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Genetics & The Work of Mendel

Genetics & The Work of Mendel. ____ ________________ ____________________ P airs of matching chromosomes, with one being inherited from each parent. (P). Chromosome from DAD: P. Chromosome from MOM: p. (p). ALLELES - _______________________________________________________.

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Genetics & The Work of Mendel

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  1. Genetics&The Work of Mendel

  2. ____________________ ____________________ Pairs of matching chromosomes, with one being inherited from each parent.

  3. (P) Chromosome from DAD: P Chromosome from MOM: p (p)

  4. ALLELES- _______________________________________________________.   Alleles for a trait are located at corresponding positions on homologous chromosomes called _______________. ALLELES Chromosome from MOM A b C d e Chromosome from DAD A B c d E

  5. When 1 allele masks (hides) the effect of another, that allele is called ________________and the hidden allele is called_____________. Dominant alleles are represented by a _________ letter Recessive alleles are represented by a _________ letter

  6. What are Dominant Genes? Hereford: ___________________________ Dominant: WW or Ww Recessive: ww ONLY

  7. What are Recessive Genes? • ___________________________. Dominant: PP or Pp Recessive: pp ONLY

  8. PHENOTYPE (___________________________________________) how the trait physically shows up in the organism; it is the observable Examples of phenotypes: blue eyes, brown fur, striped fruit, yellow flowers

  9. GENOTYPE ______________________________________________. As a result of sexual reproduction, there are 2 letters in the genotype __________________________________________ __________________________________________ 3 possible GENOTYPES: 2 capital letters (like "TT") – ______________________ 1 of each ("Tt") - _____________________ 2 lowercase letters ("tt") – ________________________

  10. Gregor Mendel (1822-1884) Austrian monk Called the “______________ ___________________" for his study of the inheritance of _______ in pea plants.

  11. Mendel collected data for 7 pea traits

  12. Gregor Mendel (1822-1884) Mendel's work was not recognized until the turn of the 20th century

  13. Mendel’s work Pollen transferred from white flower to stigma of purple flower • Bred pea plants • cross-pollinate _____________________ • raised seed & then observed traits • allowed offspring to __________________& observed next generation all purple flowers result self-pollinate ?

  14. true-breeding purple-flower peas true-breeding white-flower peas 100% purple-flower peas 1st generation (hybrids) 100% 75% purple-flower peas 25% white-flower peas 3:1 2nd generation Looking closer at Mendel’s work X Parents self-pollinate

  15. Homozygous-dominant PP x pp P P p p Homozygous-recessive

  16. all the F1 (1st filial generation) offspring are ______________________________ 100% purple offspring

  17. Heterozygous - hybrid Pp x Pp P p P p Heterozygous - hybrid

  18. the F2 (2nd filial generation) shows a 3:1 ratio, with ________________________________________ P p Phenotypic ratio: ______________________ Genotypic ratio ______________________ P p

  19. What did Mendel’s findings mean? • Some traits mask others • purple & white flower colors are separate traits that do not blend • purple x white ≠ light purple • _______________________ • __________________ • _______________________ • affects characteristic • masks other alleles • __________________ • _______________________ • allele makes a non-functioning protein I’ll speak for both of us! allele producingfunctional protein mutant allele malfunctioningprotein homologouschromosomes

  20. PP pp x X P purple white F1 all purple Making crosses • Can represent alleles as letters • flower color alleles  • true-breeding purple-flower peas  • true-breeding white-flower peas 

  21. PP male / sperm P p Pp P Pp female / eggs pp p Punnett squares Aaaaah, phenotype & genotypecan have different ratios 1st generation (hybrids) Pp x Pp % genotype % phenotype

  22. B b B Bb x Bb b Monohybrid Cross • Example:Cross between two ___________________________________ BB = brown eyes Bb = brown eyes bb = blue eyes

  23. B b 1/4 = BB - brown eyed 1/2 = Bb - brown eyed 1/4 = bb - blue eyed B Bb x Bb b Monohybrid Cross

  24. Dihybrid cross • Other of Mendel’s experiments followed the inheritance of 2 different characters • ________________________ • ________________________ Mendelwas working outmany of the genetic rules!

  25. F1 generation (hybrids) yellow, round peas F2 generation Dihybrid cross P true-breeding yellow, round peas true-breeding green, wrinkled peas x YYRR yyrr Y = yellow R = round y = green r = wrinkled YyRr self-pollinate 9/16 yellow round peas 3/16 green round peas 3/16 yellow wrinkled peas 1/16 green wrinkled peas

  26. RY Ry rY ry x RY Ry rY ry possible gametes produced Dihybrid Cross • Example:cross between round and yellow heterozygous pea seeds. R = round r = wrinkled Y = yellow y = green RrYy x RrYy

  27. RY Ry rY ry RY Ry rY ry Dihybrid Cross

  28. 9/16 yellow round YyRr YyRr 3/16 green round YR YR yr YR yR Yr yr Yr 3/16 yellow wrinkled yR 1/16 green wrinkled yr Dihybrid cross or YyRr x YyRr YR Yr yR yr  YYRR YYRr YyRR YyRr BINGO! YYRr YYrr YyRr Yyrr YyRR YyRr yyRR yyRr YyRr Yyrr yyRr yyrr

  29. RY Ry rY ry RY RRYY RRYy RrYY RrYy Ry RRYy RRyy RrYy Rryy rY RrYY RrYy rrYY rrYy ry RrYy Rryy rrYy rryy Dihybrid Cross

  30. Extending Mendelian genetics • Mendel worked with a simple system • peas are genetically simple • most traits are controlled by single gene • each gene has only 2 version • 1 completely dominant (A) • 1 recessive (a) • But its usually not that simple!

  31. Incomplete Dominance • Incomplete dominance is when both alleles are expressed and results in an __________________ ________________. The hybrid is _______________ ________________. • When expressing incomplete dominant alleles, _____________________________________________ _____________________________________________.

  32. Incomplete dominance • Hybrids have “in-between” appearance • RR = red flowers • rr = white flowers • Rr = pink flowers • make 50% less color RR WW RW RR Rr rr

  33. 100% pink flowers 1st generation (hybrids) 25% red 50% pink 25% white 2nd generation Incomplete dominance X true-breeding red flowers true-breeding white flowers P self-pollinate

  34. Homozygous IncompleteDominanceP (parental)generation R R W W Homozygous

  35. Incomplete Dominance F1 (First Filial) generation R R W W 100% pink offspring

  36. Heterozygous Incomplete DominanceF1 x F1 R W R W Heterozygous

  37. Incomplete DominanceF2 (Second Filial) generation R W R W

  38. RR male / sperm R W RW R RW female / eggs WW W Incomplete dominance RW x RW % genotype % phenotype RR RW RW WW

  39. Co-dominance • Some alleles are equally strong and neither are masked by the other. Alleles which are ________________________ are said to be “______________________". • The hybrid is ________________________________.

  40. Co-dominance

  41. Co-dominance

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