2. A normal human germ cell before meiosis has how many nuclear chromosomes?

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1 1 Lesson 5 Transmission/Heredity 1. Each of the following pedigrees represent one of the major modes of inheritance that we learned about for a dominant trait: (1) Autosomal, (2) Sex linked, or (3) Maternal. For each pedigree, determine the most likely mode of inheritance. 2. A normal human germ cell before meiosis has how many nuclear chromosomes? After the first round of cell division? After the second round of cell division? 3. Two first cousins marry, and their first child has the rare autosomal recessive disease galactosemia (inability to process galactose, leading to muscle, nerve, and kidney malfunction). Assuming that the genetic disease is a result of inbreeding, indicate which members of the following pedigree MUST be heterozygous for this to be true. Explain. 4. In the same pedigree, assuming that the same first cousins have another child, what would be the probability that the new child will be affected by the same genetic disease, galactosemia? Enter your number as a fraction, decimal, or percent.

2 2 5. See the following pedigree for a rare genetic disease trait. Which of the following is the most likely mode of inheritance? Why? 1. Recessive or Dominant 2. Autosomal or Sex linked or Maternal 6. In the same pedigree, if individual A and individual B have a child, what will be the probability that the child will be affected the same genetic disease? Enter your number as a fraction, decimal, or percent. 7. Fill in the blank. An individual by a trait cannot be for the causative allele, whereas an individual by a trait must at least be for the dominant allele. [Word bank: dominant, recessive, homozygous, heterozygous, affected, unaffected] 8. A man with Kearns Sayre syndrome is affected by many muscle related deficiencies by the age of 25. At this point the man already has four children. If his syndrome follows a pattern of maternal inheritance, how many of his children would you expect to be affected by Kearns Sayre syndrome? Enter a number. 9. For a dominant trait like achondroplasia (most common cause of dwarfism), which of the following are true? Select any and all that apply. Why? A. Affected adults must carry a dominant allele B. Affected adults must carry a recessive allele C. Unaffected adults must carry a dominant allele D. Unaffected adults must carry a recessive allele

3 3 10. The accompanying pedigree is for a rare, but relatively mild, hereditary disorder of the skin. Is the disorder inherited as recessive or dominant? 11. For the same pedigree, using + to represent the dominant allele and to represent the recessive allele, give the genotype for all of the indicated individuals. You can use a / (forward slash) to separate alleles if you like. 12. Which of the following best explains the fact that a heterozygous individual affected by an autosomal dominant trait has a one half probability of passing the causative allele down to a child? Why? A. Law of segregation B. Chromosome recombination C. Inbreeding D. Mitosis 13. Duchenne muscular dystrophy is X linked and usually affects only males. Victims of the disease become progressively weaker, starting early in life. Assuming you are female, if only your father s brother had the disease, what is the probability that you have received the allele? Draw a pedigree if you need to for answering this question. Write your answer as a fraction, a decimal, or a percentage. 14. Again, assuming you are female, if only your mother s brother (that is, your maternal uncle) had Duchenne muscular dystrophy, what is the probability that you have received the allele from her? Enter your answer as a fraction, a decimal, or a percentage.

4 4 15. True or False. The law of independent assortment describes how every allele pair is divided into two separate gametes during mitosis. (Why?) 16. A man s maternal grandfather had galactosemia, a rare autosomal recessive disease caused by the inability to process galactose. The man married a woman whose sister had galactosemia. The woman is now pregnant with their first child. In the pedigree, indicate all the individuals that should be shaded to indicate their affected status. 17. Assuming these are the only affected individuals in the family, what is the probability that this couple s child will have galactosemia? Enter your answer as a fraction, a decimal, or a percentage. 18. This pedigree concerns a certain rare disease that is incapacitating but not fatal. Determine the most likely mode of inheritance. (Autosomal or Sex linked or Maternal) (dominant or recessive) Why?

5 5 19. Using + for the dominant allele and for the recessive allele, enter a possible genotype for the indicated individuals. 20. If you were this family s genetic counselor, indicate what the probability is that each couple might have an affected child. Enter your answer as an integer, fraction, decimal, or percentage. 21. Two genes (A and B) that are responsible for two very different traits can be found on the same chromosome. Based on what you know about recombination during meiosis, which one of the following depictions would most likely result in the maximum number of genotype combinations in gametes from an individual that is heterozygous for both genes? Assuming recombination occurs, what would be the maximum number of genotype combinations? Why?

6 6 22. There are four genes (W, X, Y, and Z) all located very close together on chromosome 3. They are so close together that they are considered linked and virtually no recombination can occur in between them. Assuming no recombination, if an individual is heterozygous for each gene, what is the maximum number of possible genotype combinations in the gametes after meiosis? Why? 23. Select the underlined word in the following sentence that is incorrect. Then write the correct word that should replace it. Genetic variability achieved by sex, specifically chromosome recombination and independent assortment through meiosis, is undermined by inbreeding which allows for the possibility of fewer homozygous combinations than would be expected in the general population for typically rare recessive alleles.