Introduction to Heredity

1. Introduction to Heredity

2. What is Heredity? • Heredity is the passing of traits from parents to offspring • Genetics is the study of heredity

3. Gregor Mendel • Known as the “Father of Genetics” • Austrian Monk • Born in 1822

4. Mendel’s Work • Experimented with “True Breeding” pea plants in his garden • True Breeding • Plants that produce identical offspring when allowed to self pollinate • AKA “Purebred” • Discovered how traits are passed from parent to offspring in sexual reproduction

5. What is a Trait? • A trait is a notable feature or quality in a person • http://learn.genetics.utah.edu/content/begin/traits/tour_trait.html

6. TraitsInherited vs. Acquired Some traits can be both! Skin Color Received genes for skin color from both parents Amount of time in the sun affects skin color

7. Genes • A gene is a unit of heredity • Occupies a specific location on a chromosome • Codes for or determines a specific trait • Most traits are not coded for by just one gene

8. Genes and Chromosomes • Genes are located on chromosomes • Chromosomes come in pairs • Each pair is called a homolog • On each homolog are sites where specific genes are located

10. Alleles • Alleles are various forms of the same gene. • Example 1: • Gene: Eye Color • Alleles: Brown, Blue, Hazel • Example 2: • Gene: Seed Color • Alleles: Green, white, yellow

11. Mendel’s Work, continued • Mendel also performed experiments with hybrid plants • Hybrids - Plants that were produced by parents with different traits • In these experiments, he discovered that traits are inherited by parents passing allelesto their offspring

12. Mendel’s Conclusions(Principles of Heredity) • Individuals carry twoalleles for each trait, but only pass down one to their offspring • One allele is dominant over another

13. Alleles determine traits • An organism’s traits are controlled by the alleles it inherits from its parents • Mendel discovered that there are two types of alleles: • Dominant • Recessive

14. Dominant Alleles • Dominant Allele: an allele whose trait is always shows up in the organism when the allele is present • Expressed if only one is present • Example: Brown Eye Color

15. Recessive Alleles • Recessive Allele: an allele whose trait is hidden whenever the dominant one is present • Can only be expressed if two are present • Example: Blue Eye Color

18. Alleles are represented by symbols w W

19. Alleles interact to produce traits W • Each parent contributes ONE allele for a given trait • The combination of alleles from parents can result in varying traits in their offspring Alleles for widows peak chromosomes w

20. Genetic Terminology • Genotype: An organisms genetic makeup, or alleles an organism has for a trait is its genotype • Ww, Bb, bb, ww, etc • Phenotype: An organism’s physical appearance, or visible traits is its phenotype. • Widow’s peak, brown eyes, blue eyes, straight hairline, etc

22. Example: Flower Color

23. Genetic Terminology • Terms used to describe an organisms genotype • Heterozygous – an organism that has two different alleles for a trait is said to be heterozygous • Example: Ww, Bb • Homozygous – An organism that has two identical alleles for a trait is said to be homozygous • Example: WW, ww, BB, bb

24. Using Genetic Terminology Homozygous Recessive Homozygous Dominant Heterozygous

25. Using Genetic Terminology Homozygous Recessive Homozygous Dominant Heterozygous

26. Using Genetic Terminology Homozygous Recessive Homozygous Dominant Heterozygous

27. Using Genetic Terminology Homozygous Recessive Homozygous Dominant Heterozygous

28. Using Genetic Terminology Homozygous Recessive Homozygous Dominant Heterozygous

29. Can you determine an organism’s genotype just by looking at it?

30. Traits in a population • Observable characteristics we inherit from our parents • Some traits are common in a population, while others are not • Every person has a different overall combination of traits that make them unique