Applications of Mendel
Dominant/Recessive• For every gene/characteristic an
individual possesses two inherited copies (alleles)• One maternal, one paternal• EXAMPLE: Inherited attached earlobes
allele from mom, unattached earlobes allele from dad
• In cases of Mendellian inheritance, allele is dominant, one is recessive
Which is dominant?• EXAMPLE: Attached vs. Detached
earlobes• Possible gene combinations:• 2 attached genes (dd)• 1 attached, 1 detached (Dd)• 2 detached genes (DD)
Predicting inheritance…
• Punnett squares
Punnett Square
Dd Dd
Dd Dd
DD
d
d
Practice with Mendel1. Cross a pea plant with round peas (Rr)
with a pea plant with wrinkled peas(rr)
2. Cross a pea plant with green pods (Gg) with itself (Gg)
Genotype/Phenotype• Genotype: DD, Phenotype: Detached
earlobes• Genotype: dd, Phenotype: Attached
earlobes• Genotype: Dd, Phenotype: Detached
Earlobes
Genotype is actual gene combination
Phenotype is the observed trait
Genotype/Phenotype• Mary has the phenotype brown eyes
and curly hair. Can we know her genotype based on this information?
• Mary has the genotype Bb for eye color and CC for hair curl. B is for dominant brown, C is for dominant curly. Can we know her phenotype based on this information?
Homozygous/Heterozygous
• Homo=same• Hetero=different
• Heterozygous means two different alleles• Ex: earlobes (Dd)
• Homozygous means two of the same allele• Ex: earlobes (DD) or (dd)
• George has freckles. Can you tell if he is homozygous dominant or heterozygous dominant for this trait?
• George is heterozygous for freckles. Freckles are a dominant trait. Can you tell his phenotype given this information?
Wildtype/Mutant• Wildtype: most commonly occurring in
nature• Mutant: A deviation from the wildtype,
a less common allele