For each statement below, indicate whether it is true or false, and explain why
A. To meet a challenge or develop a new function, evolution essentially builds from first principles, designing from scratch, to find the best possible solution.
B. Nearly every instance of DNA duplication leads to a new functional gene.
C. A pseudogene is very similar to a functional gene but cannot be expressed because of mutations.
D. Most genes in vertebrates are unique, and only a few genes are members of multigene families.
E. Horizontal gene transfer is very rare and thus has had little influence on the genomes of bacteria.
A. False. Evolution can work only by tinkering with the tools and materials on hand, not by starting from scratch to make completely new genes or pathways. New functions arise from the ancestral functions by a process of gradual mutational change, and thus may not represent the best possible solution to a problem.
B. False. Many duplications are subsequently lost or become pseudogenes, and only a few evolve into new genes.
C. True. Pseudogenes look very similar to normal genes but cannot produce a full-length protein, as a result of one or more disabling mutations.
D. False. A large proportion of the genes in vertebrates (and many other species) are members of multigene families.
E. False. By some estimates, 20% of the genomic DNA in some bacterial species arose by horizontal gene transfer.
You might also like to view...
Answer the question using the accompanying figure. The figure shows the alleles present at an STR locus in two
adults and four juveniles. Which of the juvenile(s) could be offspring of the adults?
a. juvenile 2 only b. juveniles 2 and 3 c. juveniles 1 and 4 d. juveniles 2 and 4 e. juveniles 1, 2, 3, and 4
Imagine you conduct a parabiosis experiment with two strains of mice, one of which lacks a functional leptin gene (ob strain) while the other lacks a functional receptor for this hormone (db strain). Which of the following outcomes would you observe?
A. no weight change in the db mouse B. decreased body weight in the db mouse C. decreased body weight in the ob mouse D. no weight change in the ob mouse E. increased body weight in the ob mouse
A simple metabolic pathway is shown below. A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?
A. an accumulation of B and no production of A and C B. an accumulation of B and C and no production of A C. an accumulation of C and no production of A and B D. an accumulation of A and B and no production of C E. an accumulation of A and no production of B and C
Why does semen contain alkaline secretions?
A. The pH of semen has no significance. B. The female vagina is acidic and thus not a favorable environment for sperm. C. Alkaline secretions are less viscous and the sperm can swim better. D. Sperm are only able to use fructose under alkaline conditions.