Today’s Agenda 2-6 Bellringer: What is a trait? Get your clickers! Notes on Genetics Homework: Worksheet

Genetics Part I Study Pack #8

Today’s Goal… I can explain how traits are inherited.

Let’s see what you know… True or False All traits are inherited An allele is one form of a gene If an allele is recessive the trait will always show up If an organism is homozygous for a trait it has two alleles that are different

Traits Characteristics of an organism Learned traits are a result of experiences and the environment Examples: learning how to play an instrument or not touching a hot stove Inherited traits are passed from parent to offspring in reproduction Examples: infants have 10 fingers and 10 toes and breath as soon as they are born

Heredity Heredity is the passing of traits from parent to offspring Genetics is the study of heredity An organism is a collection of traits inherited from its parents Traits are passed on through genes on chromosomes

Allele An allele is one form of a gene You have two for every trait During meiosis alleles separate into different sex cells

Allele During fertilization, each parent donates one chromosome from each pair This results in two alleles for each trait Page 307

Dominant and Recessive Alleles The trait you end up with depends on your combination of alleles and which are dominant and recessive

Dominant and Recessive Alleles A dominant allele is one whose trait always shows up in the organism when the allele is present

Dominant and Recessive Alleles A recessive allele is covered up, whenever the dominant allele is present Will only show up if the organism does not have the dominant allele

Dominant and Recessive Alleles Dominant alleles are written with a capital letter Recessive alleles are written with a lower case letter

Homozygous and Heterozygous Traits An organism with two alleles that are the same is homozygous Two dominant alleles Two recessive alleles An organism that has two different alleles is heterozygous

Let’s see what you know… True or False All traits are inherited An allele is one form of a gene If an allele is recessive the trait will always show up If an organism is homozygous for a trait it has two alleles that are different