PRACTICE PROBLEMS
1. Briefly define Mendel's law of segregation and law of independent assortment.
2. The ability to taste PTC is inherited as a dominant trait. A male taster, whose father is a non-taster, marries a female non-taster. What are the phenotypes of their children?
3. Can the following matings produce the child shown? Use your knowledge of the ABO blood types to answer this question.
Mating (female x male) Child
a) Type A x Type A Type O
b) Type AB x Type A Type O
c) Type B x Type B Type A
d) Type B x Type AB Type A
e) Type O x Type O Type B
4. Let us assume rat eye color is controlled by one gene and is inherited as a Mendelian trait. The dominant allele is red and the recessive allele is black. You are given a red-eyed rat and are asked to determine the genotype. How would you do this? Show all possibilities for the possible genotypes.
5. A true breeding tall plant (dominant) was crossed with a true breeding dwarf plant.
What is the outcome of the F1 generation?
What is the outcome of the F2 generation?
State the genotypic and phenotypic ratios for each generation.
6. Red flowering snapdragons are homozygous for the allele R’. White flowering snapdragons are homozygous for the allele R. A white flowering snapdragon was crossed with a red flowering snapdragon. Identify the outcome of the F1 generation. Give the genotypic and phenotypic ratios as well. (incomplete dominance)
7. A plant has an allele for color we will name 'A.' 'A' is dominant and codes for green. The recessive allele 'a' codes for blue. The plant also has an allele for height we will name 'B'. 'B' codes for tall plants and 'b' codes for short plants. Give the genotypes and phenotypes of the following matings.
a) AABB x aabb
b) AaBB x aabb
c) AaBb x AaBb
d) AaBb x aabb
8. A brown mouse is repeatedly mated with a white mouse. All of their offspring are brown. What are the parents’ genotypes? What type of inheritance is this? If two of the brown mice of the F1 generation were mated, what would be the outcome?
9. If you were given one of the brown mice from problem 8, how would you determine the genotype of the mouse? Show your work.
10. In a cross between a white-eyed female fruit fly and a red-eyed male fruit fly, what percent of the female offspring will have red eyes? (white eyes are X-linked, recessive)
11. Let us assume there is a gene that codes for berry color. The dominant allele is red and the recessive allele is purple. Let us also assume there is a gene that codes for berry size. The dominant allele is large size and the recessive allele is small size. If a berry plant whose berries are small and heterozygous red cross-fertilizes with a berry plant whose berries are heterozygous large and red, what are the genotypic and phenotypic ratios of the F1 generation?
12. A red-eyed mouse was mated with a white-eyed mouse. All of the offspring were red-eyed. Demonstrate this cross. Then perform an F1 cross. What are the genotypic and phenotypic ratios of the F1 cross?
13. A blue flowering plant was crossed with a white flowering plant. All of the offspring were pale blue. What type of inheritance is this? Demonstrate this cross. Perform an F1 cross, giving the genotypic and phenotypic ratios.
14. A common form of red-green color blindness in humans is caused by the presence of an X-linked recessive allele. Given simply that, please answer the following:
A. Can two color-blind parents give birth to a normal son or daughter?
B. Can two normal parents produce a color-blind daughter?
C. Can two normal parents produce a color-blind son?
15. A strange woman has a bizzare condition known as "Cyclops" syndrome, where she has a single eye in the middle of her forehead. The allele for the normal condition (i.e. NO "Cyclops" syndrome) is recessive (cc). Her father is a Cyclops, as well as her mother. Her father's mother was normal. What is the genotype of the strange woman's father?
16. In the ABO blood system in human beings, alleles A and B are codominant and both are dominant to the O allele. In a paternity dispute, a type AB woman claimed that one of four men was the father of her type A child (the child would be type A with a genotype of either be AA or AO). Which of the following men could be the father of the child on the basis of the evidence given?
a. The Type A father?
b. The Type B father?
c. The Type O father?
d. The Type AB father?
17. A plant has the genotype AArrSs. Cross out gene combinations that cannot be produced or are not normal in the haploid gametes of this plant:
AasArSArsarSaRsArrASAarrSs
18. Genes often interact with one another. The term epistasis is applied to cases in which one gene alters the expression of another gene that is independently inherited. In Labrador retriever dogs one gene locus is involved with production of melanin pigment: B (black) and b (brown) are its two alleles. Another gene locus determines whether the melanin produced is actually deposited in individual hairs as they grow (E) or not deposited (e). Any dog with at least one dominant allele B and one dominant allele E will be a black Labrador. A dog with the homozygous recessive bb and at least one dominant E will be a lighter, chocolate Labrador. If a dog has the homozygous ee genotype it will be a yellow Labrador, regardless of the alleles at the pigment locus.
a. Give possible genotypes for a dog with the black Labrador phenotype?
With respect to locus B
With respect to locus E
b. Give possible genotypes for a dog with the chocolate Labrador phenotype?
With respect to locus B
With respect to locus E
c. Give possible genotypes for a dog with the yellow Labrador phenotype?
With respect to locus B
With respect to locus E
d. A yellow Labrador with the genotype bbee mates with a black Labrador that is homozygous for both alleles. What are the ratios of genotypes and phenotypes expected in the F1 and F2 generations?
Thought Question
There are no definitive "right" results to this question. You will have to use reasoning to come up with ways that you would solve this problem.
19. You have identified a new gene in mice. This gene codes for fur color. One allele specifies white fur color while the other allele specifies brown fur color. Determine whether the relationship between the two alleles is one of complete dominance or incomplete dominance. Devise genetic crosses to determine the pattern of inheritance. On what observations would you make your conclusions?
20. Name the nucleotides found in the following nucleic acids:
a) DNA b) RNA
______
______
______
______
21. Name the purines and pyrimidines.
22. List the enzymes involved in replication and their functions.
23. Given the following nucleotide sequence of this template DNA strand, transcribe and translate the sequence into a protein.
3' 5'
T / A / C / A / A / T / G / C / A / C / G / G / G / T / T / C / T / G / A / C / TmRNA
5' 3'
Protein Sequence
______
______
24. Name the 3 types of RNA, giving the function of each.
25. Where do the following take place or exist in the cell?
a) transcription-
b) translation-
c) DNA replication-
d) tRNA synthesis-