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Genetics Notes
What is heredity?
A. Traits passing from offspring to parents
B. Traits passing from parents to offspring
C. Plants that are cross-pollinatedD. The ratio of dominant to recessive
traits
Heredity is
“C” - The passing of traits from parent to offspring
Who was Gregor Mendel?
Austrian Monk Conducted his research in a
monastery garden Worked with pea plants Discovered the principles of heredity
Self-pollinating Peas
Self-pollinating – when a plant fertilizes itself Results in a true-bred plant All the offspring of a true-bred plant will have
the same trait as the parent
Parent
Offspring
Cross-pollinating Peas
When one plant fertilizes a different plant
Pollen from one plant lands on the pistil and fertilizes the ovule (egg) of a different flower on a different plant
• Wind• Bees & other insects
First Generation Plants
First Generation Plants Self -Pollinated
X
F2 Second Generation
The white flowers reappeared! How did this happen?
Alleles: *different forms of a gene *exist in pairs (one from mom & one from dad)
Dominant allele– the prevailing (stronger) traitCapital Letter
Recessive allele– the (weak) hidden traitLower case letter
Genotype – the combination of alleles you have for a specific trait
• Ex: RR or Rr or rr
Phenotype – the physical feature you show or see
• Ex: Red flower petals, white flower petals
Example:
Gene: Flower Petal Color Alleles:
• Red (R)• White (r)
RR = homozygous dominantrr = homozygous recessiveRr = heterozygous
Homo – the same Hetero - different
Complete Dominance Rr = Red• dominant trait shows
Co Dominance RW = Red & White• Both traits show
Incomplete Dominance Rr = Pink• Traits are blended (mixed)
First Generation Plants Self -Pollinated
X
F2 Second Generation
The white flowers reappeared! HOW?
The parents were heterozygous (Rr).
RrRr
RRRr
Rr rr
Mendel’s Discoveries:
Each trait has two sets of instructions (alleles), one from each parent
Discovered dominant and recessive traits.
Intro. to Punnett Squares
A chart used to show all the ways genes from two parents can combine and be passed to offspring.