—a distinguishing characteristic of an organism
Dominant vs. Recessive Traits Dominant = Capital Letter (B) Recessive = Lowercase Letter (b)
Let’s Practice… What trait would be present? B= Brown hair b= Blonde hair Bb Brown
Let’s Practice… What trait would be present? F= Freckles f= No freckles FF Freckles
Let’s Practice… What trait would be present? W= Widows peak w= No widows peak Ww Widows peak
Let’s Practice… What trait would be present? T= Tongue rolling t= No tongue rolling tt No tongue rolling
Let’s Practice… What trait would be present? H= Curly hair h= Straight hair hh Straight hair
Genes affect the traits of offspring. Phenotype—appearance Ex: red hair, brown eyes Genotype—genetic makeup Ex: Bb, bb, BB Both inherited alleles together form an organism’s genotype. (one from the mother and one from the father)
What’s the phenotype? Genotype:Phenotype: BB Bb bb Brown Brown Blue Brown eyes = Dominant Blue eyes = Recessive
Homozygous vs. Heterozygous A genotype with two dominant or two recessive alleles is homozygous. A genotype that has one dominant and one recessive allele is heterozygous.
Heterozygous or Homozygous? AA Homozygous
Heterozygous or Homozygous? Bb Heterozygous
Heterozygous or Homozygous? Cc Heterozygous
Heterozygous or Homozygous? DD Homozygous
Heterozygous or Homozygous? Ee Heterozygous
Heterozygous or Homozygous? ff Homozygous
Determine the phenotype. Purple flowers are dominant to white flowers. PP Purple
Determine the phenotype. Purple flowers are dominant to white flowers. Pp Purple
Determine the phenotype. Purple flowers are dominant to white flowers. pp White
Determine the phenotype. Brown eyes are dominant to blue eyes. Bb Brown
Determine the phenotype. Brown eyes are dominant to blue eyes. BB Brown
Determine the phenotype. Brown eyes are dominant to blue eyes. bb Blue
Write the genotype. Curly hair is dominant to straight hair. Curly HH or Hh
Write the genotype. Curly hair is dominant to straight. Straight hair hh