BIOL 471

MIDTERM EXAMINATION (100 points)

(28) Indicate whether each of the following statements is true (T) or false (F):

1. T F Molecular clocks are based on changes in the sequences of DNA, which are known to occur at the same rate in all organisms and all parts of the genome.

2. T F The Neutral Theory helps to explain the observation that taxonomically diverse groups exhibit no genetic differences at the molecular level.

3. T F Fisher’s Fundamental Theorem states that the rate of change in fitness caused by selection operating on a population will be equal to the amount of variation in fitness exhibited by individuals in the population.

4. T F Punctuated equilibrium theory predicts that few intermediate forms will be seen in the fossil record because they are formed rapidly and leave few fossils.

5. T F Haplodiploidy is observed in the insect order Hymenoptera.

6. T F According to the Neutral Theory, DNA sequences in introns should be no more variable than those in exons.

7. T F Populations that undergo strict outcrossing will exhibit levels of heterozygosity greater than those expected by the Hardy-Weinberg theorem.

8. T F The Red Queen hypothesis is used to explain the observation that extinction rates in a lineage always decrease over evolutionary time.

9. T F Many parasites exhibit reduced levels of genetic recombination.

10. T F A population in Hardy-Weinberg equilibrium must have at least 50% heterozygosity.

11. T F Molecular evolution proceeds at varying rates depending on the molecule one investigates.

12. T F There are no evolutionary advantages of inbreeding, since it tends to reduce heterozygosity in populations.

13. T F The C-value of a species is an indication of the evolutionary advancement of that species.

14. T F Muller’s Ratchet helps to explain the existence of asexual species.

(18) Multiple choice. Circle only one of the choices available:

 

15. One of the assumed advantages of sex that involves purging organisms of parasites is referred to as :

1.      Heterosis

2.      Muller’s Ratchet

3.      Red Queen hypothesis

4.      Rice’s Ratchet

16. Constant rates of evolution are frequently observed:

1.      in fossil lineages

2.      in microevolution

3.      at the molecular level

4.      due to selection

17. Of the following, which is least important in explaining the sort of evolution Eldredge and Gould called punctuated equilibrium:

1.      Directional selection

2.      Genetic drift and the founder effect

3.      Bifurcation of lineages (cladogenesis)

4.      Differential extinction of species

18. Of the following, which one is not an advantage of asexual (nonrecombinational) reproduction:

1.      Mate location in widely-dispersed organisms

2.      DNA repair

3.      Maintenance of well-adapted specialized traits in parasites

4.      Reduction of the genetic "cost of meiosis"

19. Of the following, which one is likely to vary least over evolutionary time according to the Neutral Theory:

1.      Introns

2.      Exons

3.      Pseudogenes

4.      Nontranscribed spacer sequences

20. Of the following, which is not an assumption of the Hardy-Weinberg theorem:

1.      Heterozygotes have the highest fitness

2.      Mating is random

3.      Population size is infinitely large

4.      Mutation does not take place


  21.(16) Three genotypes are known for the codominant MN blood types in humans, M, MN and N. Consider the following samples from two human populations and answer the questions below.

 

 

Sample

M

MN

N

New York Caucasians

954

287

481

186

Navajo

Native Americans

361

305

52

4

   Assuming each sample is representative of each population from which it was taken, determine the following attributes of the two samples:

  1. Calculate the frequencies of each of the three genotypes in each population.
     
     
     
  2. Calculate the frequencies of the alleles M and N in each population.

 

  1. If each population is in Hardy-Weinberg equilibrium, what should the genotype frequencies be?
     
     
     
  1. Give an explanation for the differences observed for the two sets of allele and genotype frequencies.
     
     
     

22.(12) Briefly distinguish between the following pairs of alternatives, making clear how the difference is evolutionarily significant:

a. costly vs conservative sexual reproduction
 
 
 

b. apomixis vs automixis
 
 
 

c. RAPD vs RFLP
 
 
 

d. diploidy vs haplodiploidy
 
 
 
 

23.(16) Briefly define the following terms:

a. Exon shuffling
 
 
 

b. C-value paradox

 
 

c. Phyletic gradualism
 
 
 
 

d. Molecular clock
 

 

24. (10) The frequency of Tay-Sachs disease in most populations is very low, but in the Ashkenazi Jewish population prior to genetic screening, it was approximately 1 in 3600 persons. This is a lethal disease in homozygous recessive children, but is masked in heterozygotes. Calculate each of the following for such a population (assuming it is in equilibrium), and show your work:
 
 

  1. The frequency of each genotype

 

  1. What is the probability of matings between heterozygotes (hint: it is the heterozygote frequency squared)?

 

  1. The frequency of the alleles (call the Tay-Sachs recessive allele q and the normal allele p).