Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Gene expression programming wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Microevolution wikipedia , lookup
Genome (book) wikipedia , lookup
Designer baby wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Y chromosome wikipedia , lookup
Neocentromere wikipedia , lookup
Pipe Cleaner Babies-Directions In this activity you will play the role of a parent, your lab partner will play the role of the other parent. Use chromosome and gene models to create four offspring and determine their genotypes and phenotypes. Then mathematically, you will determine the probability of having offspring with different traits. Directions You will receive a baggie with pipe cleaners and beads. The pipe cleaners represent chromosomes and the beads represent alleles located on the chromosomes. In humans, there are 23 pairs of chromosomes and 20,000 to 30,000 genes. For this exercise, we will only focus on a few. The non-sex chromosomes are called autosomes and the chromosomes that determine sex are on the sex chromosomes. The baggie contains 6 chromosomes with traits for eye color, hair color, sex and hemophilia. The hemophilia is located on the sex chromosome. Without opening the bag, notice that you have four white and two colored pipe cleaners. If you have two pink (or red) chromosomes, you are to play the role of female (XX). If you have one pink and one blue, you are to play the role of the male (XY). When you are finished put the pipe cleaners back into the baggie they came in. PROCEDURE 1. Determine the parent’s traits. Remove the chromosomes from the bag, but make sure you do NOT mix up you and your partner's chromosomes. Arrange the chromosomes in order of size, you should have two long white pipe cleaners, two shorter pipe cleaners, and the two colored pipe cleaners. KEY The white pairs represent HOMOLOGOUS CHROMOSOMES. The colored pairs represent SEX CHROMOSOMES Eye Color (longer white pipe cleaners) Brown bead represents the dominant gene - brown eyes Blue bead represents the recessive gene - blue eyes BB = brown eyes | Bb = brown eyes | bb = blue eyes Hair Color (shorter white pipe cleaners) The red bead represents the dominant gene- dark hair The ivory bead represents the recessive gene - blonde hair DD= dark hair | Dd = dark hair | dd = blonde hair Hemophilia (sex chromosomes, colored pipe cleaners) *The purple bead represents the dominant gene -- normal *The clear bead represents the recessive gene – hemophiliac *In girls: XHXH = normal | XHXh = normal (carrier) | XhXh = hemophiliac *In boys: XHY = normal | XhY = hemophiliac Time to Start Your Family Assign one person to play mom and one to play dad Step 1: Set up chromosomes. Place the chromosomes in order of picture above for both male bag and female bag Step 2: Determine Sex of baby The individual playing mom should place both pink (or red) chromosomes in separate hands behind their back. The individual playing dad should choose the left for the right hand. Lay this chromosome in the center of the table. This is the chromosome inherited from mom. The individual playing dad should place the pink (or red) and the blue chromosome in separate hands behind their back. The individual playing mom should choose a hand. Lay this chromosome in the center of the table. This chromosome is the one inherited from dad. *Use the key from page one to denote the genotype of the sex and the hemophilia status. Step 3: Determine eye color * Repeat the above steps only use the long white pipe cleaner which represents the chromosome with the alleles for eye color. *Record the genotype and phenotype for this child Step 4: Determine hair color *Repeat the above steps only use the short white pipe cleaners with represents the chromosome with the alleles for hair color. *Record the genotype and phenotype for the child Step 5: Separate the chromosomes back to their original position and repeat steps 1 through 2 until you have three children. Step 6: Record the predicted or expected results on the lower portion of the data table based on what probabilities the Punnett square shows for each trait. Pipe Cleaner Babies Analysis Name 1. What do the pipe cleaners represent? 2. What do the beads represent? 