Genetics
the scientific study of heredity
How do we get our traits? Why are we tall,
short, blonde? What makes us; us?
Hitchhiker’s Thumb
Slater with his dimples
Human Traits & Genetics
• Every living thing – plant or animal, microbe or
human being – has a set of characteristics
inherited from its parent or parents.
• How do genes work? What are they made of,
and how do they determine the characteristics
of organisms?
Gregor Mendel
• Gregor Mendel “Father of Genetics” (1864)
- Austrian Monk, studied Heredity
He preformed experiments with these pea
plants by forcing plants with different traits to
pollinate each other.
Parents – first generation
pollinated
F1 – first offspring
F2 – Second offspring
Traits
• Alleles – Gene form, Y or y, for each
variation of a trait of an organism.
• Dominant – visible, observable trait
of an organism that masks a
recessive form of a trait.
• Recessive – A hidden trait of an
organism that is masked by a
dominant trait.
Genotype and Phenotype
• Genotype – the gene combination
of an organism.
• Phenotype – the way an organism
looks and behaves. Physical
characteristics of an organism.
Gregor Mendel
• Mendel observed seven traits that are easily
recognized and apparently only occur in one of two
forms:
1. flower color is purple or white
2. seed color is yellow or green
3. flower position is axil or terminal
4. pod shape is inflated or constricted
5. stem length is long or short
6. pod color is yellow or green
7. seed shape is round or wrinkled
Law of Segregation
After noticing that the allele for green seeds
reappeared in the second generation,
Mendel concluded that the two alleles for
each trait must separate when gametes are
formed.
• Law of Segregation – In other words, A
parent only passes one form of a gene or
allele (i.e. either A or a but not both) at
random to each offspring.