Mendel:Mendel:Fundamentals of Fundamentals of

GeneticsGenetics

Gregor MendelGregor Mendel

1850’s…Austrian Monk1850’s…Austrian Monk Studied science and math…Studied science and math…

researched heredity using pea researched heredity using pea plants.plants.

Heredity- passing of characteristics Heredity- passing of characteristics from parents to offspring.from parents to offspring.

Mendel’s ExperimentMendel’s Experiment

Mendel observed 7 different Mendel observed 7 different characteristics of pea plantscharacteristics of pea plants

He noticed each characteristic He noticed each characteristic occurred in 2 contrasting traitsoccurred in 2 contrasting traits

7 Characteristics Mendel 7 Characteristics Mendel StudiedStudied

Mendel’s Experiments:Mendel’s Experiments:

-Worked with -Worked with purepure plants, meaning always plants, meaning always producing offspring with the same trait.producing offspring with the same trait.

-Parental generation: P-Parental generation: P11 generation. generation.

-Offspring of the P-Offspring of the P11 generation = F generation = F11 generation. generation.

-Offspring of the F-Offspring of the F11 generation = F generation = F22 generationgeneration

3 Steps to Mendel’s 3 Steps to Mendel’s ExperimentExperiment

Rule of DominanceRule of Dominance

-Mendel concluded that one factor -Mendel concluded that one factor (allele) in a pair may prevent the (allele) in a pair may prevent the other from having an effect. He other from having an effect. He called this the called this the dominantdominant factor. factor.

-The allele that did not appear but -The allele that did not appear but appeared later was called the appeared later was called the recessiverecessive allele. allele.

Law of SegregationLaw of Segregation

-Mendel concluded that alleles -Mendel concluded that alleles separate during meiosis. This means separate during meiosis. This means that each gamete produced only that each gamete produced only received one allele of the pair. received one allele of the pair. When the gametes combine during When the gametes combine during fertilization, the offspring have two fertilization, the offspring have two alleles controlling a specific trait.alleles controlling a specific trait.

Law of Independent AssortmentLaw of Independent Assortment

-Mendel crossed plants that differed -Mendel crossed plants that differed in two traits. For example, flower in two traits. For example, flower color and seed color. He figured out color and seed color. He figured out that the alleles for different traits that the alleles for different traits are not connected and are are not connected and are distributed to gametes distributed to gametes independently. independently.

Chromosomes & GenesChromosomes & Genes

Genes- segment of DNA on a chromosome Genes- segment of DNA on a chromosome that controls a particular trait.that controls a particular trait.

Different forms of genes are called Different forms of genes are called alleles.alleles.

Letters are used to designate alleles. Letters are used to designate alleles. Capital letters = dominant alleles (G, T, H)Capital letters = dominant alleles (G, T, H)Lower case letters = recessive alleles (g, t, Lower case letters = recessive alleles (g, t, h)h)

Genotype- genetic makeup of an Genotype- genetic makeup of an organism. Consists of the alleles organism. Consists of the alleles that an organism inherits from its that an organism inherits from its parents. For example HH, Hh, or parents. For example HH, Hh, or hh.hh.

Phenotype- the physical appearance Phenotype- the physical appearance of an organism. (Example- purple of an organism. (Example- purple flowers.)flowers.)

Homozygous- both alleles of a pair Homozygous- both alleles of a pair are alike.are alike.

HH or hhHH or hh((Homozygous dominant or homozygous Homozygous dominant or homozygous

recessive)recessive)

Heterozygous- alleles of a pair are Heterozygous- alleles of a pair are different.different.

HhHh