1. Fundamentals of Genetics
Ch.9

2. (9-1) Genetics
Field of Bio focused on how characteristics are passed from parent to offspring (heredity)
Gregor Mendel
“Father of Genetics”

3. Mendel’s Peas Studied 7 characteristics (heritable features) of peas
Ex: plant height
Each characteristic had 2
different traits
Ex: long or short stems

4. Mendel’s Experiments
Started w/ 2 pure plant groups for a particular characteristic
P generation
Cross-pollinated (sexual reprod.) those plants to produce the next generation
F1 generation

6. Experiments (cont.)
Allowed F1 plants to self-pollinate (asexual) to produce the next generation
F2 generation

7. Mendel’s Results F1 always showed only 1 of the 2 traits
Dominant factor: masked other trait
F2 always showed a 3:1 ratio b/w the 2 traits
Recessive factor: factor being masked

8. Mendel’s Laws
Segregation
Independent Assortment

9. Law of Segregation
A pair of factors separate during gamete (sex cell) formation

10. Law of Independent Assortment
Factors for different characteristics are distributed to gametes independently
Ex: not all blue eyed people have blond hair

11. Molecular Genetics
Study of the structure & function of chromo.’s & genes
Allele: alternate form of a gene
Dominant = capital letter (B)
Recessive = lower case letter (b)

13. (9-2) Genetic Crosses Genotype: genetic makeup
BB, Bb, bb
Phenotype: physical appearance
Not all alleles shown
BB = black, Bb = black, bb = white

15. Genotype Vocab
Homozygous (purebred): same alleles for the characteristic
BB = ho/go dominant
bb = ho/go recessive
Heterozygous (Hybrid): different alleles for the characteristic Bb

16. Probability Likelihood that a specific event will occur
Determined by a Punnett square

17. Punnett Squares Monohybrid Cross – 1 characteristic
Dihybrid Cross – 2 “
Trihybrid Cross – 3 “

19. Testcross Dominant phenotype, but what genotype?
Unknown genotype crossed w/ ho/go recessive

21. Complications Incomplete dominance Codominance Multiple alleles
Pleiotropy
Polygenic Inheritance
Epistasis

22. Incomplete Dominance Both alleles blend to make phenotype Ex:
red (RR) x white (rr)
= pink (Rr)

23. Codominance Both alleles expressed in a he/go offspring No blending!
Ex: red (RR) x white (rr) = roan (Rr)
Roan = red & white

24. Multiple-alleles
Traits controlled by 3 or more alleles of the same gene
Blood groups (A, B, O)

25. Pleiotropy
1 gene affects many characters
Hemoglobin sickling allele

27. Polygenic Traits
1 trait determined by multiple genes
Skin color

28. Epistasis Expression of 1 gene depends on another Hair color &
albinism genes