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Introduction to Genetics

Introduction to Genetics. Chapter 11. The Work of Gregor Mendel. Genetics. The scientific study of heredity. Vocabulary to Know. Trait : a specific characteristic varying among individuals ex: eye color Gene : a portion of DNA determining a trait; found on the chromosomes

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Introduction to Genetics

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  1. Introduction to Genetics Chapter 11

  2. The Work of Gregor Mendel

  3. Genetics • The scientific study of heredity.

  4. Vocabulary to Know • Trait: a specific characteristic varying among individuals ex: eye color • Gene: a portion of DNA determining a trait; found on the chromosomes ex: the gene for eye color

  5. Vocabulary (continued) • Hybrid: the offspring of two parents with different traits • Gametes: reproductive cells (aka: sex cells; sperm & egg)

  6. Allele: the form of a gene • Allele: the different forms of a gene * Represented by a letter. ex: Widow’s Peak = W * Organisms have two alleles for each trait, one inherited from the mother and one from the father. ex: WW

  7. Forms of Alleles Dominant Allele: trait will be expressed with only one copy present * Represented with capital letters. ex: W (Widow’s peak) Recessive Allele: trait will only be expressed when no dominant alleles are present * Represented with lower case letters. ex: w (No widow’s peak)

  8. Gregor Mendel • Considered the father of genetics. • Mid-1800s • Monk who experimented with pea plants in the monastery garden.

  9. Mendel’s Conclusions • Inheritanceis determined by factors passed from one generation to the next. 2. Principle of dominance: Some alleles are dominant and others are recessive.

  10. Mendel’s Conclusions 3. Segregation: A gamete carries only one copy of each gene. 4. Principle of independent assortment: Genes for different traits segregate independently from one another.

  11. Applying Mendel’s Principles

  12. Allele Combinations • Homozygous: both alleles are the same ex: WW or ww • Heterozygous: alleles are different ex: Ww (capital letter is always 1st!)

  13. Genotype: the actual allele combination; what the genes say ex: WW, Ww, ww • Phenotype: the trait observed ex: Widow’s Peak

  14. Punnett Squares • Used to predict the genotypes of offspring when the genotypes of both parents is known.

  15. Other Patterns of Inheritance

  16. Incomplete Dominance The heterozygous phenotype (Ww) is somewhere between both homozygous phenotypes (WW & ww). Ex: pink flowers

  17. Codominance Both alleles contribute to the phenotype; neither allele is dominant . Ex: roan cattle

  18. Multiple Alleles • More than two allele possibilities. • Ex: blood type

  19. Polygenic Traits • Traits controlled by more than one gene. • Ex: skin color

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