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

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Presentation on theme: "Tuesday, April 24, 2012 -Punnett Square checkup (end of) Block Day."— Presentation transcript:

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

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

3 Parent 1Parent 2Offspring (after 50 crosses) RedBlue Data Table 1: Pure Red X Pure Blue Parent 1Parent 2Offspring (after 50 crosses) RedBlue Data Table 2: Cross of Two Red Offspring Data Table 3: Cross of Two Blue Offspring Parent 1Parent 2Offspring (after 50 crosses) RedBlue Red Blue Red Blue This one varied 0 50

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

5 TAPE in these questions and answer them in your logbook 1.What is the trait we observed? 2.What are the results of crossing the red flowers with the blue flowers? 3.Based on the results, what do we know about the flower color gene? 4.What are the results for the second crossing—red crossed with red? 5.The flowers in the second crossing look red— but what do we know about their genetics? 6.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 Chromosome structure - genes Human chromosome # 7 Contains about 1,800 genes Contains over 150 million nucleotides Link to view genes and DNA sequence Parts of chromosomes that code for proteins are called genes Genes, and specifically the proteins made from them, help determine your characteristics R Gene for RED flowers

8 How does your DNA determine your traits? DNAmRNAprotein Observed trait transcription translation 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 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) How many chromosomes?

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 chromosome 3 (from computer simulation) From Dad From Mom flower color gene

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

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

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

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 Chromosome combination GENOTYPE PHENOTYPE RR Rr rr RED BLUE RRrrr

20 Representing genotype and phenotype based on DNA/genes DNAmRNAprotein Observed trait transcription translation

21 BLUE PIGMENT RED PIGMENT

22 Blue Pigment Functional Enzyme Y Red Pigment

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

24 GENOTYPE for flower type 1: Allele of chromosome 2A= Y1 (functional enzyme) PHENOTYPE of flower type 1: nucleus Y1 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? Allele of chromosome 2B= Y1 (functional enzyme ) 2A 2B 1B 1A YES RED RR

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

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 ) PHENOTYPE of flower type 2 : nucleus Y1 Y2 Yes or no, is any functional enzyme Y in the cell? Allele of chromosome 2B= Y2 (non-functional enzyme ) 2A 2B 1B 1A YES RED WHAT DOES Rr ACTUALLY MEAN? Rr

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

30 Punnett squares organize all possible offspring combinations R r X Rr R r RR Rrrr Rr DadMom

31 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? Rr RRRRr r rr Genotypic ratio= 1RR: 2Rr:1rr 25 % 50 % 3/4 75 % 25 % R= red flower allele r= blue flower allele Phenotypic ratio=3 Red:1 blue

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

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 or 1 Red : 1 Blue rr RRr rrr R= red flower allele r= blue flower allele


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