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Genetics

Genetics. Chapter 11. Genetics. Genetics is the study of heredity Every living thing- plant or animal, microbe or human being- has a set of characteristics inherited from its parent or parents. Gregor Mendel. “Father” of genetics Austrian monk, mid-1800s Researched pea plant inheritance

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Genetics

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  1. Genetics Chapter 11

  2. Genetics • Genetics is the study of heredity • Every living thing- plant or animal, microbe or human being- has a set of characteristics inherited from its parent or parents.

  3. Gregor Mendel • “Father” of genetics • Austrian monk, mid-1800s • Researched pea plant inheritance • Easy to grow, fast reproduction • Studied plant height, pea shape/color, pod color, etc.

  4. Pea Plant Fertilization • Self-pollination • Male gametes (pollen) fertilize egg of same flower • Produces pure-bred offspring, meaning that all characteristics are received from a single parent or plant • True-breeding: produce offspring identical to parent when self-pollinated

  5. Pea Plant Fertilization • Cross-pollination • Pollen from one plant fertilizes egg of another plant • Mendel had to prevent self-pollination in order to cross-pollinate. • He did this by cutting away the pollen-bearing male parts and dusting pollen from another plant into eggs of the flower. • Offspring have two parents

  6. Mendel’s Experiments • P = Parent generation • F1 = First filial generation • Filius = Latin for “sons” and “daughter” • F2 = Second filial generation (F1 X F1) P Pure Green X Pure Yellow F1 All Green F2 3 Green:1 Yellow

  7. Mendel’s Conclusions • Law of Dominance – one allele (form of a gene) is dominant, one is recessive • Recessive trait was hidden in F1 generation • Green = dominant • Yellow = recessive

  8. Mendel’s Conclusions • Law of Segregation: alleles for a gene separate (segregate) when gametes (sex cells) form (meiosis I) • Each F1 plant produces two types of gametes, in the Mendel’s pea pod case one allele for tallness and one for shortness

  9. Punnett Squares • First must determine possible gametes • Heterozygous tall plant = Tt • Half of gametes will get ‘T’, other half will get ‘t’ • Homozygous tall plant = TT • All gametes will get ‘T’

  10. Punnett Squares Tt X Tt • Monohybrid cross • Cross involving one trait • Gametes go on the top and side • Combine gametes to find possible offspring

  11. Punnett Squares Tt X Tt • Genotype (genetic make-up) ratio 1TT: 2Tt: 1tt Phenotype (physical characteristics) ratio 3 tall: 1 short

  12. Probability • Punnett squares are used to predict the probability of certain traits in offspring of genetic crosses • Tt X Tt • ½ chance of getting ‘t’ from mom, ½ chance of getting ‘t’ from dad • ½ X ½ = ¼ tt in offspring

  13. Dihybrid Cross • Mendel looked at the inheritance patterns of two traits • Seed shape and seed color • Found that the traits were inherited independently of each other • Law of Independent Assortment • Genes on separate chromosomes are inherited at random

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