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Dominant and Recessive Traits Cornell Notes: How are traits different? Are some traits more common than other traits? 1/23/14 & 1/27/14 Pd. 1 = pg. 77 Pd. 2 & 3 = pg. 73 Pd. 4 = pg. 61 What are traits? • Traits are characteristics • Physical Traits – Can be seen by others (they are observable) – Eye color, hair color, curly hair vs. straight hair, hairline, tongue roll, left handed vs. right handed • Acquired Traits – Learned skills – Playing a sport, riding a bike, playing a musical instrument • Behavioral Traits – Instincts (behaviors that do not need to be learned) – Nest building and migration in birds and some mammals – Behaviors can be learned Genetics Vocabulary • Genotype – The alleles (forms of genes) an individual has in its DNA (2 copies per trait – 1 copy from each parent) – Genes are inherited (passed down) from your biological parents – Genes control your traits • Phenotype – An individual’s observable traits (expression of the genotype) • What people can SEE when they look at you • Photograph = picture (what you see) like the Phenotype is the observable trait (what you see) Genetics Vocabulary • An individual with different alleles of a gene is heterozygous for that gene – Examples: Bb, Tt, Aa, (one dominant gene and one recessive gene) *Note: We use letters to represent the alleles or forms of a gene. Capital letter = dominant; Lower case letter = recessive • An individual with the same alleles of a gene is homozygous for that gene – Examples: BB or bb, TT or tt, (two dominant genes OR two recessive genes) Genetics Vocabulary • An allele is dominant if its effect hides the effect of a recessive allele paired with it • A recessive trait shows up in the phenotype ONLY if two recessive alleles are in the genotype – Capital letters (A) signify dominant alleles; lower case letters (a) signify recessive alleles – Homozygous dominant (AA) – Homozygous recessive (aa) – Heterozygous (Aa)