The Dihybrid Problem Solve

Transcription

1 DIHYBRID CROSSES (MENDELIAN) Amoeba Sisters Video Recap: Dihybrid Crosses (Mendelian Inheritance) Vocabulary practice! You probably have had enough of cats with our video. On to peas! In pea plants, yellow peas (coded for by a dominant allele Y) are dominant to green peas (requiring two recessive alleles y). Round peas (coded for by a dominant allele R) are dominant to wrinkly peas (requiring two recessive r alleles). These are actual pea plant traits, by the way! For the following, please write in the genotype or phenotype. Some are filled in for you. 7. An allele is a form of a gene. In a dihybrid cross HhSs x hhss, how many alleles does a kitten inherit from the mother? 8. How many alleles does a kitten inherit from the father?. 9. Gametes, which are sex cells, carry the alleles. Why must a gamete carry one allele (represented by a letter) from each gene? Meaning, why can t a gamete carry an hh instead of an hs or an Hh instead of a HS? The Dihybrid Problem Solve Read the beginning part about pea plants again. Bernard really likes growing peas in his garden, but the peas he likes are green. He also likes them to have a wrinkled texture, because he thinks they look much more interesting that way. Please work out a YyRr x YyRr (heterozygous cross) on the back of this sheet or on another paper while showing all work. 10. After showing your work to use as support, what is the chance that Bernard will have pea plant offspring that match the phenotype he is looking for (green, wrinkled)? 11. What is the phenotype ratio of this heterozygous cross? (yellow, round): (yellow, wrinkled): (green, round) : (green, wrinkled) 12. If Bernard did not receive any pea plants that were green and wrinkled in actuality, would you know for sure that the parent genotypes were incorrect? Why or why not?

2 SEX-LINKED TRAITS Amoeba Sisters Video Recap: Sex-Linked Traits Below is a picture of a human karyotype. 1. Place numbers by each chromosome pair. How many chromosome pairs are there? 2. How many chromosomes in total are there? 3. Circle the sex chromosomes. How many sex chromosomes are there? 4. Is this individual a male or female? 5. How were you able to determine your answer for #4? 6. Color blindness is a sex-linked recessive disorder on the X chromosome. If the allele b is used to denote color blindness, circle the genotype(s) that correctly represent(s) a female that is color blind. BB Bb bb X B X B X B Y B X B X b X b Y X b X b X b Y b X B Y 7. Color blindness is a sex-linked recessive disorder on the X chromosome. If the allele b is used to denote color blindness, circle the genotype(s) that correctly represent(s) a male that is color blind. BB Bb bb X B X B X B Y B X B X b X b Y X b X b X b Y b X B Y

3 SEX-LINKED TRAITS Sex-Linked Punnett Square Practice! 8. Bob is color blind, but he knows that neither of his parents were color blind. He is wondering if he received the gene for color blindness from his mother, his father, or both of his parents. What would you tell Bob? Show a Punnett square to prove your answer! 9. Suzy knows that an individual s sex is determined by sex chromosomes. She knows that females have two X chromosomes and males have one X and one Y chromosome. She creates the Punnett square cross below to show sex inheritance. She wants to know which parent determines the sex of a baby---is it the mother, father, or both? Complete this cross. What would you tell Suzy? Why? 10. In the video example, the sex-linked disorder was a recessive trait. However, sex-linked disorders can be dominant! (Conduct a search to see some of the sex-linked dominant disorders that exist). Sexlinked dominant disorders will show even if there is only one dominant allele present. Using the allele D to stand for a dominant sex-linked trait, show a cross with a woman who does not have a dominant sex-linked disorder (X d X d ) with a man that does. Will the disorder in this particular cross be more common in daughters or sons?

