Introduction to GeneticsIntroduction to Genetics

HeredityHeredity

Also know as Biological inheritance.Also know as Biological inheritance. It is the key to differences between species.It is the key to differences between species. The branch of biology that studies heredity The branch of biology that studies heredity

is called is called GeneticsGenetics..

History of HeredityHistory of Heredity Gregor MendelGregor Mendel- Monk who worked with pea plants to better - Monk who worked with pea plants to better

understand heredity, sometimes referred to as the father of understand heredity, sometimes referred to as the father of modern genetics, came up with modern genetics, came up with Principle of DominancePrinciple of Dominance..

The principle of dominance states that some alleles are The principle of dominance states that some alleles are dominantdominant and some are and some are recessive.recessive.

The The dominantdominant alleleallele is seen when in combination with is seen when in combination with itself or a recessive allele.itself or a recessive allele.

The The recessive allelerecessive allele is never seen when in combination with is never seen when in combination with the dominant, it is only seen with in combination with itself.the dominant, it is only seen with in combination with itself.

This doesn’t apply to all genes.This doesn’t apply to all genes.

Definitions of Mendel’s WorkDefinitions of Mendel’s Work

Purebred-Purebred- Produces offspring identical to Produces offspring identical to the parent. the parent.

Trait-Trait- Easily observable characteristic Easily observable characteristic (shape, color, size, etc.)(shape, color, size, etc.)

Hybrids-Hybrids- Organism produces by crossing Organism produces by crossing parents with differing characteristics.parents with differing characteristics.

Gene-Gene- Factor that controls traits. Factor that controls traits. Alleles-Alleles- The different forms of a gene. The different forms of a gene.

Definitions of SegregationDefinitions of Segregation

PhenotypePhenotype- Physical characteristic of an - Physical characteristic of an organism, the visible expression of an allele.organism, the visible expression of an allele.

GenotypeGenotype- Genetic makeup of an organism, the - Genetic makeup of an organism, the actually allele combination.actually allele combination.

HomozygousHomozygous- An organism that has two identical - An organism that has two identical alleles for a particular trait.alleles for a particular trait.

HeterozygousHeterozygous- An organism that has two different - An organism that has two different alleles for a particular trait.alleles for a particular trait.

SegregationSegregation We use a We use a Punnett SquarePunnett Square to visualize and predict to visualize and predict

the outcome of crossings. Punnett squares are used the outcome of crossings. Punnett squares are used to predict the probability of a cross without to predict the probability of a cross without actually crossing organisms.actually crossing organisms.– Single FactorSingle Factor– Double FactorDouble Factor

Segregation-Segregation- The separation of alleles during The separation of alleles during gamete formation. gamete formation.

The Two-Factor Crosses on The Two-Factor Crosses on Punnett Squares Punnett Squares

If two genes are connected in some way If two genes are connected in some way then the dominant alleles and recessive then the dominant alleles and recessive alleles will be segregated as matched sets alleles will be segregated as matched sets into gametes.into gametes.

If genes are not connected then they should If genes are not connected then they should segregate independently or undergo segregate independently or undergo Independent AssortmentIndependent Assortment..

ProbabilityProbability- The likelihood that a - The likelihood that a particular event can occur.particular event can occur.