Traits and Punnett Squares http://www.brainpop.com/science/cellularlifeandgenetics/heredity/zoom.weml https://www.youtube.com/watch?v=Mehz7tCxjSE&feature=youtu.be

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

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.

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

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

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

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

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

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

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

Punnett Square 2) Fill in parent genotypes B B b b 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 2) Fill in parent genotypes b b

Punnett Square 3) Complete offspring genotypes Bb Bb Bb Bb B B b b 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 3) Complete offspring genotypes Bb b Bb b Bb Bb

Punnett Square Determine % of genotypes of offspring: BB-0/4=0% 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

Punnett Square 5) Determine % of phenotypes of offspring: 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

Punnett Square Fill in parent genotypes 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. G g Fill in parent genotypes g g

Punnett Square Complete square gg Gg Gg gg 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. G g Complete square gg Gg g g Gg gg

Punnett Square gg Gg Gg gg 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. G g Genotypes: GG-0/4=0% Gg-2/4=50% gg-2/4=50% gg Gg g g Gg gg

Punnett Square Phenotypes: Green-2/4=50% Yellow-2/4=50% gg Gg Gg gg 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. G g Phenotypes: Green-2/4=50% Yellow-2/4=50% gg Gg g More practice: http://glencoe.mcgraw-hill.com/sites/0078778066/student_view0/chapter5/math_practice.html g Gg gg