1. BELL RINGER
If a green pea pod plant is crossed with a yellow pea pod plant, what will the offspring look like? X
ALL the offspring will be green!

2. Father of Genetics
GENETICS: study of heredity
HEREDITY: passing of traits from parent to offspring
TRAITS: characteristics
Learned about these patterns by studying PEAS

3. How do traits get passed from parent to offspring?
Through GAMETES: sex cells
Male gamete is the SPERM
Female gamete is the EGG
FERTILIZATION: union of egg & sperm
ZYGOTE: fertilized egg

4. GENES VS. ALLELES Each form of a gene is called an ALLELE EXAMPLE:
Segment of DNA that codes for one protein/trait
Most traits are determined by TWO genes.
Remember chromsomes have a homologous match…two chromosomes with similar genetic information
EXAMPLE:
hair color
eye color
height in pea plants
Each form of a gene is called an ALLELE
EXAMPLE:
brown or blond
blue, hazel, brown
tall, short

5. Law of Dominance DOMINANT (allele) Always expressed if present
Only need ONE dominant allele to be expressed
EXAMPLES:
dark hair, brown eyes,
tall peas
RECESSIVE (allele)
May be present but will not be expressed if paired w/ dominant allele
Requires TWO recessive alleles for recessive trait to be expressed
EXAMPLES:
light hair, blue eyes, short peas

6. Law of Segregation
Gene pairs separate during formation of gametes (meiosis)
Each gamete gets ONE allele from a pair
Each parent passes down one allele to their offspring (
Offspring get 2 alleles (one from each parent)

7. Preparing for Genetic Crosses
Letters will represent alleles
Use the first letter of the dominant trait
Capital letter = dominant trait
Lower case letter = recessive trait
EXAMPLE: height in pea plants
TALL is dominant over short, so…
T = tall t = short

8. All possible combinations using T, t: TT, tt, Tt, tT
Genotype vs. Phenotype
All possible combinations using T, t: TT, tt, Tt, tT
GENOTYPE: actual genes in the pair; can’t see…they’re on chromosomes…but they determine the individual’s traits
Use terms:
homozygous: both genes the same (TT, tt)
heterozygous:genes different; 1 dominant, 1 recessive (Tt, tT)
PHENOTYPE: the trait that is expressed; the ‘physical’ appearance
P G
TT…tall (homoz dom)
tt….short (homoz rec)
Tt….tall (heterozygous)
tT….tall (heterozygous

10. Mendelalian Traits Traits that have 2 alleles EXAMPLE: cleft chin
If a person inherits two dominant alleles (CC) or one dominant & one recessive (Cc), they will have a cleft chin (top)
If a person inherits 2 recessive alleles (cc), they will not have a cleft chin (bottom)

11. Solving Genetic Crosses
Use PUNNETT SQUARES
Shows POSSIBLE GENOTYPES of offspring
The parents gametes go on outside of square (one parents’ gametes across top; other parents’ gametes down left side
Remember: each gamete has only ONE allele