Unraveling Genetic Inheritance: How Our Traits Are Determined

1. The Genetics of Inheritance

2. Why do we look the way we do? • All organisms are made of cells. • Inside of these cells, a chemical called DNA contains the “instructions” that control the way we look. DNA

3. DNA: the instruction manual • The segments in the DNA that carry the “instructions” are called GENES. • Every individual has two of every gene. • There is more than one version of each gene. The different versions are called alleles. Brown Eyes Brown Hair Blue Eyes Fair Skin Black Hair Olive Skin

4. Dominant & Recessive Human Traits Earlobes: Widow’s peak: Free Attached One allele is dominant and the other allele is recessive. The dominant allele covers the expression of the recessive allele.

5. Genotype & Phenotype • The observable traits of an organism is called the phenotype. • The genotype is the combination of all of the different alleles that make up an individual

6. Incomplete Dominant Traits Blood types: Flower color: In incomplete dominance, the dominant allele does not cover up the expression of the recessive allele.

7. Why do we look like our parents? Aa aa Aa aa Aa Aa Aa Aa aa aa Aa aa

8. Punnett Squares • A diagram that is used to predict the genotype and phenotype of the offspring based on the genotype of the parents. pp It’s a probability problem! Pp ½ purple pea plants; ½ white pea plants

9. Punnett Squares • What is the probability that this couple will have a child with brown eyes? 2. What is the probability that this couple will have 3 children with brown eyes? Bb Bb Bb= BB= bb=

10. More Punnett Squares There are 10 guinea pigs in a litter. Five of the guinea pigs have long hair, and five have short hair. Long hair is dominant and short hair is recessive. What are the genotypes of the parents? Genotype for long hair: Genotype for short hair:

11. Applications of math in genetics Selective breeding—The selection of certain seeds or animals for reproduction so that the next generation has the same desirable traits.