Download Heredity Inherited Traits

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)