1. Gregor Mendel

2. Genetics
Field of Biology that studies how characteristics are transferred from parent to offspring
Begins, chronologically, with the work of Austrian monk Gregor Johann Mendel in the s.

3. Mendel: Early Life
Born in 1822 to a farming family in the Austrian Empire
Often portrayed as a lucky, observant monk

4. Mendel: Early Life Entered monastery in Brno, Austria at age 21
Gardener

5. Mendel: Education In fact, Mendel was a well-educated scientist
Studied physics and mathematics at the Olmütz Philosophical Institute at the University of Vienna, beginning in 1851

6. Mendel: Education
Monastery had over twenty-thousand books

7. Mendel: Experiments
Famous experiments involving breeding pea plants

8. Mendel: Experiments Painstakingly careful:
Two years PREPARING
Two full-time assistants
Thirty thousand plants
Perfect notes (slightest variations)
In short, “Mendel knew what he was doing.”

9. Mendel: Legacy Often called “Father of Genetics”
NEVER used the word “gene”
Found two factors within each seed that could be used to predict patterns in inheritance in offspring

10. Mendel: Legacy Experiments took 8 years
Presented to an uninterested audience of 40 in 1865

11. Mendel’s Experiments

12. Pea Plants Mendel observed seven characteristics.
Each occurred in two contrasting traits.

13. Characteristics Plant height (short or tall)
Flower position (axial or terminal)
Pea pod color (green or yellow)
Pea pod appearance (inflated or constricted)
Seed texture (smooth or wrinkled)
Seed color (yellow or green)
Flower color (purple or white)

14. Pea Plant Experiments Experiment 1: Plant Height
Mendel crossed a short
plant with a tall plant.
All offspring were tall.
Crossing two of the offspring resulted in 787 tall plants and 277 short plants – HOW???

15. Pea Plant Experiments Experiment 2: Seed Color
Mendel crossed a yellow-seed plant with a green-seed plant.
All offspring had yellow seeds.
Crossing two of the offspring resulted in 6,022 yellow-seed plants and 2001 green-seed plants – HOW???

16. Vocabulary Parents called P Generation Offspring called F1 Generation
Offspring’s offspring called F2 Generation

17. Mendel’s Conclusions
Some FACTOR within the pea plants controlled what trait appeared in the offspring
Because the traits he studied had two alternate forms, he hypothesized that each plant had a PAIR of factors

18. Mendelian Genetics

19. Mendel’s Results
One P generation trait always failed to appear in the F1 generation, but reappeared in F2 generation
One trait must hide, or “dominate” the other (i.e. trait for yellow seeds dominates trait for green seeds)

20. Vocabulary
Dominant trait – masks the presence of other traits for the same characteristic
Recessive trait – is masked by dominant trait for the same characteristc

21. Vocabulary
Genes – parts of chromosomes (DNA) that control specific characteristics

22. Molecular Genetics
How many of each type of chromosome does a cell have?
TWO! (Chromosomes
come in pairs.)

23. Vocabulary
Alleles – several alternate forms of a gene that cause different traits
Example: one allele may cause blonde hair, while another causes black

24. Alleles Organisms ALWAYS have two alleles (one on each chromosome)
Alleles can be either dominant or recessive

25. Alleles Letters are used to represent alleles
Capital letters = dominant genes
Lowercase letters = recessive genes

26. Alleles Example: short hair is dominant over hairless in dogs
Short hair: H
Hairless: h

27. Alleles
Since organisms have two of each type of chromosome (with one allele on each), genes must be represented by two letters
Examples: HH, Hh, or hh

28. Alleles Dominant alleles mask recessive HH – 2 dom.
Hh – 1 dom., 1 rec.
hh – 2 rec.

29. Alleles Dominant alleles mask recessive HH – dominant trait
Short hair
Hh – dominant trait
Short Hair
hh – recessive trait
Hairless

30. Vocabulary Homozygous – two of the same alleles
Homozygous dominant - two dominant alleles
Homozygous recessive – two recessive alleles

31. Vocabulary Heterozygous – two different alleles
Usually one is dominant and one is recessive

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

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