How is this possible?

Intro to Inheritance & Variation of Traits ___________________________

From Mom + Each person has 2 forms of a gene Allele: an alternative form of a gene that codes for the same trait – 1 from mom and 1 from dad – 2 alleles = 1 gene Forms of genes that code for same trait From Dad = Homologous Chromosomes

Phenotype : the observable characteristics or traits of an organism – Eye color: Blue or Brown Alleles both code for eye color Genotype : the combined alleles written in letters that code for a trait Exs: _____ _____

Some traits in humans exhibit a dominant/recessive pattern Dominant allele : An allele that masks other alleles. Only 1 dominant allele is needed to see the dominant phenotype. Represented by a capital-letter. – Brown eyes are dominant: _________ Recessive allele: An allele that can be overpowered by a dominant allele. Need 2 recessive alleles in order to see the recessive phenotype. The allele is represented by lower- cased letters: – Blue eyes are recessive: ________

Rules for writing genotypes: Dominant allele is always capitalized Recessive allele is always lower-cased Two alleles=one gene Homozygous = gene has two identical alleles – _______ or _______ Heterozygous = If the gene has different alleles For eyes color: – Brown eyes(dominant): ______ or _______ – Blue eyes(recessive): ______

Meiosis: When you make sex cells, you put only 1 allele into it. B b B b B b B b B b DNA Replication

Through sexual reproduction, each parent only gives 1 of their 2 alleles There are many possible outcomes, depending on what each parents’ genotypes are B b b B How to Predict Genotypes & Phenotypes

John is homozygous for brown eyes. Janie has blue eyes. What percent chance will their offspring have a blue eyes? ___ 2 possible alleles from one parent (2 gametes) 2 possible alleles for Other parent (2 gametes)

Dimples are a dominant Trait. Stephanie has dimples and is heterozygous. Tommy does not have dimples. Write the phenotypic and genotypic ratios of their genetic cross. ___

Working Backwards If you know the child’s phenotype, you can usually determine what genotypes the parents are: Cystic Fibrosis (F/f) is a recessive genetic disorder. Jackie has Cystic Fibrosis. Jackie’s mom also has Cystic Fibrosis. What must be her father’s genotype? ___

Tongue-Roller

Attached & Free Earlobes

Widow’s Peak

Regular vs. Hitchhiker’s Thumb

Bent Little Finger

Mid-digital hair

Dimples

Cleft Chin

Polydactyly

Regular vs. Morton’s Toe