Test 1
September, 1998

PROBLEMS

1. What was the first evidence indicating that genes are composed of DNA?

2. Why were P and S ideal radioactive tracers in the experiments performed by Hershey and Chase? Would C and H be suitable radioactive isotopes for these experiments?

3. How many different gametes are produced by a testcross where one parent is heterozygous for:

Parent
1. two gene pairs
2. four gene pairs
3. eight gene pairs
4. n gene pairs

4. Using B and b, give the likely genotype of: (see accompanying pedigree).

A. A-1
B. A-2
C. B-1
D. C-1
E. D-1
F. D-3

5. Compare meiotic anaphase I with meiotic anaphase II. Which meiotic anaphase is similar to mitotic anaphase?

6. Humans have a diploid number of 46. How many chromatids are visible at the end of mitotic prophase? How many chromosomes are moving to each pole during anaphase?

7. Explain how the phenomenon of nondisjunction acts as proof for the chromosome theory of inheritance.

8. Two-point testcrosses revealed the following map results:

pm___________ss 9 map units
pm___________bb 14 map units

A. What are the two possible maps for these loci?
B. What cross would resolve the two possible maps?

9. Smurfs are imaginary creatures who are normally blue (Bl), fuzzy (Fz), and industrious (In). Data from a three-point testcross are shown below.

Phenotype Genotype Number Progeny
ÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
normal Bl, Fz, In 324
white bl, Fz, In 49
bald Bl, fz, In 3
lazy Bl, Fz, in 42
white, bald bl, fz, In 32
white, lazy bl, Fz, in 5
bald, lazy Bl, fz, in 51
white, bald, lazy bl, fz, in 309
A. What are the parental genotypes?
B. What is the order and distance in map units between the three alleles of bl, fz, and in?

10. If the recombination frequency between two genes is 13.7%, what is the map distance between them, assuming no multiple crossovers?

11. Define the following terms:

A. First-division segregation -
B. Locus -
C. Trans-heterozygote -
D. Parental ditype -

 

12. Twenty spontaneous white-eye (w) mutants of Drosophila are examined individually to determine their reversion frequencies. Of these 12 revert spontaneously at a frequency of 10-3 to 10-5. Another 6 do not revert spontaneously at detectable frequen cy but can be induced to revert at frequencies ranging from 10-5 to 10-6 by treatment with alkylating agents. The remaining 2 cannot be made to revert under any conditions. Answer the following questions, and explain your answer.

a) Which class of mutants would you suspect to result from the insertion of transposable elements?

b) Which class of mutants are probably missense mutations?

c)Which class of mutants are probably deletions?

 

 

 

(c) Jones and Bartlett Publishers, Inc. All rights reserved.

 

 

ANSWER KEY FOR TEST - BIO50982

PROBLEMS

1. An explanation can be found on page 3 of the text.

Chapter:1 QUESTION: 5


2. Since DNA contains phosphorus but no sulfur, and proteins contain some sulfur but no phosphorus, the isotopes will specifically label only the one type of biomolecule. C and H would not have been useful since both DNA and protein contain these elements.

Chapter:1 QUESTION: 3


3. A. 4
B. 16
C. 256
D. 2n

Chapter:2 QUESTION: 15


4. A. BB
B. bb
C. Bb
D. Bb
E. bb
F. Bb
Chapter:2 QUESTION: 1


5. In anaphase I, homologous chromosomes, each composed of two chromatids joined at an undivided centromere, separate form one another and move to opposite poles. In anaphase II, the centromeres of replicated chromosomes divide longitudinally and chr omatids move to opposite poles. Anaphase II is much more like mitotic anaphase.

Chapter:3 QUESTION: 12


6. At the end of mitotic prophase 92 chromatids are visible during anaphase. 46 chromosomes are moving towards each pole.

Chapter:3 QUESTION: 10


7. Calvin Bridges demonstrated that nondisjunction events (the failure of chromosomes to separate from one another in meiosis) involving the X-chromosomes in drosophila resulted in rare exceptions to the expected pattern of inheritance. This c onclusively demonstrated that genes are contained on chromosomes since nondisjunction events precisely paralleled the exceptional inheritance of genes.

Chapter:3 QUESTION: 8


8. A. pm____9.0______ss______5.0_______bb
 bb_____14______pm_____9.0_______ss
B. Cross SsBb heterozygotes with double recessive strains. If the top map is correct, the recombination frequency between ss x bb would be 5%. If the second is correct the recombination frequency would be 23%.

Chapter:4 QUESTION: 2


9. A. The predominant genotypes are the nonrecombinant parentals, thus Bl Fz In and bl fz in.

B. bl------13.3------fz------10.1-------in

Chapter:4 QUESTION: 1


10. The distance is equal to the recombination frequency, thus the two genes lie 13.7 map units apart.

Chapter:4 QUESTION: 12


11. A. First-division segregation - Separation of a pair of alleles into different nuclei in the first meiotic division.

B. Locus - The physical position of a gene on a particular chromosome

C. Trans-heterozygote - The genetic configuration in which a heterozygous double mutant individual has received one of the mutant alleles from each parent.

D. Parental ditype - An ascus containing two pairs of nonrecombinant spores.

Chapter:4 QUESTION: 11


 

12. a) Insertions of transposable elements in eukaryotes are often characterized by genetic instability and high reversion rates. Therefore, the twelve mutants with the highest reversion frequencies are probably transposable element insertions.

b) The fact that alkylating agents can induce the second class of mutations to revert suggests that they are missense mutants. Although they do not revert spontaneously, this is probably because the exact reversal of a base substitution is an exceeding ly rare spontaneous event.

c) Deletion mutations cannot revert under any conditions because there is too much missing genetic information to be restored. Therefore, the class of mutations that does not revert probably consists of deletions. Question:

 

Chapter:*** QUESTION: 0

 

 

(c) Jones and Bartlett Publishers, Inc. All rights reserved.