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Dominant and Recessive. Dominant – the trait we see (expressed with capital letter, A) Recessive – trait that is masked (expressed with lower case letter, a) Which is better, dominant or recessive?. Dominance. Organism with two of the same allele – homozygous AA, aa
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Dominant and Recessive • Dominant – the trait we see (expressed with capital letter, A) • Recessive – trait that is masked (expressed with lower case letter, a) • Which is better, dominant or recessive?
Dominance • Organism with two of the same allele – homozygous • AA, aa • Organism with two different alleles – heterozygous • Aa • Dominant trait observed (notice the dominant allele)
Homozygous (pure bred) Same HH hh
Heterozygous (hybrid) Different Hh Rr
Genotype Allele makeup of an individual Tt T T tt RR Rr rr
Phenotype Observable characteristics of an individual
Predicting traits • Punnett Squares
Practice A Tt (tall) plant is crossed with a tt (short plant). What percentage of the offspring will be tall?
A green pea sead (gg) is crossed with a hybrid yellow seed (Gg). What will be the genotypic and phenotypic ratios of the offspring?
A heterozygous plant (Tt) is crossed with another heterozygous (Tt) plant. What percentage of the offspring will be tall?
In guinea pigs, rough coats are dominant over smooth coats. An Rr guinea pig is crossed with an Rr guinea pig. What are the chances of each genotype and phenotype? Include genotypic and phenotypic ratios.
Dihybrid Cross • a cross between two individuals looking at two different traits For example: GGbb/ggBb or RRYY/rryy