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BIOLOGY 1 STANDARD 4.0 LESSON 4.7 PRINT OUT THIS LESSON BEFORE CONTINUING IN ORDER TO FOLLOW THE DIRECTIONS AND COMPLETE THE ASSIGNMENT. KEEP THESE PAGES IN YOUR NOTEBOOK Genetics and Biotechnology The student will investigate the concepts of genetics and heredity, different methods of reproduction, patterns of inheritance, and genetic disorders; as well as, explore and evaluate the DNA technologies from both a scientific and ethical perspective. Lesson 8- Examine modes of inheritance involving incomplete dominance Co-dominance and multiple alleles Interact with the Incomplete Dominance and Codominance Tutorial in Lubey's BioHELP to see how genetic problems of this nature can be solved. After going through the tutorial complete the following worksheet. Incomplete Dominance An exception to Mendel's Law of Dominance is the situation where a dominant allele does not always show its characteristic. If one were to mate a homozygous red four o'clock flower with a homozygous white four o'clock flower one would expect all the F1 offspring would be red, since red is dominant to white. The same would go for a farmer wanting to mate a red bull to a white cow. He would expect all the calves to come out red. This does not happen since the dominant allele is responsible for pigment production while the recessive white allele does not allow pigment to be produced. If we take a red four o'clock and mate it with a white one, all the offspring would be pink. Gametes -----> R R Rr Rr Rr Rr | r r The Rr genotype represents an organism containing 1/2 of the pigment needed to become red. So the individual gives off a pink color. The same thing occurs in the cattle. The recessive allele does not allow pigment to be produced. In this case the calves come out spotted. They are called roan. Pink flowers and roan cattle are hybrid and cannot breed true. Mate two pink four o'clock in the space below. Then answer the questions that follow. Parent Genotypes: _________________ X _________________ Gametes -----> R R Rr Rr Rr Rr | r r 1. What are the phenotypes of the offspring? ______________________________________________ 2. List the genotypes of the offspring. ___________________________________________________ 3. What is the genotypic ratio? _______________________________________. 4. What is another name for a heterozygous red offspring? ________________________________. Co-dominance (Courtesy: Prentice Hall Science Explorer, Cells and Heredity, 2000) For some alleles, an inheritance pattern called co-dominance exists. In codominance, the alleles are neither dominant nor recessive. As a result neither allele is masked in the offspring. In Erminette chickens, the alleles for black feathers and white feathers are co-dominant. When a chicken homozygous for black feathers is crossed with a chicken homozygous for white feathers, the heterozygous offspring will have both black and white feathers. Multiple Alleles (Courtesy: Prentice Hall Science Explorer, Cells and Heredity, 2000) Some human traits are controlled by a single gene pair that has more than two alleles. Such a gene is said to have multiple alleles - three or more forms of a gene that code for a single trait. You can think of multiple alleles as being flavors of pudding. Pudding usually comes in more flavors than just chocolate and vanilla! Even though a gene may have multiple alleles, a person can carry only two of those alleles. This is because chromosomes exist in pairs. Each chromosome in a pair carries only one allele for each gene. One human trait that is controlled by a gene with multiple alleles is blood type. Proceed to the Multiple Alleles Tutorial in Lubey's BioHELP to learn about the inheritance of human blood groups. Multiple Alleles Another exception to Mendel's laws is the presence of more than two alleles for a particular trait. One example of this is human blood type. There are four basic human blood types: A, B, AB, and O. Based on this observation one can see that A and B type blood are co-dominant and O is the recessive allele, The genotypes for these blood types are found below. Blood Type (Phenotype) A B AB O Genotypes AA and AO BB and BO AB OO Who can donate blood to whom. Blood Type A B AB O Can Receive from A and O B and O A, B, AB, and O O What will happen if a person receives the wrong blood type during transfusion? a). The protein on the red blood cell will react with the antibody in the plasma of the donor's blood. b). This reaction will cause the blood cells to join together and form clumps. c). These clumps will block small arteries and veins throughout the body, causing a heart attack, stroke, or blockage in other vital organs. 1. What blood type is considered the universal donor? __________________________. 2. What blood type is considered the universal recipient? __________________________. Genetic problems: 3. Mary has type O blood and her husband Joseph has type A blood. What are the chances of their having a child with type O blood? Joseph is heterozygous A. why must we know the genotype of Joseph? ________________________________________________________________ Work the Punnett square in the space below. 4. Mr. and Mrs. Roe had a child with type A blood. In the same hospital Mr. and Mrs. Doe had a child with type O blood. A week after they took their children home, the Roe's believed the baby they took was not theirs. They went to the hospital and had their blood types checked along with the Does. The results were as follows. Doe's Blood Types Mr. Doe : O Mrs. Doe : AB Roe's Blood Types Mr. Roe : A Mrs. Roe : O Work out he Punnett squares in the space below: Do the Roe's have the correct child? Explain _________________________________________________ Use the following link to learn about Human blood types which is an example of Co-dominance and multiple allele genetic traits Tutorial on blood type When you get to the bottom of the tutorial page click “go on” the following lessons and practice problems - Human ABO markers - blood types and genotypes - How alleles are inherited - Blood type problem set