Genetics Sample Test

1. The situation in which an expected phenotype is not expressed is referred to as

    A) Pleiotropy

    B) Variable expressivity

    C) Incomplete penetrance

    D) Recessivity

2. The longitudinal halves of a chromosome that has undergone replication are known as

    A) Centrosomes

    B) Chromatids

    C) Chaismata

    D) Centromeres

3. A person of blood type AB can receive blood from a person of

    A) Any other ABO type

    B) Only AB

    C) Only O

    D) Either A or B

4. An RNA molecule folds back upon itself to form a "hairpin" structure held together by a region of base pairing. One segment of the molecule in the paired region has the base sequence 5'-GCAUUGA-3'. What is the base sequence with which this segment is paired?

    A) 5'-UCAAUGC-3'

    B) 5'-GCAUUGA-3'

    C) 5'-TCAATGC-3'   

    D) 5'-GCATTGA-3'

5. A dihybrid cross SS tt x ss TT is made in which S is dominant, but there is no dominance between T and t. Assuming independent assortment, how many phenotypic classes are expected in F2?

    A) 2

    B) 3

    C) 4

    D) 5

    E) 6

6. A DNA strand consists of any sequence of four kinds of nucleotides. Suppose there were only 16 different amino acids instead of 20. Which of the following statements would be correct descriptions of the minimal number of nucleotides necessary to create a genetic code

A) 1

    B) 2, provided that chain termination does not require a special codon

    C) 3, provided that chain termination does require a special codon

    D) 2, no matter how chain termination is accomplished

    E) Both B and C

7. Assuming equal sex ratios, if a mating has already produced 3 girls, what is the probability that the next child will be a girl?

    A) 0

    B) 1

    C) 1/2

    D) (1/2)3

    E) 1 – (1/2)3

8. The sequence of the transcript is 5'-GGUUACAUUC-3'. The sequence of the DNA template would be

    A) 5'-GGUUACAUUC-3'

    B) 5'-GAATGTAACC-3'

    C) 5'-CCAATGTAAG-3'

    D) 5'-CUUACAUUGG-3'

9. R type strain of S. pneumoniae does not cause pneumonia because bacterial cells

    A) Are surrounded by a polysaccharide capsule

    B) Are unable to synthesize a polysaccharide capsule

    C) Are undetectable by the immune system

    D) Are unable to form colonies

10. Parents heterozygous for a recessive allele are called

    A) Carriers

    B) Codominant

    C) Hybrids

    D) True-breeding

    E) Pleiotropic

11. Probabilities are calculated using the addition rule when they

    A) Are equally likely

    B) Are independent

    C) Are mutually exclusive

    D) Occur disproportionately

12. If a F1 plant that is heterozygous for 5 independently assorting genes is selfed (crossed with itself), how many unique genotypes are possible in the F2?

    A) 32

    B)125

    C) 243

    D) 1,024

13. Two parents with blood types A and O have a child who has type O blood. What is the chance that their next child will be type A? 

    A) 0

    B) 1/2

    C) 1/4

    D) 1

14. What sort of ratio of phenotypes would you expect with epistasis? 

    A) 9:3:3:1

    B) 3:1

    C) 1:1

    D) 15:1

15. If a DNA strand has 10% cytosine, what percent of its bases are thymine? 

    A) 10%

    B) 20%

    C) 30%

    D) 40%

Short answer (2 points each):

    16. Pangenesis

    17. True Breeding

    18. Phenylalanine Hydroxylase

    19. Archae

    20. Pleiotrophy

Discussion (12 points each)

21. Study the following pedigree and answer these questions,

    a. What is the mechanism of inheritance for this trait?

    b. What does the double line mean in the pedigree mean?

    c. What is the genotype of the parents in generation I ?

    d. What is the probability that the offsping of a mating between III-4 and IV-3 will express the trait?

22. Several crosses of long-haired rabbits were made. The rabbits differed in fur color and texture. For each cross listed, what are the most likely genotypes of the parents?

Parents                                                                 Progeny

Male,                                             Female black, straight black, curled gray, straight, gray, curled

a. black     x         gray                           120                 0                    0                            0

straight                curled

_________        _________

b. black     x         black                           90                  0                   30                           0

  straight              curled

_________       __________

c. black      x        gray                            50                   0                    50                            0

   curled               straight

_________     ___________

23. In maize (corn), a dominant allele A is necessary of yellow seed color, as opposed to colorless (a). Another gene has a recessive allele (e) that results in waxy starch, as opposed to normal starch (E). The two genes segregate independently. Give the phenotypes and relative frequencies for offspring resulting when a plant of genetic constitution AaEE is test crossed, be sure to show your work.

24. Discuss the concept of complementation in genetics. Include examples of the genotype and phenotype of a cross that does and does not complement. How do you analyze a complement screen, give an example.

Extra Credit: Compare and contrast mitosis and meiosis