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Traits and Punnett Squares

Traits and Punnett Squares. http://www.brainpop.com/science/cellularlifeandgenetics/heredity/zoom.weml. Traits and Alleles. Traits are characteristics passed from your parents, ex) eye color Each cell in your body has a complete set of DNA-46 chromosomes (23 from mom, 23 from dad)

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Traits and Punnett Squares

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  1. Traits and Punnett Squares http://www.brainpop.com/science/cellularlifeandgenetics/heredity/zoom.weml

  2. Traits and Alleles • Traits are characteristics passed from your parents, ex) eye color • Each cell in your body has a complete set of DNA-46 chromosomes (23 from mom, 23 from dad) • Sex cells (sperm and egg) have 23 chromosomes each • Each trait is determined by a pair of genes, called alleles • For each trait, you have 1 allele from mom, 1 allele from dad. • Alleles are shown by using letters, ex) T for height • Alleles are considered dominant or recessive

  3. Dominant Alleles • An allele that masks a recessive alleles • Dominant alleles are shown in capital letters. • Presence of the dominant allele will mean the dominant trait is shown ex) Tt or TT • Dominant alleles are always listed first-so it would be Tt not tT.

  4. Recessive Alleles • An allele that is masked by a dominant allele • Recessive alleles are shown in lower case letters. • The only way that a recessive trait is shown is if there are 2 of them-1 from each parent Ex) tt

  5. Homozygous Traits or Alleles • Means that there are 2 of the same alleles ex) TT or tt • Pure is another word for homozygous

  6. Heterozygous Traits or Alleles • Means that there are 2 different alleles ex) Tt • Hybrid is another term for heterozygous

  7. Genotype • What 2 alleles are present Ex) TT or Tt or tt

  8. Phenotype • What trait is shown-the characteristic that is shown Ex) tall or short

  9. Punnett Square • Used to determine the genotype and phenotype of offspring Steps: • Draw square • Fill in parent genotypes • Complete offspring genotypes • Determine % of genotypes of offspring • Determine % of phenotypes of offspring

  10. Punnett Square Example Steps: • Draw square Example 1) A brown (BB) rabbit is crossed with a white rabbit (bb). For their offspring, give the % of each genotype and each phenotype.

  11. Punnett Square Example 1)A brown (BB) rabbit is crossed with a white rabbit (bb). For their offspring, give the % of each genotype and each phenotype. 2) Fill in parent genotypes B B b b

  12. Punnett Square Example 1)A brown (BB) rabbit is crossed with a white rabbit (bb). For their offspring, give the % of each genotype and each phenotype. 3) Complete offspring genotypes B B Bb b Bb b Bb Bb

  13. Punnett Square Example 1)A brown (BB) rabbit is crossed with a white rabbit (bb). For their offspring, give the % of each genotype and each phenotype. B B • Determine % of genotypes of offspring: • BB-0/4=0% • Bb-4/4=100% • bb-0/4=0% Bb b Bb b Bb Bb

  14. Punnett Square Example 1)A brown (BB) rabbit is crossed with a white rabbit (bb). For their offspring, give the % of each genotype and each phenotype. B B 5) Determine % of phenotypes of offspring: Brown-4/4=100% White-0/4=0 % Bb b Bb b Bb Bb

  15. Punnett Square Example 2) A cross is done between green (Gg) and yellow parent plants (gg). For their offspring, give the % of each genotype and each phenotype. Fill in parent genotypes g G g g

  16. Punnett Square Example 2) A cross is done between green (Gg) and yellow parent plants (gg). For their offspring, give the % of each genotype and each phenotype. Complete square g G gg Gg g g Gg gg

  17. Punnett Square Example 2) A cross is done between green (Gg) and yellow parent plants (gg). For their offspring, give the % of each genotype and each phenotype. Genotypes: GG-0/4=0% Gg-2/4=50% gg-2/4=50% g G gg Gg g g Gg gg

  18. Punnett Square Example 2) A cross is done between green (Gg) and yellow parent plants (gg). For their offspring, give the % of each genotype and each phenotype. Phenotypes: Green-2/4=50% Yellow-2/4=50% g G gg Gg g More practice: http://glencoe.mcgraw-hill.com/sites/0078778066/student_view0/chapter5/math_practice.html g Gg gg

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