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Mendel

Mendel. Review from Yesterday. With an elbow partner, define the following terms in your own words, without using your journal. Dominant Recessive Phenotype Genotype Heterozygote Homozygote. Mendel’s Work.

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Mendel

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  1. Mendel

  2. Review from Yesterday • With an elbow partner, define the following terms in your own words, without using your journal. • Dominant • Recessive • Phenotype • Genotype • Heterozygote • Homozygote

  3. Mendel’s Work • Chose to study characteristics that had 2 distinct forms (e.g flower color, seed color, seed shape, etc.) • Used true-breeding plants (plants that produced offspring identical to parent when self fertilized) • Crossed different true breeding plants with each other to see what would happen

  4. Mendel’s Work Contd. • Offspring of 2 true breeding parents is a hybrid. • Cross is the name for cross-fertilization • P generation is parental generation • F1 generation-hybrid offspring from P generation • F2 generation-offspring from F1 generation

  5. Mendel’s Hypotheses • There are alternative forms of genes, the units that determine heritable traits. The alternative forms of genes are called alleles. • For each inherited characteristic, and organism inherits 2 alleles, one from each parent. These alleles may be the same or different. An organism that has 2 identical alleles is said to be homozygous, and organism that has 2 different alleles for a gene is said to be heterozygous for that gene

  6. Mendel’s Hypotheses Contd. • If the two alleles of an inherited pair differ, than one determines an organism’s appearance and is called dominant; the other has no noticeable effect on the appearance and is called recessive. • A sperm or egg only carries on allele for each inherited characteristic because the 2 members of an allele pair segregate (separate) from each other during the production of gametes. This is the law of segregation. Egg and sperm unite at fertilization which restores the paired alleles in the offspring.

  7. Monohybrid Cross vsDihybrid Cross • Monohybrid: Mating of parental generations differing in one trait • Dihybrid: Mating of parental generations differing in 2 traits

  8. A dihybrid cross is essentially two monohybrid crosses occurring at the same time • Mendel assumed there would be a phenotypic ratio of 3:1 with dihybrid crosses

  9. Actually found that it was a 9:3:3:1 ratio, or two 3:1 ratios occurring simultaneously

  10. Law of Independent Assortment • Each pair of alleles assorts independently of the other pairs of alleles during gamete formation • In other words, the inheritance of one characteristic has no effect on the inheritance of another characteristic

  11. Pop Quiz • Define allele in your own words. • If an individual has a genotype of AA, are they heterozygous or homozygous? If homozygous, are they dominant or recessive? • Brown eyes (B) is dominant to blue eyes (b). Write a genotype for a brown eyed individual. • Using the info from question 3, what is the phenotype of an individual with the genotype bb? • What is a monohybrid cross?

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