6.5 Traits and Probability

Quick Review Gene – a piece of DNA that provides a set of instructions. Trait - distinguishing characteristics that are inherited Alleles – any of the alternative forms of a gene that occurs at a specific locus on a chromosome. Each gene has two alleles! Homozygous – two of the same alleles at a specific locus Heterozygous – two different alleles at a specific locus Law of segregation – Mendel’s First Law Organisms inherit two copies of each gene, one from each parent. Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate during gamete formation.

Yy Quick Review Genotype Phenotype Genotype – the genetic makeup of a specific set of genes Phenotype – the physical characteristics, or traits Genotype Phenotype Yy

Quick Review Dominate allele – the allele that is expressed when two different alleles or two dominate alleles are present Recessive allele - the allele that is only expressed when two copies are present Ted Ed - Mendel

Mendel’s Laws Law of segregation – Mendel’s First Law Organisms inherit two copies of each gene, one from each parent. Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate during gamete formation. Law of independent assortment – Mendel’s Second Law Allele pairs separate independently of each other during gamete formation (meiosis). Different traits seem to be inherited separately.

Punnett Squares Punnett square – a grid system for predicting all possible genotypes resulting from a cross Only show probability! http://xkcdsw.com/2394

? Punnett Squares What hair color could their child possibly have? Remember: The allele for brown hair is dominate.

? BB? Bb? BB? Bb? Punnett Squares What hair color could the child possibly have? BB? Bb? ? BB? Bb?

? Punnett Squares What hair color could the child possibly have? Let’s look at the possibilities. BB x BB BB x Bb Bb x Bb ?

B B B B Punnett Squares BB x BB BB x Bb Bb x Bb Homozygous - Homozygous BB x BB BB x Bb Bb x Bb B B

Punnett Squares B B BB x BB B B B B B B

Punnett Squares B B BB x BB BB BB B B BB BB

B B BB BB B B BB BB Punnett Squares BB x BB Genotype: 4 BB; 0 Bb; 0 bb Phenotype: 4 brown hair 100% chance of brown hair offspring BB BB B B BB BB

b B B b Punnett Squares BB x BB BB x Bb Bb x Bb Heterozygous - Heterozygous BB x BB BB x Bb Bb x Bb B b

Punnett Squares b B B B b b B b

Punnett Squares b B B BB Bb b Bb bb

b B B BB Bb b Bb bb Punnett Squares Genotype: 1 BB; 2 Bb; 1 bb Phenotype: 3 brown hair; 1 blond hair 3:1 75% - brown 25% - blonde B BB Bb b Bb bb

B B B b Punnett Squares BB x BB BB x Bb Bb x Bb Homozygous - Heterozygous BB x BB BB x Bb Bb x Bb B b

Punnett Squares B B BB x Bb B B B b B B

Punnett Squares B B BB x Bb BB BB B b Bb Bb

B B BB BB B b Bb Bb Punnett Squares BB x Bb Genotype: 2 BB; 2 Bb; 0 bb Phenotype: 4 brown hair 1:1 100% - brown 50% homozygous 50% heterozygous BB BB B b Bb Bb

Punnett Squares BB BB BB Bb ? BB Bb Bb Bb bb

Heterozygous – Heterozygous Punnett Squares Bb Bb bb Bb x Bb Heterozygous – Heterozygous 25% chance of blonde hair They had a blonde hair baby!

Crosses B B Monohybrid cross – examine the inheritance of only one specific trait homozygous – homozygous heterozygous – heterozygous heterozygous– homozygous BB BB B b Bb Bb

Crosses Dihybrid cross- examine the inheritance of two different traits 6.17 p186

= Probability Probability number of ways a specific event can occur number of total possible outcomes Heredity patterns can be calculated with probability. Explain how Mendel’s laws relate to probability.