Ch.9 Patterns of inheritance Gregor Mendel. Mendel’s discoveries A Blending- Hereditary material- Both parents contribute genetic material. BInheritable

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  • Ch.9 Patterns of inheritance

    Gregor Mendel

  • Mendels discoveries

    Blending- Hereditary material- Both parents contribute genetic material.

    Inheritable factors, genes are passed from generation to generation

  • Pea experimentsWorked with 7 traitsUsed purebreeding plants first then crossed them.

  • Know the vocabularyHomozygous- TT or tt - the same versionHeterozygous- Tt- two different versionsPhenotype - What you see ( look like)Genotype - The genes TT,Tt, or tt

  • Mendels Pea Crosses

  • Law of independent assortment.

    homologous chromosomes move independently.Ex. Chromosome with A or a will go separate from chromosome with B or b.

  • Law of SegregationHomologous pairs segregate during gamete formation(meiosis) and pair again after fertilizationEx. If a pea is Pp then half the gametes will receive a P and half a p.

  • Testcross

  • Dihybrid Cross

  • Incomplete dominanceIncomplete dominance leads to a blending of traits, red + white yields pink

  • Codominance

  • CodominanceCodominance - A and B are both dominant to O but not to each other, giving the AB blood type

  • EpistasisOne gene has an effect on another. C leads to deposition of color while B or b leads to color BBcc would be white even though the genes code for black color.

  • Polygenic inheritanceCombinations of genes can yield cumulative effects. The more dominant alleles the more color.

  • Environmental EffectsSometimes the environment can change the way a gene is expressed, like these hydrangia, and the color based on pH of the soil.

  • PleiotropyOne gene can have an effect on other parts of the body. The sickle cell gene which causes problems with blood cells has far reaching affects on the body.

  • Sample problemsMendel crossed short and tall pea plants(purebred cross) TT x tt = P gen. t tT Tt Tt All offspring are heterozygousT Tt Tt All are tall (Tt)

  • Mendel crossed round, yellow pea plants to wrinkled, green pea plants (RRYY x rryy) The only possible gametes are RY from parent 1 and ry from parent 2 so ry ryRY RrYyRrYy All offspring are roundRY RrYy RrYy and yellow (RrYy)

  • Monohybrid Cross -two heterozygotes matedTt xTt T tT TT Tt 1TT:2Tt:1ttt Tt tt 3 tall: 1 short

  • Dihybrid crossHeterozygotes for 2 traits are crossed RrYy x RrYyYou can make the folowing gametes for each parent RY,Ry,rY,ry, this means a four by four box as in the next slide

  • Dihybrid Cross

  • Dihybrid crosses can also be done like this; R r Y yR RR Rr Y YY Yyr Rr rr y Yy yy

    Now calculate the chances of RRYY (1/4 x 1/4)RRYy (1/4 x2/4) RrYY (2/4 x 1/4)RRyy (1/4 x 1/4) RrYy ( 2/4 x 2/4)Rryy (2/4 x 1/4) rrYY (1/4 x/1/4)rrYy (1/4 x 2/4) rryy (1/4 x 1/4)