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Topic: Modeling Inheritance

T. T. Tt. t. t. Topic: Modeling Inheritance. ¼. EQ: How can inheritance be modeled?. OBJECTIVE. THE STUDENT WILL DEMONSTRATE AN UNDERSTANDING OF HOW INHERITANCE CAN BE MODELED STUDENTS WILL DEMONSTRATE HOW TO USE A PUNNETT SQUARE TO MODEL INHERITANCE. STUDENT EXPECTATIONS.

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Topic: Modeling Inheritance

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  1. T T Tt t t Topic: Modeling Inheritance ¼ EQ: How can inheritance be modeled?

  2. OBJECTIVE • THE STUDENT WILL DEMONSTRATE AN UNDERSTANDING OF HOW INHERITANCE CAN BE MODELED • STUDENTS WILL DEMONSTRATE HOW TO USE A PUNNETT SQUARE TO MODEL INHERITANCE

  3. STUDENT EXPECTATIONS • Understand how to make predictions about possible outcomes of genetic combinations using an organisms inherited genotypes. T t TT Tt T T

  4. For each monohybrid cross, Mendel cross-fertilized true-breeding plants that were different in just one character—in this case, flower color. He then allowed the hybrids (the F1 generation) to self-fertilize.

  5. Mendel’s Conclusions of how often traits are passed!!!! • Mendel found that traits usually passed with the following ratios. • This was used to predict expected genetic outcomes He found that for every cross these results were found. ¾ 75% 3:1 (usually there were 3 traits for every one trait seen

  6. What controls traits?

  7. Chromosomes Homologous chromosome: one of a matching pair of chromosomes, one inherited from each parent. Sister chromatids are identical

  8. Genes Factors that are passed from one generation to the next… Genes come in different forms called alleles: ex: tall and short Some are seen and some are not

  9. DOMINANT/RECESSIVE Dominant capital _____________ allele is represented by a ____________ letter.(usually the first letter of the trait) ____________ allele is represented by the SAME _________________ letter. EX: Tall = ______ Short =______ Recessive lower-case Important: You will only see a recessive trait if you inherit two recessive traits. If not you will always see the dominant trait T t NOT S for short

  10. Phenotype • An organism’s physical traits • 1. Tall or short • Genotype • An organism’s genetic makeup • 1. Letters Tt or Tt

  11. HOMOZYGOUSHETEROZYGOUS When both alleles in the pair are the _______, the organism is _______________ or __________ EX: ____ or ___ When both alleles in the pair are _____________, the organism is _________________ or _____________ Ex: ____ SAME HOMOZYGOUS PUREBRED TT tt DIFFERENT HETEROZYGOUS HYBRID Tt

  12. PROBABILITY ____________________is the __________ that a particular _________________ likelihood event will occur It can be written as a: Fraction Percent ____ Ratio 1/4 25% 1:3

  13. http://www.arborsci.com/CoolStuff/CoinFlip.jpg COIN FLIP capital There are 2 possible outcomes: HEADS TAILS The chance the coin will land on either one is: ____ ____ ____ Alleles segregate randomly just like a coin flip. . . So can use probability to predict outcomes of genetic crosses. 1/2 50% 1:1

  14. TOOLS FOR MODELING INHERITANCE PARENT’SGENES A PUNNET SQUARE IS A TOOL USED TO PREDICT THE POSSIBLE GENOTYPES FOR THE OFFSPRING OF TWO KNOWN PARENTS. PARENT’S GENES

  15. How Does it Work?

  16. STEPS FOR MAKING CROSSES using Punnett Squares! Figure out parent alleles (genotypes) Choose Punnett size Put in parent alleles (genotypes) Fill in offspring combinations probabilities phenotypes genotypes 1. ___________ what _________________ are 2. ________correct__________ square __________ 3. ______ possible_______________________ 4. ______ boxes with _____________________ 5. Determine ____________of_____________& ____________

  17. IN PEA PLANTS T Tall is dominant over short TALL = ____ SHORT = ____ t LET’S MAKE A CROSS! PURE TALL PURE SHORT X

  18. PURE TALL parentWhat are the parent alleles? TT _________ HOMOZYGOUS   What gametes can it make? T T

  19. PURE SHORT parent What are the parent alleles? HOMOZYGOUS tt _________   What gametes can it make? t t

  20. T T t t ALL _____ of the offspring ____ % ___/4 will be Tt T t 100 4 Tt Tt Tt TALL GENOTYPE _____ PHENOTYPE _______

  21. HOW TO USE A MONOHYBRID (ONE TRAIT) PUNNETT SQUARE THE PARENTS’ ALLELES GO ON THE OUTSIDE OF THE SQUARE DROP THE LETTERS ON THE TOP, INTO EACH SQUARE B B b B b B b MOVE EACH LETTER ON THE SIDE, INTO EACH SQUARE b THE ORDER DOES NOT MATTER IN THE BOXES, BUT UPPERCASE FIRST IS A GOOD RULE B b B b

  22. HOW TO USE A MONOHYBRID (ONE TRAIT) PUNNETT SQUARE THE PARENTS’ ALLELES GO ON THE OUTSIDE OF THE SQUARE B B BB X bb b b

  23. HOW TO USE A MONOHYBRID (ONE TRAIT) PUNNETT SQUARE WHAT DO THE RESULTS SHOW? RESULTS: B B PHENOTYPIC: 100% BLACK 4:0 RATIO, BLACK TO BROWN IF B IS THE DOMINANT ALLELE FOR BLACK b Bb Bb AND b IS THE RECESSIVE ALLELE FOR BROWN GENOTYPIC: 100% Bb 4:0 ALL Bb b Bb Bb THEN WE CAN MAKE PREDICTIONS ABOUT THE OUTCOMES

