1. Mendel and Mendelian Genetics

2. I. Gregor Mendel
Heredity – passing of characteristics (traits) from parents to offspring
Genetics – biology that studies heredity

3. II. Pea Plant Experiments
Breeding pea plants
Reproduce sexually
Fertilization – gametes form zygote (fertilized cell)
Pollination – pollen grains from male to female

4. II. Pea Plant Experiments
Cross pollination – breed one plant with another (did it manually)

5. II. Pea Plant Experiments
Mendel observed seven characteristics.
Each occurred in two contrasting traits.

6. II. Pea Plant Experiments (Monohybrid Cross)
Mendel crossed short
plant with tall plant
(P Generation).
ALL offspring (hybrids)
were tall. (F1 Generation)
2nd Generation (F2) – tall plants from 1st generation to self-pollinate

8. III. Mendel’s Conclusions
Each organism has two factors that control each trait
Alleles – genes in alternative form
Genes – parts of chromosomes (DNA) that control specific characteristics

9. III. Mendel’s Conclusions
Organisms ALWAYS have two alleles (one on each chromosome)
Alleles can be either dominant or recessive

10. III. Mendel’s Conclusions
Dominant trait – masks the presence of other traits for the same characteristic
Recessive trait – is masked by dominant trait for the same characteristic

11. IV. Rule of Dominance
If an organism had one dominant allele, this trait would be expressed, hiding the recessive trait
Capital letters = Dominant allele
Lowercase = Recessive

12. V. Law of Segregation
There are alternate versions of genes called alleles.
For each characteristic, an organism inherits two alleles.
Alleles interact in a number of ways.
The two alleles for a trait separate during gamete production

13. Vocabulary
Phenotype – observed characteristics (example: long or short neck)
Genotype – genetic makeup of an individual (example: Nn or nn)

14. Vocabulary Homozygous – two of the same alleles
Homozygous dominant - two dominant alleles (TT)
Homozygous recessive – two recessive alleles (tt)

15. Vocabulary Heterozygous – two different alleles (Tt)
One is dominant and one is recessive

16. Example Long necks in giraffes are dominant to short necks (N and n)
Genes vs. displayed trait

17. VII. Law of Independent Assortment
Inheritance of one trait will not affect the inheritance of another.
Only true for traits not linked.

18. VIII. Punnett Squares Reginald Punnet (1905) developed Punnet squares.
Monohybrid Cross

19. VIII. Punnett Squares
Shows probability, yet not exact outcomes (genetics follows rule of chance)