1. Mendel performed cross-pollination in pea plants.
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
How Genetics Began
The passing of traits to the next generation is called inheritance, or heredity.
Mendel performed cross-pollination in pea plants.
Mendel followed various traits in the pea plants he bred.

2. How Genetics Began Mendelian Genetics Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
How Genetics Began

3. How Genetics Began Mendelian Genetics Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
How Genetics Began

4. The parent generation is also known as the P generation.
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
The parent generation is also known as the P generation.
The offspring of this P cross are called the first filial (F1) generation.
The second filial (F2) generation is the offspring from the F1 cross.

5. Section 2
Sexual Reproduction and Genetics

6. Section 2
Sexual Reproduction and Genetics
Mendelian Genetics

7. Dominant (Purple flower color)
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Genes in Pairs
Allele
An alternative form of a single gene passed from generation to generation
Dominant (Purple flower color)
Expressed form of a trait represented by a capital letter and first letter of the trait (P).
Recessive (White flower color)
Only appears when both alleles are recessive. Represented by a lower case letter of the dominant trait (p)

8. Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Dominance
An organism with two of the same alleles for a particular trait is homozygous.
PP or pp
An organism with two different alleles for a particular trait is heterozygous. Pp

9. Genotype and Phenotype
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Genotype and Phenotype
An organism’s allele pairs are called its genotype.
Example would be Pp
The observable characteristic or outward expression of an allele pair is called the phenotype.
Example would be purple flower color

10. Mendel’s Law of Segregation
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Mendel’s Law of Segregation
The law of segregation, states that the two alleles for a trait segregate (separate) when gametes are formed.
Two alleles for each trait separate during meiosis.
During fertilization, two alleles for that trait unite.
Each offspring receives one allele from each parent resulting in two alleles for each trait.

11. Mendel’s Law of Segregation
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Mendel’s Law of Segregation

12. Mendel’s Law of Independent Assortment
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Mendel’s Law of Independent Assortment
Mendel found that the inheritance of one trait, such as plant height, did not influence the inheritance of any other trait, such as flower color.
The law of independent assortment states that the alleles of different genes separate independently of one another during gamete formation.
This occurs during meiosis I when the homologous chromosomes line up along the metaphase plate

13. Mendel’s Law of Independent Assortment
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Mendel’s Law of Independent Assortment

14. Mendelian Genetics Mendel’s Laws Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Mendel’s Laws

15. Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Monohybrid Cross
A cross that involves hybrids for a single trait is called a monohybrid cross.

16. Predict the possible offspring of a cross between two known genotypes
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Punnett Squares
Predict the possible offspring of a cross between two known genotypes

17. Section 2
Sexual Reproduction and Genetics
Mendelian Genetics

18. Section 2
Sexual Reproduction and Genetics
Mendelian Genetics

19. Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Dihybrid Cross
The simultaneous inheritance of two or more traits in the same plant is a dihybrid cross.
For example, if you crossed a yellow round pea (YYRR) with a green wrinkled pea (yyrr)
What would be the predicted offspring genotypes and phenotypes?

20. Punnett Square—Dihybrid Cross
Section 2
Sexual Reproduction and Genetics
Mendelian Genetics
Punnett Square—Dihybrid Cross
Four types of alleles from the male gametes and four types of alleles from the female gametes can be produced.
The resulting phenotypic ratio is 9:3:3:1.

21. Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Incomplete Dominance
In some organisms, however, an individual displays a trait that is intermediate between the two parents, a condition known as incomplete dominance.
For example, when a snapdragon with red flowers is crossed with a snapdragon with white flowers, a snapdragon with pink flowers is produced.

22. Incomplete Dominance Complex Patterns of Inheritance Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Incomplete Dominance

23. Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Codominance
For some traits, two dominant alleles are expressed at the same time.
In this case, both forms of the trait are displayed, a phenomenon called codominance.
Codominance is different from incomplete dominance because both traits are displayed.
Instead of pink you would get a red and white flower
Comparing Dominances

24. Codominance Complex Patterns of Inheritance Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Codominance

25. Polygenic Inheritance
Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Polygenic Inheritance
When several genes influence a trait, the trait is said to be a polygenic trait.
The genes for a polygenic trait may be scattered along the same chromosome or located on different chromosomes.
Familiar examples of polygenic traits in humans include eye color, height, weight, and hair and skin color.

26. Polygenic Inheritance
Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Polygenic Inheritance

27. Genes with three or more alleles are said to have multiple alleles.
Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Multiple Alleles
Genes with three or more alleles are said to have multiple alleles.
Example: Blood types A, B, AB, and O
Multiple Alleles

28. Multiple Alleles Complex Patterns of Inheritance Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Multiple Alleles

29. Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Pedigree
Geneticists often prepare a pedigree, a family history that shows how a trait is inherited over several generations.
Pedigrees are particularly helpful if the trait is a genetic disorder and the family members want to know if they are carriers or if their children might get the disorder
Pedigree

30. Pedigree Complex Patterns of Inheritance Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Pedigree

31. Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Pedigree
Scientists can determine several pieces of genetic information from a pedigree:
Autosomal or Sex-Linked? If a trait is autosomal, it will appear in both sexes equally. If a trait is sex-linked, it is usually seen only in males. A sex-linked trait is a trait whose allele is located on the X chromosome.
Dominant or Recessive? If the trait is autosomal dominant, every individual with the trait will have a parent with the trait. If the trait is recessive, an individual with the trait can have one, two, or neither parent exhibit the trait.

32. Sex-linked - Hemophilia
Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Sex-linked - Hemophilia
Sex-linked traits occur on the X chromosomes
Females have 2 Xs so they must have both defective alleles to have the genetic disorder
Males only have 1 X making sex-linked disorders much more common in males
Sex-linked with Flies
Hemophilia is a sex-linked trait a condition that impairs the blood’s ability to clot.
Hemophilia

33. Sex-linked Complex Patterns of Inheritance Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Sex-linked

34. Sex-linked - Hemophilia
Section 3
Sexual Reproduction and Genetics
Complex Patterns of Inheritance
Sex-linked - Hemophilia