Notes: Genetics and Heredity

1. Notes: Genetics and Heredity • Sci.7.10A & Sci.7.10C

2. What is Heredity? • Heredity is the passing along of traits from parent to offspring or children. • Traits are the physical characteristics that an organism contains. Example-hair color, eye color, hair texture • Genetics is the study of heredity

3. Inherited Traits vs. Learned Traits • Inherited traits are physical characteristics that organisms inherit from their parents. They are passed down from parents to offspring through reproduction. • Learned traits are characteristics that are learned or influenced by their environment. They are behaviors.

4. Which of the following characteristics are inherited? Which of the following characteristics are learned? • Having naturally curly hair • Obesity • Having a good singing voice • Having brown eyes • Being intelligent • Having attached ear lobes

5. What are some traits that this family share?

6. DNA • Traits are found on DNA which stands for deoxyribonucleic acid. • The DNA in every cell is located in rod like structures called chromosomes within the nucleus of cells.

7. How would you describe the shape of DNA?

8. Alleles • Genes come in two different called alleles. • A dominant allele is one whose traits are always physically expressed in the organism when the allele is present. • A recessive allele is a masked or covered up whenever the dominant allele is present. A recessive trait will only appear when both alleles are recessive.

9. Dominant/Recessive Alleles • Remember alleles are two different forms of a trait. • Ex: Height is a trait. Tall is the dominant allele-written as a “T”. Short is the recessive allele-written as a “t”. • Dominant alleles are always written as capital letters. • Recessive alleles are always written as lower-case letters.

10. Phenotype vs. Genotype • Phenotype is the physical appearance • Ex: Hair color (blonde, brown, red or black) and Eye color (blue, brown, green, grey) • Genotype is its genetic makeup or combination of alleles. BB, Bb, bb

11. Which trait is dominant? Which trait is recessive? How can you tell by looking at genotype?

12. What is the trait being examined in the diagram?

13. Which trait is controlled by the dominant allele? Which trait is controlled by the recessive allele?

14. What is the phenotype being examined in the diagram?

15. Identify the dominant phenotype. Identify the recessive phenotpye. How do you know?

16. Homozygous and heterozygous • An organism that has two identical alleles for a trait is said to be homozygous. • Ex: A tall plant that has the alleles TT and a short plant with the alleles tt are both homozygous. • An organism that has two different alleles for a trait is said to be heterozygous. • Ex: A tall plant that has the alleles Tt is heterozygous.

17. Describing Genotype-Homozygous dominant, homozygous recessive and heterozygous • A homozygous dominant genotype is a combination of alleles where both alleles are dominant. • Ex: TT for tall plants • A homozygous recessive genotype is a combination of alleles where both alleles are recessive. • Ex: tt for short plant • Heterozygous is a combination of both dominant and recessive alleles. The dominant allele is always written first followed by the recessive allele. • Ex: Tt for tall plants

18. What is Carrie’s genotype? What is Rusty’s genotype?

19. What percentage of the offspring are heterozygous for tall?