1. Fundamentals of Genetics
Chapter 6
Fundamentals of Genetics

2. What will we study? 6.1 Patterns of Inheritance
6.2 Principles of Inheritance
6.3 Genetics and Predictions
6.4 Difficult Predictions

3. 6.1 Patterns of Inheritance
You should be able to:
Distinguish between dominant and recessive traits
Analyze the results Mendel’s experiments with three generations of garden peas

4. History of Genetics 1st experimentation with genetics was with dogs
Dogs were dangerous wild animals
Now, they are domesticated

5. Because dogs are descended from wolves, many of the behaviors and abilities of the wolf are present in the genetic make-up of the domesticated dog (Weston-Ross,1992). What humans have done through selective breeding, particularly in the last 100 years, is to modify the wolf into a variety of breeds shapes and sizes.

7. Genetics The study of heredity Chromosomes, genes, DNA
The transmission of traits

8. Trait
A structure, function, or attribute that makes an individual unique
Determined by a genes

9. Mitosis/Meiosis
Interphase
Chromosomes replicate

10. Gregor Mendel Born: 22 July 1822
Birthplace: Hyncice, Moravia (now Czech Republic)
Died: 6 January 1884
Best Known As: The founding father of modern genetics

11. Mendel’s Experiments
Studied the traits of ~20,000 pea plants for 8 years
Collect data about each plant’s specific traits
Applied mathematics (Punnett squares and probability)
Result: explained Inheritance

13. Pea Plant

14. Pea Plant Fertilization
One plant is both male and female
Male: pollen (sperm) produced by anther
Female: egg produced in pistil

15. Self-fertilization
The pollen from the anther falls into the pistil of the same flower
The plant gets the same genetic traits from both of parents
Forms purebred offspring

16. Cross-pollination
The pollen from one anther falls into the pistil of a different flower
2 different parents
Form hybrid offspring

17. Offspring Purebred Called pedigreed
breeding individuals of unmixed lineage over many generations
Parents have same traits
Hybrid
Genetically dissimilar parents
offspring produced by breeding plants or animals of different varieties, species, or races.

18. Garden Pea Plants Traits exist in 2 forms, easy to observe
Reproduce in 90 days (fast)
Get results quickly and easily repeatable

20. Mendel’s Generations P = parents
F1 = first filial, first generation of pea plant offspring
F2 = second filial, second generation of pea plant offspring

23. Blending Hypothesis Mendel expected two different traits would blend
Ex. Green + yellow = chartreuse offspring
NOT VALID!!!

24. Results of Experiments
When he crossed Green + Yellow
All offspring were yellow
What happened to the green????

25. Trial 1
In cross-pollinating plants that either produce yellow or green peas exclusively
Mendel found that the first offspring generation (f1) always has yellow peas.  
However, the following generation (f2) consistently has a 3:1 ratio of yellow to green.

26. Trial 2

27. Mendel’s Conclusions
The inheritance of each trait is determined by Genes ("units" or "factors“) that are passed on to descendents unchanged     
An individual inherits a gene from each parent for each trait
A trait may not show up in an individual but can still be passed on to the next generation.

29. Terms you must know
Gene
Allele
Dominant allele
Recessive allele

30. Genes Made up of DNA Found in the cell nucleus
Carries instructions for the development of an organism and all its traits

31. Allele Any of a number of alternative forms of a gene.
A dominant allele will override the traits of a recessive allele in a heterozygous pairing
Example
In the case of the gene for eye color
One allele codes for blue eyes, one for brown eyes, one for green eyes

32. Traits
Many traits are determined by pairs of complementary genes ( 2 genes)
Each inherited from a single parent.
Often these 2 genes are paired and compared

33. Dominant allele
This allele will turn off the instructions from the recessive gene.

34. Recessive allele A gene only expressed in the homozygous state
When paired with a dominant allele its expression is masked