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Tuesday, April 24, 2012

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  1. Tuesday, April 24, 2012 • Punnett Square checkup (end of) Block Day

  2. MendelSim Data Review Goes in entry from Friday- Entry 39: MendelSim Simulation- 4/20/12

  3. Data Table 1: Pure Red X Pure Blue Red Blue 0 50 Data Table 2: Cross of Two Red Offspring This one varied 38 12 Red Red Data Table 3: Cross of Two Blue Offspring Blue 50 Blue 0

  4. 50 (ALL) RED OFFSPRING X = PARENT 2 BLUE PARENT 1 RED = X PARENT 1 RED PARENT 2 RED 38 RED 12 BLUE = 50 (ALL) BLUE OFFSPRING X PARENT 1 BLUE PARENT 1 BLUE

  5. TAPE in these questions and answer them in your logbook • What is the trait we observed? • What are the results of crossing the red flowers with the blue flowers? • Based on the results, what do we know about the flower color gene? • What are the results for the second crossing—red crossed with red? • The flowers in the second crossing look red—but what do we know about their genetics? • What happened to the blue trait and how did it show up again in the third generation?

  6. Entry 40: Heredity and Genetics 1-4/23 See attached notes page

  7. R Chromosome structure - genes • Parts of chromosomes that code for proteins are called genes • Genes, and specifically the proteins made from them, help determine your characteristics Human chromosome # 7 • Contains about 1,800 genes • Contains over 150 million nucleotides Gene for RED flowers Link to view genes and DNA sequence

  8. Observed trait DNA mRNA protein translation transcription How does your DNA determine your traits? Example1: A person has DNA that has instructions to make LACTASE (a protein) which allows them to digest milk Example 2: The Labrador Retriever has DNA that has the instructions to make TRP-1 which converts brown pigment to black—so they have black fur.

  9. Trait – a characteristic of an organism • Example: “flower color” Gene – part of a chromosome that helps determine a specific trait • Example: “flower color gene” Allele – a form of a gene • Example: • One allele is the “blue” form of the gene • One allele is the “red” form of the gene

  10. How many chromosomes? • Humans = 23 chromosome pairs, or 46 total. We have about 24,000 genes. Some other examples: (do not need to memorize) • Pea flower = 7 chromosome pairs (14 total) • Fruit fly = 4 chromosome pairs (8 total) 13,601 genes identified so far! • Potato = 24 pairs (total 48) • Horse = 32 pairs (total 64)

  11. Chromosomes come in pairs (one from Mom and one from Dad) • This pair of chromosomes is called a “homologous pair” because they have the same genes on them - flower color gene Flower chromosome 3 (from computer simulation) From Dad From Mom

  12. IMPORTANT: homologous pairs are NOT IDENTICAL, but they have the same genes, • Alleles can be different flower color gene “Blue” allele of flower color gene “Red” allele of flower color gene From Dad From Mom

  13. The combination of alleles determines the observed characteristics RED allele BLUE allele RED allele BLUE allele BLUE allele RED allele Chromosome combination Allele combination red, red red, blue (orblue, red) blue, blue Observed characteristic RED RED BLUE

  14. Dominant and recessive alleles Only one red allele is needed for the flower to look red. • Scientists call this a DOMINANT allele Two blue alleles are needed for the flower to look blue. • Scientists call this a RECESSIVE allele

  15. Symbols used for alleles • The traditional symbols used for alleles are big and small letters • The letter chosen usually refers to the dominant allele Example: R = Red allele r = Blue allele

  16. The combination of alleles determines the observed characteristics RED allele BLUE allele RED allele BLUE allele BLUE allele RED allele Chromosome combination Allele combination red, red red, blue (orblue, red) blue, blue Observed characteristic RED RED BLUE

  17. The combination of alleles determines the observed characteristics R R R r r r Chromosome combination Allele combination RR Rr rr Observed characteristic RED RED BLUE

