Genetics
Travis Mackoy
Gregor Mendel
• 1860s
• Developed basic
principles of genetics
• Studied genetics of
pea plants
Basic Terminology
• Gene- Basic Unit of heredity
• Allele- Gene that exists in >1 form
• Genotype- Genetic makeup of individual
• Phenotype- Physical manifestation of
genotype
Mendel’s First Law:
Law of Segregation
• Genes exist in alternate forms
• Two alleles for each inherited trait; one from
each parent
• Alleles separate during meiosis, resulting in
gametes carrying one allele
• And…
Dominance
• If two alleles are different, one will be
dominant and the other will be silent.
• Dominant- denoted by capital letter
• Recessive- denoted by lower case letter
Punnett Square
• Way to predict monohybrid cross
• AA x aa
• A=black flowers, a=white flowers
Genotype: 1:3:1
Phenotype: 3 Black: 1 White
Mendel’s Second Law:
Law of Independent Assortment
• Dihybrid Cross
The Chromosomal Theory of
Inheritance
• Crossing Over/ Genetic Recombination
• Occurs during meiosis (Prophase I)
Variations on Mendelian
Genetics
• Incomplete
Dominance
• Co-dominance
• Sex Determination:
• Females have XX,
while males have XY