1 / 22

Genetic Crosses

Genetic Crosses. Section 9.2. Genotype. The genetic makeup of an organism Consists of the alleles that the organism inherits from its parents Example: white flowering pea plants (recessive trait pp ). Phenotype.

loman
Download Presentation

Genetic Crosses

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Genetic Crosses Section 9.2

  2. Genotype • The genetic makeup of an organism • Consists of the alleles that the organism inherits from its parents • Example: white flowering pea plants (recessive trait pp)

  3. Phenotype • The appearance of an organism as a result of its genotype • Example: pea plants that are PP or Pp will have purple flowers

  4. Homozygous • Both alleles of a pair are alike • May be homozygous dominant (PP) or homozygous recessive (pp)

  5. Heterozygous • The two alleles in the pair are different • Example: a pea plant that is heterozygous for flower color would be Pp (purple flowers)

  6. Probability • The likelihood that a specific event will occur • May be expressed as a decimal, a percentage, or a fraction

  7. Probability = number of times an event is expected to happen_____________ number of opportunities for an event to happen

  8. Example: yellow pea seeds appeared 6022 times and green pea seeds appeared 2001 times in the F2 Total (6022 + 2001 = 8023) What is the probability that the dominant trait will appear in a similar cross? P = 6022 = .75 (or 75% or ¾ ) 8023

  9. Monohybrid Cross • A cross between individuals that involves one pair of contrasting traits • Example: crossing a pea plant that is pure for white flowers (pp) with one that is pure for purple flowers (PP)

  10. Punnett Square • Diagram used to predict the outcome of certain crosses • Predicts the probability of inherited traits

  11. Homozygous X Homozygous white flower (pp) p p purple flower (PP) P Pp Pp P Pp Pp

  12. Homozygous X Heterozygous black coat (Bb) B b black coat (BB) B BB Bb B BB Bb

  13. Heterozygous X Heterozygous black coat (Bb) B b black coat (Bb) B BB Bb b Bb bb

  14. Testcross • An individual of an unknown genotype is crossed with a homozygous recessive individual • Can be used to determine the genotype of any individual whose phenotype is dominant (example: BB or Bb)

  15. Incomplete Dominance • Occurs when two or more alleles influence the phenotype • Example: four o’clock flowers RR = red Rr = pink rr = white

  16. Incomplete Dominance in Four O’clock Flowers Pink flower (Rr) R r Pink flower (Rr) R RR Rr r Rr rr Phenotypic ratio: 1 red: 2 pink:1 white

  17. Codominance • Occurs when both alleles for a gene are expressed in a heterozygous offspring • Neither allele is dominant or recessive • Example: roan horses R = red coat (RR`) R` = white

  18. Dihybrid Cross • A cross between individuals that involves two pairs of contrasting traits • Must consider how the four alleles from each parent can combine

  19. Homozygous X Homozygous wrinkled & green (rryy) ry ry ry ry round & RY RrYyRrYy RrYy RrYy yellow RY RrYy RrYy RrYy RrYy (RRYY) RY RrYy RrYy RrYy RrYy Ry RrYy RrYy RrYy RrYy

  20. Heterozygous X Heterozygous round & yellow (RrYy) RY Ry rY ry round & RY RRYY RRYy RrYY RrYy yellow Ry RRYy RRyy RrYy Rryy (RrYy) rY RrYY RrYy rrYY rrYy ry RrYy Rryy rrYy rryy

  21. Four Phenotypes 9/16 round & yellow (genotypes RRYY, RRYy, RrYY, and RrYy) 3/16 round & green (genotypes RRyy and Rryy) 3/16 wrinkled & yellow (genotypes rrYY and rrYy) 1/16 wrinkled & green (genotype rryy)

  22. STUDY! • STUDY! STUDY! STUDY! STUDY! • STUDY! STUDY! STUDY! STUDY! • STUDY! STUDY! STUDY! STUDY! • STUDY! STUDY! STUDY! STUDY! • STUDY! STUDY! STUDY! STUDY!

More Related