  18. Genotype – the two alleles that an organism has for a trait (genetics) Phenotype – the observed (or measurable) trait of an organism that relates to one gene (physical) Example: Trait = “flower color” Genotype = “RR” or “Rr” or “rr” Phenotype = “RED” or “BLUE”

  19. The combination of alleles determines the observed characteristics R R R r r r Chromosome combination GENOTYPE RR Rr rr PHENOTYPE RED RED BLUE

  20. Observed trait DNA mRNA protein translation transcription Representing genotype and phenotype based on DNA/genes

  21. BLUE PIGMENT RED PIGMENT

  22. Blue Pigment Red Pigment Functional Enzyme Y

  23. No Red Pigment for You!! Blue Pigment Red Pigment Non-Functional Enzyme Y

  24. Draw the enzymes and pigment molecules present in the cells of each type of flower below. Yes or no, is any functional enzyme Y in the cell? YES 2A Y1 GENOTYPE for flower type 1: RR Y1 1A 2B 1B nucleus PHENOTYPE of flower type 1: Allele of chromosome 2A= Y1 (functional enzyme) Allele of chromosome 2B= Y1 (functional enzyme) RED

  25. Draw the enzymes and pigment molecules present in the cells of each type of flower below. Yes or no, is any functional enzyme Y in the cell? GENOTYPE for flower type 2: Allele of chromosome 2A= Y1 (functional enzyme) Rr YES 2A Y1 2B Y2 Allele of chromosome 2B= Y2 (non-functional enzyme) 1A PHENOTYPE of flower type 2: 1B nucleus RED GENOTYPE for flower type 3: Yes or no, is any functional enzyme Y in the cell? Allele of chromosome 2A= Y2 (non-functional enzyme) 2A rr Y2 NO Y2 1A 2B 1B nucleus PHENOTYPE of flower type 3: Allele of chromosome 2B= Y2 (non-functional enzyme) BLUE

  26. ATB: NEW LOGBOOK ENTRY “HEREDITY AND GENETICS 2” • PLANNER: SHORT CHECKUP ON PUNNETT SQUARES/HEREDITY AT END OF BLOCK DAY • MAKE UP ANY MISSED WORK!

  27. Homozygous – the two alleles are the same • RR and rr are homozygous genotypes Heterozygous – the two alleles are different • Rr is a heterozygous genotype

  28. Draw the enzymes and pigment molecules present in the cells of each type of flower below. GENOTYPE for flower type 2: Allele of chromosome 2A= Y1 (functional enzyme) Allele of chromosome 2B= Y2 (non-functional enzyme) 2A 2B Y1 Y2 1A 1B WHAT DOES RrACTUALLY MEAN? nucleus R r Yes or no, is any functional enzyme Y in the cell? PHENOTYPE of flower type 2: RED YES

  29. Possible combinations of inherited chromosomes/genes Dad Mom Parents R r R r X R R Possible Offspring Order doesn’t matter, these two are the same (Rr) R r r R r r What are all possible genotypes produced from the parents? RR, Rr, rr

  30. Punnett squares organize all possible offspring combinations Dad Mom R r R r X R r R RR Rr r Rr rr

  31. R= red flower allele r= blue flower allele Genotypic ratio = 1RR: 2Rr:1rr 1 out of 4 possibilities is rr = What is probability of Rr? • How many out of 4 are red? • What is the probability of red? • What is the probability of blue? Phenotypic ratio = 3 Red:1 blue 25 % 50 % 3/4 75 % 25 %

  32. Your turn: • What are all possible genotypes and phenotypes produced by crossing Rr with rr? Complete the Punnett Square

  33. Punnett squares predict ratios of all genotypes and phenotypes produced Genotypic ratio = 2 Rr:2 rr or 1Rr : 1 rr Phenotypic ratio = 2 Red:2 Blue or1 Red : 1 Blue R= red flower allele r= blue flower allele