3. How many pairs of chromosomes do humans have? 4. What are autosomes? 5. What are the sex-chromosomes? 6. If you have two pink pipe cleaners which role are you playing? 7. The blue pipe cleaner represents which chromosome? 8. What do the brown beads represent? What do blue beads represent? What type of phenotype is present if you have a brown bead (B) and a blue bead (b) what genotype? Phenotypes and genotypes of Parents 1. 2. 3. 4. 5. 6. 7. What is mom’s genotype and phenotype for eye color? What is dad’s genotype and phenotype for eye color? What is mom’s genotype and phenotype for hair color? What is dad’s genotype and phenotype for hair color? What is mom’s genotype and phenotype for hemophilia? Is mom a carrier for hemophilia? What is dad’s genotype and phenotype for hemophilia? Punnett Squares genotypes Eye Color Complete the Punnett square (possibilities) for each of the following using mom and dad’s Hair Color Hemophilia Punnett Square Analysis 1. What is the phenotypic ratio for blue eyes and brown eyes from this cross? 2. What is the phenotypic ratio for dark hair and blonde hair in this cross? 3. What is the phenotypic ratio for girls for hemophilia and carriers? 4. What is the phenotypic ratio for boys for hemophilia? Can males be carriers of hemophilia? Explain. Results of Pipe Cleaner Babies Child Genotype of Sex and hemophilis Girl or boy (phenotype) Phenotype of hemophilia (use key) Genotype of Eye color Phenotype of Eye color Genotype of Hair Color Phenotype of hair color Child 1 Child 2 Child 3 Ratios: Predicted (expected) from Punnett Squares and Actual Class ratios Trait Blue Eye color Brown Eye Color Dark Hair Blonde Hair Sex Girls with hemophilia Girls – carriers Boys with hemophilia Predicted or expected Actual Class Data 1. Do the predicted/expected ratios match the actual data? Use data in your answer 2. Why would there be a difference between predicted and actual data? 3. Explain why women are carriers for the disease hemophilia. Why do their sons, but not their daughters get the disease? Explain and draw a picture of mother’s X chromosomes as a carrier and son with hemophilia. 4. Describe the difference between how normal traits are inherited and how sex-linked traits are inherited. 5. Notice on the data table that no female has the disease hemophilia. Explain why. 6. If you knew you were a carrier for hemophilia (or your wife was), would you choose to have children. Explain your reasons. If you could choose the gender of the offspring which gender would you choose and would this change your decision? Explain. 7. Other sex-linked genes found on the X chromosome include Duchenne’s muscular dystrophy (DMD), Colorblindness, male pattern baldness. Would boys or girls be expected to inherit this condition? What conditions would need to be required for a girl to be colorblind? Show the Punnett square. Pipe Cleaner Babies - Teacher's Guide Preparation Required: Create a set of baggies for the class, using pipecleaners and beads. You'll need lots of white pipe cleaners to represent the autosomes, then pink and blue to match the sex chromosomes. Bead colors can vary, though I tried to get them to match the trait. It's a little work to put together, but I use the same bags year after year. You can mix and match beads by what you can find in the store. I had trouble finding brown beads, which I would have preferred to use for the eye genes (instead of blue and grey). I store the pipe cleaners in plastic ziplock bags to be used the next year. ALTERNATIVE ON LAST PAGE TO PIPE CLEANERS Each male bag will have 1 shorter white chromosome -- ivory bead (blonde hair recessive) 1 shorter white chromosome -- red bead (dark hair dominant) 1 Long white chromosome -- blue bead (blue eye recessive) 1 Long white chromosome -- brown bead (brown eye dominant) 1 pink chromosome (pipecleaner)-purple bead (normal blood) 1 blue chromosome (pipecleaner)-no beads Genotype: Dd Bb H Dark hair, brown eyes, normal blood Each female bag will have: 1 Long white chromosome -- ivory bead (blond hair) 1 Long white chromosome -- ivory bead (blond hair) 1 shorter white chromosome -- blue bead (blue eye recessive) 1 shorter white chromosome -- brown bead (brown eye dominant) Genotype: dd Bb Hh Blond hair, brown eyes, carrier for hemophilia 1 pink chromosome -- purple bead (normal) 1 pink chromosome -- clear bead (represents a carrier for hemophilia) Sample Answers to Sections How to Use the Model (answers) 1. What do the pipe cleaners represent? _______chromosomes___________________ 2. What do the beads represent? __alleles or genes______ 3. Humans have ____23_____ pairs of chromosomes. 