Download Chapter 5 Section 1

Chapter 5 Section 1
Mendel’s Work
Gregor Mendel
• A priest in Europe during the 1800’s that worked
in a monastery garden and taught high school.
– Considered the “Father of Genetics”
– Most famous for growing and studying pea plants and
heredity
• Heredity is the passing of physical traits from
parents to offspring
– Physical traits are characteristics you can see
• Genetics is the study of heredity
Mendel’s Experiments
• Crossing (Mating) Pea Plants
– Mendel first created purebred pea plants
• A purebred organism always produces offspring with the same
trait as the parent (tall plant produces more tall plants)
• These were the parent (P) plants
– Mendel crossed tall purebred pea plants with short
purebred plants
• The offspring (F1 generation) were all (100%) tall
– Mendel crossed the F1 generation plants
• The offspring (F2 generation) were 75% tall 25% short
Dominant and Recessive Alleles
• Mendel concluded that there were “factors” that
control traits
– These factors are now called genes
• Alleles are different forms of a gene
• There are two alleles for each trait. One from each parent.
– A dominant allele always shows up
• Shown by a upper case letter (T = allele for tall pea plant)
• TT (purebred) and Tt (hybrid) will result in a tall plant
– A recessive allele is hidden when a dominant is present
• Shown with a lower case letter (t = allele for short pea plant)
• Recessive traits only show up if there are two recessive alleles.
• tt (purebred) will result in a short pea plant