Predict and interpret patterns of inheritance Genetics Unit

What is heredity?  The passing on of characteristics (traits) from parents to offspring  Genetics is the study of heredity

Probability  The likelihood that a particular event will occur.  The principle of probability can be used to predict the outcome of genetic crosses.

Rule of Unit Factors  Each organism has two alleles for each trait  Alleles - different forms of the same gene  Genes - located on chromosomes, they control how an organism develops

 Dominant Alleles  The trait that is always expressed if at least one allele is present in the offspring.  Represented by a capital Letter  Recessive Alleles  The trait that is only expressed if an organism has both recessive alleles.  Represented by a lower case letter.

Punnett Square  Punnett squares can be used to predict and compare the genetic variations that will result from a cross.  Homozygous – Organisms that have two identical alleles for a particular trait. (TT or tt)  Heterozygous – Organisms that have two different alleles for the same trait. (Tt)  Phenotype – physical characteristics (blue eyes)  Genotype – genetic makeup (alleles Tt, TT, tt)

Monohybrid Cross - crossing parents who differ in only one trait (AA with aa)

Punnett Square (Monohybrid)

Dihybrid Cross - crossing parents who differ in two traits (AAEE with aaee)

Punnett Squares (Dihybrid)

Incomplete Dominance  One allele is not completely dominant over the other allele.  The heterozygous phenotype is somewhere between the dominant and the recessive trait.

 Both alleles are dominant and show up in the phenotype. Codominance

 A gene with more than two alleles.  This only means that there are more than two forms of the trait. Multiple Alleles

 Traits controlled with two or more genes. Polygenic Traits

 Characteristics of any organism are a result of an interaction between genes and environment.  Genes provide a blueprint, but environmental factors can alter the finished product.