4. If you have two pink pipecleaners, you are playing the role of ____female__________ 5. The blue pipecleaner represents the ___Y__ chromosome. Figure out the parents traits What color eyes does the mom have __brown_ What is her genotype? Bb What color eyes does the dad have? __brown_ What is his genotype? __Bb What color hair does mom have ? blonde What is her genotype? dd What color hair does dad have? dark What is his genotype? _Dd_ Hemophilia (sex chromosomes, colored pipe cleaners) The purple bead represents the dominant gene -- normal The clear bead represents the recessive gene -- hemophiliac In girls: HH = normal | Hh = normal (carrier) | hh = hemophiliac In boys: H = normal | h = hemophiliac What is mom's genotype? __Hh_____Is she a carrier? ____yes____ What is dad's genotype? __h__ Why doesn't dad get two alleles for this trait?_Y chromosome doesn't have allele Determine the Traits of Your First Child and Data Table Each cross will be different. The first cross is just to illustrate how to do the crosses. Once students understand how to do that, the data table is easy to fill out and will go fast. You should circulate in class to help students figure out this part. Male Genotype: Dd Bb H Dark hair, brown eyes, normal blood Female Genotype: dd Bb Hh Blond hair, brown eyes, carrier for hemophilia Using punnet squares for each cross above, it should be noted that you will never see a female child with hemophilia. If this is seen, chances are, students got their bags mixed up during the crosses. This is the most common error, students will not put the proper chromosomes back to the correct parent, thus making the data inaccurate. The percentages you see (at compilation of data) should be close to: 50% dark hair, 50% blond hair 75% brown eyes, 25% blue eyes 0% hemophiliac girls 50% hemophiliac boys Watch this video of how you would sort and then choose from each set of chromosomes. You may want to demonstrate this to the class beforehand. Analysis ---On a separate page, answer the following. Write answers in complete sentence and restate the question in the answer. 1. Create a punnet square for each of the crosses, using your parents. (You'll have a square for hair color, eye color, and hemophilia) Eye color Bb x Bb, offspring will be 3/4 brown eyes, and 1/4 blue eyes Hair color Dd x dd, ofspring will be 1/2 dark hair, 1/2 blonde hair Hemophilia Hh x H Female offspring will be 1/2 normal, 1/2 carriers Male offspring will be 1/2 normal, 1/2 hemophiliacs 2. Explain why women are carrier's for the disease hemophilia. Why do their sons, but not their daughters get the disease? Females can be carriers and will donate one of the alleles for blood proteins to their sons. Males will either receive the normal allele or the abnormal (hemophilia). Females will also receive one of these alleles but will receive another X chromosome from their father which will be normal (assuming dad does not have hemophilia). 3. Describe the difference between how normal traits are inherited and how sex linked traits are inherited. Sex linked traits are inherited on the X chromosomes. Males will only receive one allele (which could be abnormal) but females will receive two alleles and have an opportunity to inherit a normal allele from their fathers. 4. The data table where all the data is combined, shows how many ACTUAL offspring would have each of the traits. The punnet squares (from #1) show the PREDICTED ratios. Compare the actual to predicted ratios for all three traits. The results will be similar but probably not exact. 5. Notice on the data table that no female has the disease hemophilia. Explain why. Females inherit a normal allele from their fathers. USE THE INFORMATION IN THE READING ON SEX-LINKED TRAITS 6. If you knew you were a carrier for hemophilia (or your wife was), would you choose to have children. Explain your reasons. Answers vary