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PUNNET Square NOTES for ISN 49

PUNNET Square NOTES for ISN 49. Genetics – study of how traits are passed from parent to offspring. Stems for Heredity :. When both alleles of a pair are the same it is said to be homozygous or a purebred. TT is homozygous dominant tt is homozygous recessive

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PUNNET Square NOTES for ISN 49

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  1. PUNNET Square NOTES for ISN 49

  2. Genetics – study of how traits are passed from parent to offspring

  3. Stems for Heredity:

  4. When both alleles of a pair are the same it is said to be homozygous or a purebred. • TT is homozygous dominant • tt is homozygous recessive • If there is one dominant and one recessive gene is isheterozygous or a hybrid. • Tt is heterozygous BB – Black Bb – Black w/ white gene bb – White

  5. Detached Earlobes are Dominant over

  6. Using Punnett Squares to predict monohybrid traits. Offspring inherit traits from parents: • Genes for a specific trait come in pairs. • Since each parent usually has two alleles for a single trait, we use a Punnett square to predictthe combinations of alleles in the offspring. • Punnett square is a tool used to predict the percentage or ratio of different genotypes an offspring could have.

  7. In a Punnett square, the top of the square shows the alleles of one parent and the side of the square show the other parent. Brown eyes show dominance over green eyes. http://feistyhome.phpwebhosting.com/punnett4.gif

  8. END of ISN 49 Notes

  9. Fire breathing Dragons Monohybrid Cross. • http://tcet.unt.edu/tegs/chapter2/fires.html

  10. Monohybrid Cross

  11. Example: A man and woman, both with brown eyes (B) marry and have a blue eyed (b) child. What arethe genotypes of the man, woman and child? • BbXBb Man = Bb Woman = Bb B b B b

  12. Cross 2 hybrid mice and give the genotypic ratio and phenotypic ratio. BbX Bb B b B b Genotypic ratio = 1 BB : 2 Bb : 1 bb 25% BB : 50% Bb : 25% bb Phenotypic ratio = 3 black : 1 white 75% black : 25% white

  13. Incomplete dominance • When one allele is NOT completely dominant over another (they blend) – incomplete dominance Example: In carnations the color red (R) is incompletely dominant over white (W). The hybrid color is pink. Give the genotypic and phenotypic ratio from a cross between 2 pink flowers. RWX RW R W R W Genotypic = 1 RR : 2 RW : 1 WW Phenotypic = 1 red : 2 pink : 1 white

  14. Examples of recessive genes disorders: • colorblindness – inability to distinguish between certain colors You should see 58 (upper left), 18 (upper right), E (lower left) and 17 (lower right). Color blindness is the inability to distinguish the differences between certain colors. The most common type is red-green color blindness, where red and green are seen as the same color.

  15. Example: A female that has normal vision but is a carrier for colorblindness marries a male with normalvision. Give the expected phenotypes of their children. N = normal vision n = colorblindness XNXnXXN Y XN Xn XN Y Phenotype: 2 normal vision females 1 normal vision male 1 colorblind male

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