Mendelian Genetics

Father of Modern Genetics Austrian monk, high school teacher, and part-time garden keeper First to propose biological inheritance of traits Work not recognized until after his death Gregor Mendel

Why pea plants? It’s what he had They grow fast Pea plants are true breeding Gregor noticed that one stock of seed would produce only tall plants and another only short plants

Traits… Specific characteristics that vary from one individual to the next – Hair color – Eye color – Seed color – Flower color

P generation Cross-pollination Next, Mendel wanted to find out if the white alleles had disappeared, or were they still present in the F1 generation. Mendel’s Experiment

Vocabulary… P generation: parental F1: “first son” – the offspring of the P generation F2: “second son” – the offspring of the F1 cross Phenotype: the physical characteristics, what the trait “looks” like Hybrid: cross between parents with different versions of the trait.

Mendel crossed the F1 generation with itself He found that the white flower trait reappeared in some of the F2 generation

Perplexed? Conclusion One: inheritance is due to factors that are passed from one generation to the next – Today, we call those factors GENES – Allele: different forms of a gene (like pink vs white for flower color) Conclusion Two: some alleles are dominant and others are recessive

How did the white trait “reappear”? He proposed this was due to segregation of alleles during formation of gametes. What are these called?! What are these called? What process made them?

Homozygous: two copies of the same allele – Dominant: AA – Recessive: aa – TRUEBREEDING Heterozygous: different alleles (Aa)

Practice: Cats 1.What trait is represented by “T” and “t”? 2.“NN” = phenotype or genotype? 3.Long hair = phenotype or genotype? 4.A homozygous tabby cat would have what genotype? 5.A cat that is “nn” would have what phenotype?

Applying and practicing your vocab Crazy Traits Exit Slip Vocab quiz on Wednesday

Probability Mendel categorized and counted the many offspring of each of his experiments. He noticed that each time he repeated a particular cross he obtained similar results. For example: Every time he crossed two plants that were heterozygous for stem height (Tt), about ¾ of the offspring were tall and ¼ were short.

Probability and Punnett Squares Punnett squares are used as a tool to predict this probability Monohybrid crosses can be performed to determine probability of phenotype for one particular trait

Genotypes AA Aa aa Homozygous Dominant Heterozygous Homozygous Recessive