Questions for Genetics (10 points).
1. A plant breeder has an orchid plant that is true breeding for white flowers. When she breeds her orchid with a new plant having purple flowers she finds that for the offspring, half the plants have purple flowers and half the plants have white flowers.
A. What is the genotype of the white flowered plant based on the fact that it is true breeding: homozygous or heterozygous?
B. What is a possible hypothesis for the genotype of the purpled flowered plant?
2. The same plant breeder has another species of orchid that when plants that are true breeding for red flowers are crossed with plants that are true breeding for yellow flowers, the flowers of the offspring (F1 generation) are bright orange. Assuming that the flower color is controlled by a single gene pair:
A. What can you say about the genotypes of the parent plants(i.e. are they homozygous or heterozygous)?
B. What is the genotype of the offspring?
C. If two of the orange flowered offspring are crossed, predict the ratios of the flower colors in the F2 generation.
3. Thalissemia is a rare type of anemia found mainly in populations of native or emigrated Italians. Thalissemia major is fatal in childhood, Individuals with thalissemia minor have a moderate non fatal anemia. Two parents with Thalissemia minor have three children. One died when very young of Thalissemia major and the other two show Thalissemia minor.
A. What does this suggest about the mode on inheritance for Thalissemia?
B. These parents want to have another child. What is the probability that the next child they have will not have either Thalissemia major or Thalissemia minor?
4. A mouse has the following genotype for three gene pairs: AaBbCc. List all the possible gametes the mouse can produce. Hint there are 8. Why?
5. Consider the following pedigree for a certain family. The squares represent males and the circles females. The shaded squares or circles represent individuals that exhibit a certain genetically based disorder.
A. Based on the information given, determine the mode of inheritance for the trait. Is it autosomal dominant, autosomal recessive, X linked dominant or X linked recessive?
B. Explain how you know.
C. Tell me the possible genotypes of individuals A B C and D
6. Dr. Paul's blood type is O with respect to the ABO blood system. If his mother was type B and his father is type A then explain how Dr. Paul can be type O. Show your logic with a Punett Square.
7. Faulty tooth enamel is inherited as an x linked dominant. If a male with faulty tooth enamel marries a woman with normal tooth enamel what are the expected phenotypic ratios of the offspring? Hint: remember the gene controlling this trait is on the X chromosome.
Hints: First write the genotype of the male using XF for the X chromosome carrying the allele for faulty enamel, and y for the "y" chromosome. What's the genotype of the woman?
8. In corn sugary vs. starchy kernel is controlled by two alleles S and s. SS and Ss kernels are starchy and ss kernels are sugary. Kernel color for a particular type of corn is controlled by two alleles R and r. RR individuals and Rr kernels are red and rr individuals are yellow.
Consider the cross: RRSS X rrss.
A. What is the genotype of the offspring(F1's) from this cross?
B. What is the phenotype of the offspring from this cross?
C. Suppose two F1 individuals from this cross are mated with each other. Show the expected genotypes and phenotypes for the offspring in the F2 generation.
D. A mathematical challenge. Suppose you have a kernel from the F2 generation which has the phenotype Red and Starchy. What is the probability that this Kernel is a double homozygote? (tricky) Hint: Suppose you have the cross Rr x Rr and had a RED kernel from that cross. What is the probability that the RED kernel is RR as opposed to Rr?