1. Today 1/25
Take a seat.

3. What is the difference between heredity & genetics?
The passing on of characteristics from parents to offspring is called heredity.
The study of heredity is genetics.

4. GREGOR MENDEL Austrian monk who worked in the monastery gardens.
One of the first to study heredity using pea plants from the gardens
“Father of genetics”

5. He studied 7 traits- one at a time.
seed seed seed pod pod flower plant
shape color coat shape color arrangmnt height

6. MENDEL’S EXPERIMENTS P-Generation- parent generation
Pollen from pure yellow seed plant crossed with egg of pure green seed plant
F1 Generation- first filial generation
First set of offspring from parent generation
All offspring were yellow.
Where did the green trait go?
Developed Rule of Dominance- one trait will overpower another even if both are present.
F2 Generation- second filial generation
Two offspring from first generation are mated
¾ of offspring were yellow, ¼ were green
How did the green trait reappear?
Developed two laws:
Law of Segregation
Law of Independent Assortment

7. MENDEL’S CONCLUSIONS Rule of Unit Factors
Inheritance is determined by genes passed from parent to offspring
The different forms a gene can take are called alleles.
You get one allele from mom & one allele from dad.
EX:
GENE- seed color
ALLELES- for seed
color are yellow
& green

8. MENDEL’S CONCLUSIONS
2. Rule of Dominance: Some alleles are dominant and others are recessive.
A. DOMINANT ALLELE
Gene that is shown
Represented by capital letter
EX: Yellow is dominant- Y
B. RECESSIVE ALLELE
Gene that is hidden when a dominant allele is present
Represented by a lowercase letter
EX: green is recessive- y

10. MENDEL’S CONCLUSIONS
Law of Segregation: Each pair of genes separates when gametes are formed during meiosis.
Explains the disappearance of a trait in the F1 generation and its reappearance in the F2 generation.

11. MENDEL’S CONCLUSIONS
4. Law of Independent Assortment- The genes for different traits are inherited independently of each other b/c there is no specific way the chromosomes must line up during metaphase of meiosis

12. PUNNETT SQUARES
Diagram that shows possible offspring that would result from two parents.
Shows probability that a allele will be passed to offspring TT
Tall Tt
Tall Tt
Tall tt
short

13. HOMOZYGOUS When two alleles in a pair are the same.
Also called purebred.
Can be either:
Homozygous dominant
Two dominant traits
YY- yellow
Homozygous recessive
Two recessive traits
yy- green

14. HETEROZYGOUS Have one dominant and one recessive allele.
Dominant allele is always expressed.
Person is a carrier for the recessive trait.
Also called hybrids
EX: Yy- looks yellow but carries a green trait

15. Compare phenotype and genotype
Genotype: gene combination of organism
ex: tt, TT, Tt, GG, gg
Phenotype: physical appearance of the organism
ex: short, tall, green, yellow

16. How do you set up a Punnett Square
READ the word problem.
Underline the parent’s phenotype.
Determine the parent’s genotype
Put one parent’s genotype on the top of the Punnett and other parent’s genotype down the left side.
Pull letters down into the boxes to show possible genotype combinations of offspring.
Determine the offspring phenotypes and write those in the boxes.
Determine genotype & phenotype percents/ratios for the offspring
Each box is worth 25% or ¼
Cross a homozygous dominant tall plant with a homozygous recessive short plant
Parent 1- TT
Parent 2- tt
Genotype Phenotype
TT- 0% Tall- 100%
Tt- 100% Short- 0%
Tt- 0%

17. Types of Punnett Squares
Monohybrid Crosses determining offspring’s chances of inheriting a single trait
Dihybrid Crosses- determining offsprings chances of inheriting two traits together.