Patterns of Inheritance - Mystery of Heredity Before the...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Mystery of Heredity - Before the 20th century, 2 concepts were the basis for ideas about heredity - Heredity occurs within species - Traits are transmitted directly from parent to offspring - Thought traits were born through fluid and blended in offspring - Paradox — if blending occurs, why don’t all individuals look like? Early Work - Josef Kolreuter (1760) — crossed tobacco strains to produce hybrids that differed from both parents - Additional variation observed in 2nd generation offspring contradicts direct transmission - T.A. Knight (1823) — crossed 2 varieties of garden pea, Pisum sativa - Crossed 2 true breeding strains - 1st generation resembled only 1 parent strain - 2nd generation resembled both Gregor Mendel - Chose to study pea plants because - Other research showed that pea hybrids could be produced - Many pea varieties were available - Peas are small plants and easy to grow - Peas can self-fertilize or be cross-fertilized Mendel’s Experimental Method - Usually 3 stages - Produce true-breeding strains for each trait he was studying - Cross-fertilize true-breeding strains having alternate forms of a trait - Also form reciprocal crosses - Allow the hybrid offspring to self-fertilize for several generations and count the number of offspring showing each form of the trait Monohybrid Crosses - Cross to study only 2 variations of a single trait - Mendel produced true-breeding pea strains for 7 different traits - Each trait had 2 variants
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
F1 Generation - First filial generation - Offspring produced by crossing 2 true-breeding strains - For every trait Mendel studied, all F1 plants resembled only 1 parent - Referred to this trait as dominant - Alternative trait was recessive - No plants with characteristics intermediate between the 2 parents were produced F2 Generation - Second filial generation - Offspring resulting from the self-fertilization of F1 plants - Although hidden in the F1 generation, the recessive trait had reappeared among some F2 individuals - Counted proportions of traits - Always found about 3:1 ratio
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern