1 / 18

Understanding Traits, Alleles, and Punnett Squares in Genetics

This resource explores how traits are inherited through genetic alleles, providing insights into dominant and recessive alleles, including definitions of homozygous and heterozygous traits. It explains the structure of Punnett Squares and guides users through examples to predict offspring genotypes and phenotypes from parental trait combinations. By using Punnett Squares, you can visually determine the likelihood of various genetic traits appearing in future generations, helping to decipher the complex world of heredity and genetics.

feleti
Télécharger la présentation

Understanding Traits, Alleles, and Punnett Squares in Genetics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related