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Notes: Genetics/Heredity

Copy all underlined for notes.

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Heredity

  • Heredity: The passing of traits from parents to offspring.
  • Trait: a distinguishing quality that can be traced through generations.
  • This means that you have a better chance of looking like your parents than anyone else.

Video: Patterns of Inheritance

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Common Human Traits

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Heredity

  • Genes: the part of the DNA that controls a certain trait or characteristic. Hair color, eye color, freckles, etc.

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Chromosomes

Humans have 23 pairs of chromosomes, half of each chromosome is inherited from the female parent and half from the male parent.

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Alleles

  • Alleles: The different forms of a gene.
  • TT, Tt, tT, tt.
  • These alleles usually come in opposites such as Tall or short, straight hair or curly hair, and freckles or no freckles.

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Alleles and Genes

Video

Genes

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Genotype

  • Genotype: the inherited combination of alleles in an organism, TT, Tt, tT, tt.
  • These are the actual genes in your DNA.

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Phenotype

  • Phenotype: the inherited appearance of an organism, tall or short.
  • This is what you look like or what you see.

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Genotype vs. Phenotype

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Homozygous

  • Homozygous/Purebred: When an organism has two of the same alleles for a trait, TT or tt.

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Heterozygous

  • Heterozygous/Hybrid: when an organism has different alleles for the same trait, Tt, tT.

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Donkey

Horse

Mule

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Dominant

  • Dominant Trait: A trait that always shows up in an organism when present, capital letter.

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Recessive

  • Recessive Trait: A trait that only shows up in an organism when the dominant trait is not present, lower-case letter.

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Round or Wrinkled

Green or Yellow

Purple or White

Smooth or Bumpy

Green or Yellow

Long or Short

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Dominant and Recessive

T=Tall

t=Short

H=no hair

h=hair

F=Fan

f=non fan

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Recessive

  • Recessive traits explain why it is possible for certain traits to skip generations.
  • Why may your grandmother have curly hair, your mother straight hair, and you curly hair?
  • Recessive traits can remain hidden.

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Punnett Square

  • Punnett Square: A chart that shows all of the possible combinations of alleles from a genetic cross.

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Video

Notes Heredity

Punnett Squares

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Punnett Square

Cross a homozygous tongue roller with a heterozygous tongue roller.

Dominant Allele=

Recessive Allele=

Genotype for homozygous tongue roller=

Genotype for heterozygous tongue roller=

Genotype outcomes=

Phenotype outcomes=

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Punnett Square

Cross a homozygous tongue roller with a homozygous non-tongue roller.

Dominant Allele=

Recessive Allele=

Genotype for homozygous tongue roller=

Genotype for homozygous non-tongue roller=

Genotype outcomes=

Phenotype outcomes=

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Punnett Square

Cross a heterozygous tongue roller with a heterozygous tongue roller.

Dominant Allele=

Recessive Allele=

Genotype for heterozygous tongue roller=

Genotype for heterozygous tongue roller=

Genotype outcomes=

Phenotype outcomes=

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Review

  • Video Mendel and Chromosomes