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Mendelian Genetics

Mendelian Genetics. Gregor Mendel. Austrian Monk Cross breed different varieties of pea plants in order to create new characteristics Kept records and ratios of thousands of offspring

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Mendelian Genetics

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  1. Mendelian Genetics

  2. Gregor Mendel • Austrian Monk • Cross breed different varieties of pea plants in order to create new characteristics • Kept records and ratios of thousands of offspring • Found specific ratios which led him to believe that each fertilization had a chance outcome with a certain probability

  3. Gene: • Hereditary units for specific traits that are found on a specific location (locus) on a chromosome • Diploid cells have a pair of genes for each trait, on a pair of homologous chromosomes • NON-DUPLICATED HOMOLOGOUS CHROMOSOMES 

  4. Allele: • Different molecular forms for the same trait

  5. Dominant Allele • A trait that is always expressed • Masks recessive traits • Expressed as capital letters, ex: A

  6. Recessive Allele • A trait that is only expressed when both alleles are recessive • Expressed as lower case letters, ex: a

  7. Homozygous: • When both alleles are the same • Ex: AA (homozygous dominant) or aa (homozygous recessive)

  8. Heterozygous • Having two alleles for different traits • Aa

  9. Genotype • The genetic make up or code of an organism (can not see)

  10. Phenotype • The physical expression of ones genotype • (can see)

  11. Mendel’s Pea Traits:

  12. Mendel’s Pea Traits

  13. Mendel’s Pea Traits

  14. Write in the possible genotypes:

  15. Punnett Square • Method of predicting the probable outcome of a genetic cross

  16. Alleles from each parent are brought down, remember alleles from each parent are split into gametes during meiosis. Monohybrid Cross: Rr & Rr Each allele is brought down into the boxes to form the possible genotypes of the offspring • Genotype Ratio: 1:2:1, • Homozygous Dominant:Heterozygous: Homozygous Recessive • Phenotype Ratio: 3:1, Round:Wrinkled • Therefore there is a 75% chance of having offspring with round seeds and 25% chance of wrinkled seeds

  17. Dihybrid Cross: RrGg vs. RRgg

  18. Practice: • Heterozygous round versus wrinkled • Homozygous yellow seed versus green • Homozygous tall plant versus a homozygous short plant • Wrinkled seed plant versus a heterozygous round seed plant • A homozygous tall with homozygous yellow seeds versus a homozygous short with homozygous green seeds

  19. Practice: • TtYy vs. TtYy • State the genotype and phenotype ratios in addition to a punnett square • Genotype Ratios: • 1 TTYY, 2 TTYy, 2 TtYY, 4 TtYy, 2 Ttyy, 2 ttYy, 1 TTyy, 1 ttYY, 1 ttyy • 1:2:2:4:2:2:1:1:1 • Phenotype Ratios: • 9 tall with yellow seeds, 3 short with yellow seeds, 3 tall with green seeds, 1 short with green seeds • 9:3:3:1

  20. Pedigree • A method of genetic analysis using a family tree like diagram • Used to trace and predict outcomes of offspring

  21. Pedigree Practice Problem: Recessive because it would have shown through here Is lung disease dominant or recessive? How do you know? Label as many people as possible with their genotypes Ll or LL ll ll Ll Ll Ll Ll Ll ll Ll ll Ll Ll Ll or LL ll

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