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Genetics

Genetics. Dyhybrid Crosses Objective 6-8. Law of Independent Assortment : two or more pairs of alleles segregate (separate) independently of one another during gamete formation.

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Genetics

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  1. Genetics

  2. Dyhybrid CrossesObjective 6-8 • Law of Independent Assortment: two or more pairs of alleles segregate (separate) independently of one another during gamete formation. • This implies that traits are NOT related to each other. In other words, when ________________ are formed, genes move into the gametes independently of other genes. • Example: gametes Height and eye color are NOT related

  3. Dyhybrid CrossesObjective 6-8 This is true ONLY if these genes are on __________________________________. Example: If 2 genes are on the same chromosome they __________ _____________ and the traits appear to be related to each other. Example: Separate Chromosomes If height is on chromosome #1 and eye color is on Chromosome #22 they move separately during meiosis. Move together If hair color is on chromosome #7 and eye color is on Chromosome #7 then they move together.

  4. Dyhybrid CrossesObjective 6-8 Dihybrid Cross: A genetic cross that shows the probability of inheriting 2 traits that are NOT related to each other (__________________________________)Dihybridcrosses are especially useful for people who breed pets. On Different Chromosomes

  5. Dyhybrid CrossesObjective 6-8 • Example 1: In a species of fictitious mice, black fur (B) is dominant to brown fur (b). Most mice run (R), however a recessive allele for this gene causes mice to hip-hop (r). Parents: BBRR X bbrr Possible Gametes: ***What will be the genotype for all offspring of these two parents? br BR BbRr

  6. Dyhybrid CrossesObjective 6-8 Notice that each parent produces gametes with alleles for 2 genes, one from each pair. Each gamete can only have __________________ from each parent for any given gene One allele

  7. Dyhybrid CrossesObjective 6-8 • Example 2: There are many snake breeders that try to breed for unusual colors and patterns. Shown below is a cross between two heterozygous green striped snakes (GgSs). These snakes also have the recessive genes for yellow color (g) and for solid pattern (s). Parents: GgSsX GgSs Possible Gametes: GS, Gs, gS, gs GS, Gs, gS, gs

  8. Punnett Square: p= GgSs X GgSs gS gs Gs GS GGSS GGSs GgSS GgSs GS Green, Striped Green, Striped Green, Striped Green, Striped Gs gS gs

  9. Dyhybrid CrossesObjective 6-8 What is the genotypic ratio? What is the phenotypic ratio? 1:2:2:4:1:2:1:2:1 9:3:3:1

  10. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 9-10 • Remember, in traditional Mendelian inheritance, an individual that is heterozygous will show the phenotype of the _________________ trait. Dominant

  11. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 9-10 1. Incomplete Dominance--the phenotype of the heterozygote is ___________ of the phenotypes of the 2 homozygotes. • Example: A Mix FlowerColorRR=red Rr=Pink rr=white

  12. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 9-10 2. Codominance--a heterozygous individual will express _______________ phenotypes. Example: both Chicken feather BB=black bb= white Bb= Black and white

  13. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 9-10 3. Polygenic Inheritance--a trait is controlled by ___________________ genes. • Examples: 2 or More Skin Color, Hair Color, Eye Color, Heights in humans

  14. Practice: Carefully examine each set of traits below and decide whether the trait is an example of: traditional inheritance (T), Codominance (C) or incomplete dominance (I). 1. Flower Color: PP=purple pp=white Pp=light purple ___________ 2. Coat Pattern: FF=freckles ff=stripes Ff=freckles & stripes __________ 3. Face Shape: RR=round rr=square Rr=round ____________ 4. Eye Size: LL=large ll=small Ll=medium ____________ 5. Eye Color: BB=brown bb=blue Bb=brown ____________ 6. Fur Color BB=black bb=white Bb=gray ____________ 7. Fur Color: OO=orange oo=white Oo=orange & white____________ I C T I T I C

  15. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 9-10 8. Use the information from question 6. If the mother is BB and the father is heterozygous, what are the genotypic and phenotypic ratios? Draw a Punnett square to support your answer. B B Geno: 50% BB, 50% Bb B BB BB Pheno: 50% black, 50% Grey Bb b Bb

  16. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 11 4. Multiple Alleles--a trait that has more than ________________________________. • Remember, an allele is __________________________________. • Example: 2 possible alleles (Choices) One version of a gene B= brown eyes b=blue eyes

  17. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 11 Blood type in humans is a trait that has multiple alleles. The gene for blood type has 3 possible alleles: A, B and O Rules: Each person still receives only 2 alleles! A and B are ________________________; O is __________________. Co-Dominant Recessive

  18. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 11 • Genotype Phenotype IAIA (AA) IAi (AO) IBIB (BB) IBi (BO) IAIB (AB) Ii (OO) A A B B AB O

  19. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 11 Examples: 1. A woman with bloodtype BO marries a man with bloodtype AO. Draw a Punnett square to show the possible phenotypes of their children. A O Pheno: 25% AB, 25% B 25% A, 25% O AB B BO AO OO O

  20. Non-Traditional InheritanceIncomplete Dominance, Codominance, Polygenic Traits and Multiple AllelesObjective 11 2. Can a couple with bloodtypes AB and O have a child with type O blood? Draw a Punnett square to prove it. A B Pheno: 50% A, 50% B O AO BO AO BO O

  21. PedigreesObjective 13-14 A genetic Family Tree Pedigree—

  22. I II = female =normal (RR) = Affected (rr) = male = Carrier (Rr)

  23. Sex Linked InheritanceObjective 12 • T.H. Morgan was a scientist who worked with _________ ___________. Most have red eyes (R), but one day he found some with __________ eyes. He thought he had found a new mutation. Fruit Flies white

  24. Sex Linked InheritanceObjective 12 The Test: Step 1 ___________ X ____________ Male (rr) Female (RR) r r Rr Rr R R Rr Rr red Result: All the flies had _____ eyes

  25. Sex Linked InheritanceObjective 12 Rr Rr Step 2 __________ X _____________ R r RR Rr R rr r Rr Expected Pheno: 3 red (75%), 1 white (25%)

  26. Sex Linked InheritanceObjective 12 red Result: All the females had _____ eyes. _______ the males had red eyes and _______ had white. Question: Why is there a difference in males and females? Answer: half half The gene of eye color in flies is on the X chromosome

  27. Sex Linked InheritanceObjective 12 Sex-Linked Traits—genes that are carried on one of the _______ chromosome ( ) and are therefore inherited differently in males and females. In all of the cases we will talk about the genes are on the ______ chromosome. sex X or Y X

  28. Sex Linked InheritanceObjective 12 Color Blindness Hemophilia and ______________________ in humans and eye color in flies are sex-linked traits.

  29. Sex Linked InheritanceObjective 12 Back to Morgan’s Flies: • In order to show that traits are inherited differently in males and females Morgan wrote the genotypes a little differently Possible Female Genotypes: Possible Male Genotypes: XRXR= red, XRXr=red, XrXr= white XRY= red, XrY= white

  30. Sex Linked InheritanceObjective 12 Does this explanation work? YES

  31. Sex Linked InheritanceObjective 12 P--White male X Red Female (RR) Xr Y Male = Red eyes Female= Red eyes XRXr XRY XR XR XRY XRXr

  32. Sex Linked InheritanceObjective 12 F1--Red male X Red Female XR Y Male= 50%red and 50% white Females= 100% red XRXr XRY XR Xr XrY XRXr

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