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03. multiple alleles
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- 2. Multiple Alleles • Foreach trait Mendel studied, there were only two possible alleles. The dominant allele controlled the trait. However, it is possible to have more than two alleles, this is called multiple alleles. • Geneticists that study fruit flies (Drosophila melanogaster), have seen many alleles for one gene. They use numbers to indicate which allele is dominant over another.
- 4. • In fruitflies the eye colors can be as follows: wild (E1E1), coral (E2E2), blood (E3E3), easin (E4E4), cherry (E5E5), apricot (E6E6), honey (E7E7), buff (E8E8), tinged (E9E9), pearl (E10E10), ivory (E11E11), white (E12E12) * The smaller number is dominant over a
- 5. • E.g Afruit fly heterozygous wild/blood mates with one heterozygous coral/easin, describe possible offspring eye color. • Parents: E1E3 * E2E4 F1 E1 E3 E2 E1E2 E2E3 E4 E1E4 E3E4 2 wild eye 1 coral eye 1 blood eye
- 6. Incomplete Dominance • Priorto Mendel’s studies, scientists believed that hybrids would have a blending of traits. Although Mendel never found examples of this, many do exist in nature. • When Red x white = pink, this is called intermediate inheritance (incomplete dominance) . • Another type of incomplete dominance is called co-dominance, where both alleles are expressed (Roan cows have red and white hair) • This is a contradiction to Mendel’s thought that one trait is always dominant over another
- 7. Law of IncompleteDominance • Both genes may be expressed E.g. If a plant breeding pure for red flowers crosses with one breeding pure for white flowers. Red and white are incompletely dominant producing pink flowers. Describe possible F1 and F2 generation offspring.
- 8. Pure red andpure white mate (F1) • Parents RR x WW = RW F1 R R W RW RW W RW RW Phenotype (what you see) – all pink
- 9. Pink and Pinkmate (F2) • Parents RW x RW F1 R W R RR RW W RW WW Phenotype (what you see) – 1 red 2 pink 1 white
- 10. 1. If aplant breeding pure for green leaf and pure for purple flower crosses with one breeding pure for white leaf and pure for white flower (green + white are incompletely dominant producing striped leaf and purple and white are incompletely dominant producing mauve flowers). Describe possible F1 and F2 generation offspring.
- 11. F2 GP GP WFWGPF WGPF WF WGPF WGPF GG PP x WW FF Phenotype – 100% are striped leaf and mauve flower Genotype – 100% WGPF G – green leaf P - purple flower W – white leaf F – white flower
- 12. F2 WP WFGP GF WP WW PP WW PF WG PP WG PF WF WW PF WW FF WG PF WG FF GP WG PP WG PF GG PP GG PF GF WG PF WG FF GG PF GG FF WG PF x WG PF Phenotype – 1 / 16 white seed, purple flower 2 / 16 white seed, mauve flower 1 / 16 white seed, white flower 2 / 16 striped seed, purple flower 4 / 16 striped seed, mauve flower 2 / 16 striped seed, white flower 1 / 16 green seed, purple flower 2 / 16 green seed, mauve flower 1 / 16 green seed, white flower Genotype – 1 / 16 WW PP 2 / 16 WW PF 1 / 16 WW FF 2 / 16 WG PP 4 / 16 WG PF 2 / 16 WG FF 1 / 16 GG PP 2 / 16 GG PF 1 / 16 GG FF
- 13. • A guineapig breeding pure for long hair and pure for cowlicks mates with one breeding pure for short hair and smooth coat (Long hair and short hair are incompletely dominant producing medium length hair, while cowlicks are dominant. • Describe possible F1 and F2 generation offspring.
- 14. F2 LC LC ScLSCc LSCc Sc LSCc LSCc LL CC x SS cc Phenotype – 100% are medium length with cowlicks Genotype – 100% LSCc L – Long hair C - cowlicks S – short hair c – smooth hair
- 15. F2 LC LcSC Sc LC LL CC LL Cc LS CC LS Cc Lc LL Cc LL cc LS Cc LS cc SC LS CC LS Cc SS CC SS Cc Sc LS Cc LS cc SS Cc SS cc LSCc x LSCc Phenotype – 3 / 16 long hair, cowlick 1 / 16 long hair, smooth 6 / 16 medium hair, cowlick 1 / 16 medium hair, smooth 3 / 16 short hair, cowlick 1 / 16 short hair, smooth Genotype – 1 / 16 LL CC 2 / 16 LL Cc 1 / 16 LL cc 2 / 16 LS CC 4 / 16 LS Cc 2 / 16 LS cc 1 / 16 SS CC 1 / 16 SS cc 2 / 16 SS Cc
- 16. • A plantbreeding pure tall, pure red flowers and pure green leaf, crosses with one pure short, pure white flower and pure yellow leaf. Underlined traits are dominant. Describe phenotype of possible F1 and F2 generation offspring. • Tri-hybrid cross
- 17. F2 TRG TRG trgTt Rr Gg Tt Rr Gg trg Tt Rr Gg Tt Rr Gg TT RR GG x tt rr gg Phenotype – 100% are tall with red flowers and green leaves Genotype – 100% Tt Rr Gg T – tall , t – short R – red flower, r – white flower G – green leaf, g – yellow leaf
- 18. F2 TRG TRG trgTt Rr Gg Tt Rr Gg trg Tt Rr Gg Tt Rr Gg Tt Rr Gg x Tt Rr Gg Phenotype – 100% are tall with red flowers and green leaves Genotype – 100% Tt Rr Gg T – tall , t – short R – red flower, r – white flower G – green leaf, g – yellow leaf