1. Heredity Heredity is the passing of traits from one generation to another, or inheritance.

2. Inherited Traits vs. Environmental Factors
Inherited Traits are those that are passed from parent to offspring
Environmental Factors can also have an effect on how you look
Diet
Exercise
Smoking/Drinking
Sun exposure

3. Why do I look like my parents
Why do I look like my parents?! You look like your parents because genetic information (DNA) is passed from parent to offspring during sexual reproduction. Each sex cell (egg or sperm) of the parent organism (plant or animal) contains one-half of the genetic material needed to create a new organism.

4. Who do you look like? Draw a picture of yourself and then label all of the traits that you inherited from someone in your family (write the family member’s name beside that trait) For example, if your hair is red and your mother’s hair is red, write her name beside your hair.

5. What are Chromosomes? A structure found in the nucleus of a cell that contains the genetic information (DNA). Remember, these are those things you were drawing that doubled and split in Mitosis and Meiosis. Humans have 46 in every cell except sex cells, which have 23.

7. What Is a Gene?
A gene is a segment of DNA found on a chromosome that determines the inheritance of a particular trait.
Genes are what make one individual look different from another

8. Principles of Heredity
Each trait is governed by two factors – now called genes.
2. Genes are found in alternative forms called alleles.
3. Some alleles are dominant and mask alleles that are recessive.

9. Dominant Traits Dominant Trait- a trait that will always be expressed in the phenotype. These alleles are represented by a capital letter. Ex. Having a widow’s peak is dominant to not having a widow’s peak.

11. Recessive Trait
Recessive Trait- a trait that will only be expressed in the phenotype if two recessive alleles are present. In the presence of a dominate trait, the recessive trait will not be expressed. These alleles are represented by lowercase letters.
Ex. Hitchhiker’s thumb is recessive to straight thumb.

12. Seven Traits used by Mendel in Genetic Studies

13. Genotype and Phenotype
Genotype: alleles carried by an individual ex. RR, Rr, rr
Phenotype: physical characteristic or appearance of an individual
ex. Round, wrinkled

14. Principles of Heredity
Mendel’s Experiment with Peas
Round seed x Wrinkled seed
RR rr
F1: All round seed coats Rr
Homozygous
Dominant
Homozygous
Recessive
Heterozygous

15. Homozygous parents can only pass one
form of an allele to their offspring. R

16. Heterozygous parents can pass either
of two forms of an allele to their offspring. R r R r

17. Principles of Heredity
Mendel was a scientist studying peas as a way to explore genetics.
He needed to explain:
Why one trait seemed to disappear in the first generation.
2. Why the same trait reappeared in the second generation in one-fourth of the offspring.

18. Mendel’s Principle of Genetic Segregation
In the formation of gametes, the members of a pair of alleles separate (or segregate) cleanly from each other so that only one member is included in each gamete.
Each gamete has an equal probability of containing either member of the allele pair.

19. Genetic Segregation Parentals: RR x rr F1 x F1: Rr x Rr R R r r

20. Genetic Segregation Genotypic Ratio: ¼ RR + ½ Rr + ¼ rr
Phenotypic Ratio: ¾ Round + ¼ Wrinkled

21. Mendel’s Principle of Independent Assortment
When gametes are formed, the alleles of one gene segregate independently of the alleles of another gene producing equal proportions of all possible gamete types.

22. Using Probability in Genetic Analysis
1. Probability (P) of an event (E) occurring:
P(E) = Number of ways that event E can occur
Total number of possible outcomes
Eg. P(Rr) from cross Rr x Rr ways to get Rr genotype possible outcomes P(Rr) = 2/4 = 1/2

23. Phenotypic Ratio of Offspring
Sex Determination
Female Male
XX x XY
½ X ½ X
½ X
½ Y
¼ XX
¼ XX
¼ XY
¼ XY
Phenotypic Ratio of Offspring
½ Female + ½ Male

25. Colorblindness

26. Pedigree for Colorblindness,
an X-linked Recessive Trait