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DNA – March 23, 2011 1. Name and describe one of the sex-linked diseases we discussed. 2. The eye color of a fruit fly can be red (R) or white (r). This is a sex-linked trait. – Show the cross for a white-eyed male and a heterozygous female. – What is the probability that their offspring will have red eyes? White eyes? Today’s Objective • Student will be able to… – Interpret and create pedigrees Pedigrees Ms. Klinkhachorn March 23, 2011 Biology What is a pedigree? What is a pedigree? • Visual representation of how traits are passed on from one generation to the next Why should we care about pedigrees? Why should we care about pedigrees? • To know your family history of genetic diseases/traits – Example: You can track Sickle-Cell in your family and figure out who has it Create a Key! • Examine the pedigree on the following slide. • Draw the pedigree on your paper. • Figure out what the following represent: – Circle – Square – Horizontal line DIRECTLY connecting shapes – Horizontal line indirectly connecting shapes – Long vertical line – Shaded shape Create a Key Pedigree Key Item Circle Square Horizontal Line (Direct) Horizontal Line (Indirect) Vertical Line Shaded shape Description Female Male Mating Siblings Generation Difference (Offspring) Person with the trait Design a Pedigree • Draw a pedigree for your IMMEDIATE family – Your mom and dad and siblings – Pick one characteristic HW: Design a Pedigree • Create a pedigree for a trait in your family. – Examples: Height, Hair Texture, Hair Color, Eye Color • Include (within reason) – At least 3 generations – All mating pairs and offspring – Shading to indicate who has what trait Design a Pedigree • Answer the following questions about your own pedigree: – How many males are in the family? Females? – How many members of the family have the trait your are looking for? – What is the largest family shown (2 parents + offspring)? DNA – March 24, 2011 1. What is a pedigree? Why are these useful for you to learn about? 2. In a pedigree, what do the following represent? – – – – Circle Direct Horizontal line Vertical line Shaded shape Today’s Objective • SWBAT – Interpret and create pedigrees How to Analyze a Pedigree 1. Guess – Decide if the shaded trait is dominant or recessive 2. Assign – Write out genotypes based on your guess of dominant or recessive 3. Check – Do the answers you put make sense? 4. Readjust – Only if necessary Practice Problem 1 • Draw the pedigree – There are 4 people in the family – Mom and Dad do not express the trait – They have 2 children – a boy and a girl – The girl has the trait we are studying. The boy does not Practice Problem 2 • Draw the pedigree – A couple has 3 children: a girl and 2 boys – Both parents have the trait we are studying Practice Problem 3 • Draw the following pedigree – Family of 3 people – Dad has the trait and so does his daughter DNA – March 25, 2011 1. Draw the following pedigree – – – – 6 members of the family Mom and Dad have 2 children: 1 girl and 1 boy The son is married and has a boy The daughter shows the trait and so do the wife of the son and their boy (the grandchild) 2. What trait are we studying (Dominant or Recessive)? How do you know? Justify your answer. 3. Give genotypes for each member of the family. 4. Fill out your self-eval on the back of your DNA Dominant Pedigrees • Every affected individual has at least one affected parent • Two affected individuals may have unaffected children. Recessive Pedigrees • An individual who is affected may have parents who are not affected • All the children of two affected individuals are also affected I 2 1 II 1 2 3 4 5 6 III 1 2 3 4 5 6 7 8 9 10 Sex-Linked Pedigrees • Will often see a half-shaded shape – These indicate carriers Practice Pedigree – Colorblindness • Draw the pedigree: – 3 generations, 7 total members – The grandparents have 3 children: 2 girls and a boy – The grandpa is colorblind and so is one of his daughters and his son – The son marries a girl and they have a son • Give the genotypes and then shade anybody who is a carrier in your pedigree Scenario 1 One of the bulls is sick with cow disease, which we know is a sex-linked recessive disease. This bull mates with a cow that is a carrier for the disease. 1. What are the genotypes of each of the parents? 2. Show the cross. 3. Assume that this cow couple has 4 baby cows/bulls, each with a different phenotype (as found in each of the boxes of your Punnett square). Draw this family’s pedigree. Scenario 2 A farmer wants to breed a cow and a bull in order to enter them into the “Best Looking Cow” competition at the state fair. He mates a heterozygous blue (B) bull with a yellow (Y) cow. If skin color is an incomplete dominant trait… 1. What is the bull’s genotype? What is the cow’s genotype? 2. Show the cross. 3. Give the phenotypic ratio. 4. How would this ratio change if skin color had been a codominant trait instead? Scenario 3 A different cow family is bred on the farm. The farmer knows the bull is sick, but the cow is completely healthy for this sex-linked recessive disease. 1.Show the cross. 2.Does this farmer need to worry about having sick cows? Why/Why not? Practice Drawing Pedigrees • Create a pedigree for Cystic Fibrosis, a recessive disease, based off of the following information: – Mom is heterozygous. Dad is sick. – They have three children – two girls who are carriers and one boy who is healthy. – One of the daughters marries a boy who is sick. • They have two children. The girl is sick. The boy is a carrier.