1. Fundamentals of Genetics
Chapter 9

2. Trait Description Class numbers Tongue rolling Dimples Widow’s peak
Dimples  
Widow’s peak
Hitchhiker’s Thumb
Hand clasping, left over right thumb
Arm folding ­ fold your arms across your chest/stomach…which one is on top?
Free earlobe
Chin cleft
Hair on middle joints of fingers
Short big toe
Ear points
Round face
Curly hair
Blue Eyes
Brown Hair

5. Genetics is…..
The study of heredity, how characteristics are transmitted from parents to offspring.

7. Gregor Mendel “Father of Genetics”

8. Mendel studied garden peas and constructed the basis of genetics still used today.
He observed 7 traits in the plants (ex. plant height )
He noticed that traits in the offspring varied from the parent (ex. short plants came from tall plants).

9. 7 traits- pg 167 (DO NOT COPY)
Position of flower along stem
Height of plant
Pod appearance
Pod color
Seed texture
Seed color
Flower color

10. Mendel’s Experiments
Mendel grew pure plants for each of the 7 traits (pure meaning the offspring were just like the parent plants)
He called this the P1 generation
The pure plants were then cross-pollinated (tall plant crossed with a short plant)
These plants were the F1 generation

11. The F1 generation was allowed to self-pollinate
These plants were called the F2 generation

12. Test P1 generation – Tall plant x short plant
F1 generation – All tall plants (where are the short plants?)
F2 generation – Tall and short plants present

13. Mendel’s Conclusions
There are dominant and recessive traits. A dominant trait masks a recessive trait.
During the formation of sex cells, alleles are separated (one allele for a trait per sex cell)- Law of segregation
Alleles for different characteristics are distributed to sex cells independently – Law of independent assortment.

14. Genes
A gene is a segment of DNA on a chromosome that controls a particular trait (ex. height of a plant, eye color)
Genes occur in pairs, alleles make up the pair
Letters are used to represent alleles. Capital letter represents a dominant allele and a lower case represents a recessive allele.
T= tall plant; t = short plant

15. When both alleles of a pair are alike it is said to be homozygous (TT or tt)
When the alleles of a pair are different it is said to be heterozygous (Tt)

16. Genotype vs. Phenotype
Genotype – genetic makeup of an individual ; ex. Bb or TT
Phenotype – physical expression of the genotype; ex. brown eyes or tall plant

17. Punnett Square

18. A punnett square…..
A diagram used by biologists to aid them in predicting the probability that certain traits will be inherited by offspring
Types of crosses
Monohybrid – cross b/t one pair of traits Ex. Tt x TT
Dihybrid – cross b/t two pair of traits Ex. TtGG x TTgg

19. 3 possibilities….
Homozygous x Homozygous
Homozygous x Heterozygous
Heterozygous x Heterozygous

20. Do you know the genotype of a guinea pig just by looking at its appearance?
Black is the dominant coat color
BB or Bb would produce a black coat
To tell which, do a test cross and compare to offspring of the pig
Cross with a homozygous recessive

21. Incomplete Dominance
Two or more alleles influence the phenotype and cause a blending of traits.
Flower color, mouse coat, sickle cell anemia

22. Codominance (co= exist together)
Two or more alleles influence the phenotype and cause both phenotypes to appear.
Cattle coat color (spots) or Blood types (AB)
Do the Punnett square using different letters because neither traits are dominant

23. The “real” story behind eye color......
There are many genes involved and eye color can range from brown to hazel to green to blue to... How does eye color work? Eye color comes from a combination of black and yellow pigments called melanin in the iris of your eye. If you have no melanin in the front part of your iris, you have blue eyes. An increasing proportion of the yellow melanin, in combination with the black melanin, results in shades of colors between brown and blue, including green and hazel. What we are taught in high school biology is generally true, brown eye genes are dominant over green eye genes which are both dominant over blue eye genes. However, because many genes are required and certain combinations of pigments , there many possibilities in shades and color of ones eyes.