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Explore the fascinating world of genetics and heredity, understanding how traits are passed from parents to offspring. Learn about alleles, dominant and recessive genes, and how our genetic makeup influences physical appearance and behavior. Discover why a child can have different eye color than their parents despite genetic inheritance.
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Question… A child is born with blue eyes even though BOTH his parents have brown eyes. How is this possible? Can two blue eyed parents have a brown eyed child? Explain why or why not.
Genetics: The study of heredity
Heredity = the passing of traits from parents to offspring • Trait = A feature or characteristic of a person • Physical appearance • Behavior tendencies • Predisposed to medical conditions • A person’s traits are influenced by: • their genetic inheritance • environmental factors What is a trait?
Trait = a feature or characteristic of a person • Physical appearance • Genetics: • Environment: hair color eye color face shape hair texture smile shape
Trait = a feature or characteristic of a person • Physical appearance • Genetics: genes determine natural hair color • Environment: hair color eye color face shape hair texture smile shape
Trait = a feature or characteristic of a person • Physical appearance • Genetics: genes determine natural hair color • Environment:sun or hair dyes change hair color hair color eye color face shape hair texture smile shape
Trait = a feature or characteristic of a person • Behavior tendencies • Genetics: • Environment:
Trait = a feature or characteristic of a person • Behavior tendencies • Genetics: genes determine the tendency to use a certain hand • Environment:
Trait = a feature or characteristic of a person • Behavior tendencies • Genetics: genes determine the tendency to use a certain hand • Environment: can learn to use the opposite hand
Trait = a feature or characteristic of a person • Predisposed to medical conditions • Genetics: • Environment:
Trait = a feature or characteristic of a person • Predisposed to medical conditions • Genetics: genes determine a risk of heart disease • Environment:
Trait = a feature or characteristic of a person • Predisposed to medical conditions • Genetics: genes determine a risk of heart disease • Environment: eating healthy foods and exercising can reduce risk
Trait = a feature or characteristic of a person • Phenotype = a person’s version of a trait • “physical appearance” hair color: black eye color: blue hair texture: straight
Practice • List 3 traits Dash has. • List Dash’s phenotype for each trait.
Trait = a feature or characteristic of a person • Gene = part of a person’s DNA that influences a trait Eye color gene Face shape gene Hair color gene
Gene= part of a person’s DNA that controls a trait • Alleles= different versions of a gene Eye color gene: brown allele Eye color gene: blue allele
Practice • List 3 possible alleles for the hair color gene. Hair color gene
Alleles = different versions of a gene • Dominant Allele • Represented by a capital letter • Example: B for brown eyes • Recessive allele • Represented by a lowercase letter • Example:b for blue eyes
Alleles = different versions of a gene • All people have 2 alleles for every gene (one from each parent) Allele of eye color gene from dad Allele of eye color gene from mom
Alleles = different versions of a gene • All people have 2 alleles for every gene (one from each parent) • Genotype = a person’s combination of alleles • “genetic makeup” Allele of eye color gene from dad Allele of eye color gene from mom
Genotype = a person’s combination of alleles • A person may inherit 2 of the same alleles = purebred or Homozygous • 2 dominant alleles = purebred/Homozygous dominant • Example: B and B Genotype = Phenotype = Mom Dad E E Child
Genotype = a person’s combination of alleles • A person may inherit 2 of the same alleles = purebred or Homozygous • 2 dominant alleles = purebred/Homozygousdominant • Example: B and B Genotype = BB Phenotype = Mom Dad E E Child
Genotype = a person’s combination of alleles • A person may inherit 2 of the same alleles = purebred or homozygous • 2 dominant alleles = purebred/homozygous dominant • Example: B and B Genotype = BB Phenotype = brown eyes Mom Dad E E Child
Genotype = a person’s combination of alleles • A person may inherit 2 of the same alleles = purebred • 2 recessive alleles = Mom Dad e e Child
Genotype = a person’s combination of alleles • A person may inherit 2 of the same alleles = purebred • 2 recessive alleles = purebred recessive • Example: b and b Genotype = Phenotype = Mom Dad e e Child
Genotype = a person’s combination of alleles • A person may inherit 2 of the same alleles = purebred or homozygous • 2 recessive alleles = purebred/homozygous recessive • Example: b and b Genotype = bb Phenotype = Mom Dad e e Child
Genotype = a person’s combination of alleles • A person may inherit 2 of the same alleles = purebred or homozygous • 2 recessive alleles = purebred/homozygous recessive • Example: b and b Genotype = bb Phenotype = blue eyes Mom Dad e e Child
Alleles = different versions of a gene • A person may inherit 2 different alleles = hybrid or heterozygous • Dominant allele masks recessive allele • Example: B and b Genotype = Phenotype = Mom Dad Mom Dad e E E e -or- Child Child
Alleles = different versions of a gene • A person may inherit 2 different alleles = hybrid or heterozygous • Dominant allele masks recessive allele • Example: B and b Genotype = Bb Phenotype = Mom Dad Mom Dad e E E e -or- Child Child
Alleles = different versions of a gene • A person may inherit 2 different alleles = hybrid or heterozygous • Dominant allele masks recessive allele • Example: B and b Genotype = Bb Phenotype = brown eyes Mom Dad Mom Dad e E E e -or- Child Child
Practice • Brown hair (B) is dominant to blond hair (b).
Practice • Brown hair (B) is dominant to blond hair (b).
Practice • Brown hair (B) is dominant to blonde hair (b).
Practice • Brown hair (B) is dominant to blond hair (b). Which genotypes are purebred? Which ishybrid?
Practice • Right-handedness (R) is dominant to left-handedness (r). What genotype(s) could a right-handed person have? What genotype(s) could a left-handed person have? RR or Rr rr
Practice • In pea plants, green peas (G) are dominant to yellow peas (g). What would be the genotype of a: -purebred green pea? -hybrid green pea? -yellow pea? GG Gg gg