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Fundamentals of genetics presentation

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Leucism in the American Alligator


Monastery at Brno where he grew his peas.


Genetics is the field of biology devoted to understanding how characteristics are transmitted from parents to offspring.Genetics was founded with the work of Gregor Johann Mendel in the mid 1800’s.

Austrian monk who experimented with garden peas.Mendel’s knowledge of statistics later proved valuable in his research on heredity—the transmission of characteristics from parents to offspring.

Contrasting traitsQuick growthProduce a lot of offspringPollination can be controlled: self-pollination and cross-pollination.

Why pea plants?

Mendel observed seven characteristics of pea plants:Plant Height: Tall/ShortFlower Color: Purple/WhiteFlower Position: Axial/Terminal

4. Seed Color: Yellow/Green5. Seed Texture: Smooth/Wrinkled6. Pod Shape: Inflated/Constricted7. Pod Color: Green/Yellow

He began by growing plants that were pure for each trait.Through self-pollination, Mendel developed 14 pure strains.He called each strain a parental generation, or P1 generation.


Mendel then cross-pollinated these strains.When the plants matured, he recorded the number of each type of offspring produced by each P1 plant. Mendel called the offspring of the P1 generation the first filial generation, or F1 generation.

He then allowed the flowers from the F1 generation to self-pollinate and collected the seeds. Mendel called the plants in this generation the second filial generation, or F2 generation.

1. Traits are controlled by factors: Alternate forms of genes called alleles.2. Some factors are dominant and some recessive: G or g 3. Law of Dominance


Dominant vs RecIn humans

4. Law of Segregation: Parent can only give one gene per trait: A or a not Aa5. Law of Ind. Assortment: Genes do not travel together: Eye color and toe size are not related


Law of Segregation your parent can only give you 1 of each!

Law of Ind. Assortment:

genotype: (gg, Gg, GG) The genetic makeup of an organism.phenotype: (green or yellow seeds) what it looks like


homozygous for a characteristic: GG or gg. Both alleles are the same (homo)heterozygous for a characteristic: Gg. Alleles for the trait are different (hetero)Name each of the following:AaAAaa

Probability is the likelihood that a specific event will occur.

75%¾ or 3:1 ratio

The ratio of the genotypes that appear in offspring is called the genotypic ratio.The ratio of the offsprings’ phenotypes is called the phenotypic ratio.


A cross between individuals that involves one pair of contrasting traits is called a monohybrid cross.


Punnett squares aid in predicting the probability that certain traits will be inherited by offspring.

A testcross can determine the genotype of any individual whose phenotype is dominant.


Sometimes the F1 offspring will have a phenotype in between that of the parents, a relationship called incomplete dominance.


Codominance occurs when both alleles for a gene are expressed in a heterozygous offspring.


A dihybrid cross is a cross between individuals that involves two pairs of contrasting traits.