Non-Mendelian Genetics

Transcription

1 Non-Mendelian Genetics

2 Jan 3 rd Non-Mendelian Genetics Incomplete Dominance Codominance Practice handout Jan 4 th Multiple Alleles Polygenic Traits Sex-Linked Traits Jan 5 th Quiz Chromosome structure, karyotypes, introduction to genetic disorders

3 Mendelian Genetics: Dominant & Recessive Review One allele is DOMINANT over the other (because the dominant allele can mask the recessive allele) genotype: PP phenotype: purple genotype: pp phenotype: white genotype: Pp phenotype: purple

4 Review Problem: Dominant & Recessive In pea plants, purple flowers (P) are dominant over white flowers (p). Show the cross between two heterozygous plants. GENOTYPES: - PP (25%) Pp (50%) pp (25%) - ratio 1:2:1 PHENOTYPES: - purple (75%) white (25%) - ratio 3:1 P p P PP Pp p Pp pp

5 Incomplete Dominance a third (new) phenotype appears in the heterozygous condition as a BLEND of the dominant and recessive phenotypes. Ex - Dominant Red (R) + Recessive White (r) = Hybrid Pink (Rr) RR = red rr = white Rr = pink

6 Problem: Incomplete Dominance Show the cross between a pink and a white flower. GENOTYPES: - RR (0%) Rr (50%) rr (50%) - ratio 1:1 r r PHENOTYPES: - pink (50%); white (50%) - ratio 1:1 R Rr Rr r rr rr

7 Codominance in the heterozygous condition, both alleles are expressed equally with NO blending! Represented by using two DIFFERENT capital letters. Example: Dominant Black (B) + Dominant White (W) = Speckled Black and White Phenotype (BW) Sickle Cell Anemia - NN = normal cells SS = sickle cells NS = some of each

8 Codominance Example: Speckled Chickens BB = black feathers WW = white feathers BW = black & white speckled feathers Notice NO GRAY! NO BLEND! Each feather is either black or white

9 Codominance Example: Rhodedendron R = allele for red flowers W = allele for white flowers Cross a homozygous red flower with a homozygous white flower.

10 Codominance Example: Roan cattle cattle can be red (RR all red hairs) white (WW all white hairs) roan (RW red and white hairs together)

11 Codominance Example: Appaloosa horses Gray horses (GG) are codominant to white horses (WW). The heterozygous horse (GW) is an Appaloosa (a white horse with gray spots). Cross a white horse with an appaloosa horse. G W GW W GW W WW WW

12 Problem: Codominance Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. N S GENOTYPES: - NS (50%) SS (50%) - ratio 1:1 PHENOTYPES: - carrier (50%) sick (50%) - ratio 1:1 video S S NS NS SS SS

13 Incomplete & Codominance practice Due by the end of the hour today (1/3/18)

14 Multiple Alleles Jan 4 th there are more than two alleles for a gene. Ex blood type consists of two dominant and one recessive allele options. Allele A and B are dominant over Allele O (i)

15 Multiple Alleles: Lab Mouse Fur Colors Fur colors (determined by 4 alleles): black agouti yellow

16 Multiple Alleles: Rabbit Fur Colors Fur colors (determined by 4 alleles): full, chinchilla, himalayan, albino

17 Multiple Alleles: Blood Types (A, B, AB, O) Rules for Blood Types: A and B are co-dominant (Both show) AA or I A I A = type A BB or I B I B = type B AB or I A I B = type AB A and B are dominant over O (Regular dom/rec) AO or I A i = type A BO or I B i = type B OO or ii = type O

18 Multiple Alleles: Blood Types (A, B, AB, O)

19 O ii O A, B, AB, O O Phenotype Possible Genotype(s) Allele (antigen) on RBC surface Can Donate Blood To Can Receive Blood From A B I A i I A I A A A, AB A, O I B i I B I B B B, AB B, O AB I A I B AB AB A, B, AB, O

20 Problem: Multiple Alleles Show the cross between a mother who has type O blood and a father who has type AB blood. GENOTYPES: - I A i (50%) I B i (50%) - ratio 1:1 I A i I A i i I A i PHENOTYPES: - type A (50%) type B (50%) - ratio 1:1 I B I B i I B i

21 Problem: Multiple Alleles Show the cross between a mother who is heterozygous for type B blood and a father who is heterozygous for type A blood. GENOTYPES: -I A I B (25%); I B i (25%); I A i (25%); ii (25%) - ratio 1:1:1:1 I B I A I A I B i I B i PHENOTYPES: -type AB (25%); type B (25%) type A (25%); type O (25%) - ratio 1:1:1:1 i I A i ii

22 Jan. 5, 2018 Go over yesterday s assignment Quiz Discuss polygenic and sex-linked traits Assignment over sex-linked traits

23 Jan. 5, Quiz 1. Give an example of how incomplete dominance is different from codominance. 2. Is blood type O a) the universal donor or b) universal receiver? 3. Complete a Punnett square for a female who is heterozygous for type A blood and a male who has type AB blood. (Be sure to include genotypic and phenotypic ratios.)

24 Polygenic Traits traits produced by multiple genes example: skin color

25 Sex-Linked Traits Gene is attached to the X chromosome only, not found on the Y chromosome at all. (women have XX, men have XY chromosomes). These disorders are more common in boys. examples: red-green colorblindness

26 Sex-Linked Traits in males, there is no second X chromosome to mask a recessive gene. If they get an X with the disorder, they have it. Girls must inherit defective X s from both parents.

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28 Sex-Linked Traits A: 29, B: 45, C: --, D: 26 Normal vision A: 70, B: --, C: 5, D: -- Red-green color blind A: 70, B: --, C: 5, D: 6 Red color blind A: 70, B: --, C: 5, D: 2 Green color blind

29 Example of sex-linked trait Punnett Square Female who is not colorblind, but is a carrier. [XX c ] Male who is not colorblind. [XY]