4 MULTIPLE ALLELES (BLOOD TYPES) Amoeba Sisters Video Recap: Multiple Alleles (ABO Blood Types) and Punnett Squares For the following boxes, fill in the below information regarding each blood type. Blood Type A 1. Phenotype: 2. Possible Genotype(s): 3. If the A type red blood cell below has any Blood Type B 4. Phenotype: 5. Possible Genotype(s): 6. If the B type red blood cell below has any Blood Type AB 7. Phenotype: 8. Possible Genotype(s): 9. If the AB type red blood cell below has any Blood Type O 10. Phenotype: 11. Possible Genotype(s): 12. If the O type red blood cell below has any

5 MULTIPLE ALLELES (BLOOD TYPES) Name Those Parents: Hospitals typically have excellent measures in place to prevent mix-ups, but one baby was not so lucky. The hospital has narrowed down that baby Anthony must belong to one female and one male in the below list, although the hospital also does not know which individuals are couples. Find Anthony s parents! Possible Parents: Natasha (female) Blood Type: B Adrianne (female) Blood Type: AB Rafael (male) Blood Type: O Joshua (male) Blood Type: AB Baby Anthony 13. Anthony s genotype: 14. His mother from above list (list name): 16. His father from above list (list name): 15. Her genotype: 17. His genotype: Blood Type: O 18. Draw the Punnett Square below that shows the cross between the mother and father you selected. 19. What is the percent chance in the Punnett square that you drew of having an O baby? 20. Can a baby that has blood type AB have one parent that is type O? Why or why not? If it is difficult to explain, try explaining with a Punnett Square diagram.

6 PEDIGREES Amoeba Sisters Video Recap: Pedigrees Autosomal Recessive Pedigree Directions: Consider a pedigree that is tracking an autosomal recessive trait, where two recessive alleles (tt) result in the inability to taste a chemical known as PTC. The ability to taste PTC is determined by the presence of a dominant allele (T). Complete the missing boxes in the chart. The first row has been done for you as an example! *Note: The ability to taste PTC may be more complex than a simple gene trait. Individual Phenotype Shape (in Pedigree) Shaded? Male with genotype TT PTC taster Square No Male with genotype Tt Male with genotype tt Female with genotype TT Female with genotype Tt Female with genotype tt Design an Autosomal Recessive Pedigree! A couple with the ability to taste PTC have two grown sons and one grown daughter. The sons have the ability to taste PTC. Their daughter is a PTC non-taster. She married a PTC non-taster man, and they have two sons. Draw a pedigree in the box on the right that fully represents the above scenario and tracks the inability to taste PTC (non-taster), which is caused by two recessive t alleles. In your illustrated pedigree, please make sure that: 16. (A) generations are listed as Roman numerals and the individuals are numbered. (B) the correct shapes for males and females are used. (C) the shapes that require shading are shaded. (D) the genotypes are listed next to each pedigree shape. 17. What is the phenotype of the sons in generation III? How do you know? Sex-Linked Pedigrees Sex-linked traits that are tracked in pedigrees are typically on the X chromosome. Assume the following questions refer to colorblindness, which is a sex-linked recessive trait on the X chromosome. 18. Circle the genotype(s) that represent(s) a female with the sex-linked recessive trait. X B X B X B X b X b X b X B Y X b Y 19. Circle the genotype(s) that represent(s) a male with the sex-linked recessive trait. X B X B X B X b X b X b X B Y X b Y

7 PEDIGREES 20. View the above sex-linked recessive pedigree. Can you be certain of generation I, individual #1 s genotype? Why or why not? 21. All males receive their X chromosome from their. 22. How are sex-linked pedigrees different from autosomal pedigrees? Autosomal Dominant Pedigree What about tracking an autosomal dominant trait, such as having a widow s peak? The presence of one dominant allele for this widow s peak hairline (H) will result in an individual having a widow s peak. Since this pedigree is tracking an autosomal dominant trait, shaded shapes have a widow s peak hairline. *Note: In reality, this trait may be more complex than just a simple gene. 23. How many dominant alleles does an individual need in order to have the autosomal dominant trait? 24. Is it possible to know the genotypes of the three children in generation III? Should their shapes be shaded? Explain your answer to both questions.