  24. HOW TO USE A PUNNETT SQUARE WHAT ARE THE RESULTS? LET’S LOOK AT ANOTHER PUNNETT SQUARE AND PREDICT THE OUTCOME T t PHENOTYPIC: 75% TALL 25% SHORT 3 TO 1 RATIO: TALL TO SHORT T T T T t T IS THE DOMINANT ALLELE FOR TALLNESS GENOTYPIC: 1TT: 2Tt: 1tt 1:2:1 RATIO 25 %TT, 50% Tt, 25% tt t T t t t t IS THE RECESSIVE ALLELE FOR SHORTNESS

  25. TAKS FORMATTED ITEMS B b • 3. IF B IS THE ALLELE FOR BLACK FUR AND b IS THE ALLELE FOR WHITE FUR, WHAT PERCENT WOULD BE BLACK? • 25% • 50% • 100% • 75% B Bb BB Bb b bb • 4. WHAT FRACTION IS HOMOZYGOUS DOMINANT IN THE ABOVE CROSS? • 1/2 • 1/4 • 1/3 • 3/4

  26. TERMS TO KNOW

  27. TERMS TO KNOW

  28. Topic: Understanding Inheritance • EQ: How can inheritance be modeled?

  29. TERMS TO KNOW

  30. PRACTICAL APPLICATION OF PUNNETT SQUARES THE ALLELES OF A PARTICULAR SPECIES OF DOG CAN BE EITHER D (NORMAL HEIGHTH) OR d (DWARF). THE HETEROZYGOUS (Dd) AND HOMOZYGOUS DOMINANT (DD) FORM OF THIS DOG LOOK THE SAME (TALL). IF YOU FOUND A STRAY DOG OF THIS BREED, HOW COULD YOU DETERMINE ITS GENOTYPE?

  31. PRACTICAL APPLICATION OF PUNNETT SQUARES COULD A DOG BE CROSSED WITH ANOTHER DOG TO DETERMINE IF HE WAS PUREBRED FOR TALLNESS? WHAT GENOTYPE SHOULD THE DOG HAVE THAT IS BEING USED FOR THE CROSS?

  32. PRACTICAL APPLICATION OF PUNNETT SQUARES D D IF THE DOG IS PUREBRED (DD), IT DOESN’T MATTER WHAT YOU CROSS IT WITH, THE OFFSPRING WILL ALWAYS LOOK LIKE THE DOMINANT. DD DD D D DD DD D D D D D DD DD d Dd Dd d Dd Dd d Dd Dd

  33. PRACTICAL APPLICATION OF PUNNETT SQUARES WHAT WOULD BE THE MOST EFFECTIVE CROSS FOR DETERMINING IF THE DOG IS HETEROZYGOUS (Dd) ? CROSSING IT WITH A PUREBRED (DD) WILL NOT HELP. WHAT WOULD THE RESULTS BE IF YOU CROSSED IT WITH ANOTHER HETEROZYGOUS? WHAT WOULD THE RESULTS BE IF YOU CROSSED IT WITH A HOMOZYGOUS RECESSIVE (dd)? d D d D D d DD Dd Dd dd d d dd Dd dd Dd

  34. PRACTICAL APPLICATION OF PUNNETT SQUARES d D D d D DD Dd d Dd dd d d Dd dd dd Dd THE HETEROZYGOUS CROSS WOULD ONLY GIVE YOU A 25% CHANCE OF THE RECESSIVE TRAIT APPEARING. THE MOST EFFECTIVE CROSS WAS USING THE HOMOZYGOUS RECESSIVE. THIS WOULD GIVE A 50% CHANCE OF THE RECESSIVE TRAIT APPEARING. THIS PROCESS IS CALLED A TEST CROSS. IN A LITTER OF DOGS, IF A RECESSIVE DOG APPEARS, THEN YOU KNOW THAT THE ORIGINAL DOG WAS NOT A PUREBRED.

  35. TAKS FORMATTED ITEMS IN DROSOPHILA MELANOGASTER (FRUIT FLIES), RED EYE COLOR (R) IS DOMINANT OVER BROWN EYE COLOR (r). IF THE FLIES IN THE PICTURE WERE CROSSED, WHAT PERCENT OF THEIR OFFSPRING WOULD BE EXPECTED TO HAVE BROWN EYES? ANSWER: 50%

  36. TAKS FORMATTED ITEMS H h • WHICH OF THE FOLLOWING HAS THE hh GENOTYPE? • 1 & 3 • 2 • 4 • NONE H 1 4 3 h 2 • 2. WHICH OF THE FOLLOWING IS A TRUE STATEMENT? • INDIVIDUAL 4 IS RECESSIVE • INDIVIDUALS 1 & 3 ARE HETEROZYGOUS • INDIVIDUAL 2 IS DOMINANT • ALL INDIVIDUALS ARE FEMALE

  37. TAKS FORMATTED ITEMS B B • 5. IN THIS CROSS, WHAT IS THE RATIO OF BB TO Bb? • 3 : 1 • 4 : 1 • 2 : 2 • 0 : 4 B BB BB Bb b Bb

  38. BIBLIOGRAPHY • Mendel picture provided by wikipedia.com • Dog and tree pictures provided by Microsoft ClipArt • Graphics from TEA/ TAKS information booklet Middle School Science Grade 8 • Dice graphic from Microsoft Clipart

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