Predict and interpret patterns

of inheritanceGenetics Unit

What is heredity?The passing on of characteristics (traits) from parents to offspringGenetics is the study of heredity

ProbabilityThe likelihood that a particular event will occur.

The principle of probability can be used to predict the outcome of genetic crosses.

Rule of Unit FactorsEach 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 AllelesThe trait that is always expressed if at least one allele is present in the offspring.

Represented by a capital LetterRecessive 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 DominanceOne 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.