Sister chromatids of a pair of homologous chromosomes form tetrads, and crossing-over (exchange of genetic information between regions of non-sister chromatids in the tetrad) occurs during which phase?
a) mitotic prophase b) meiotic prophase I c) mitotic metaphase d) meiotic metaphase I e) meiotic prophase II
b) meiotic prophase I
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When transporting uncharged molecules across the membrane, which of the following is/are false?
A) Keq is always equal to one. B) ?G is not dependent upon a gradient. C) Movement requires a transport protein. D) ?G° is always equal to zero. E) both choices A and B
Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies?
A. Disruptive selection B. Stabilizing selection C. Directional selection
This organism commonly contaminates grains, corn, and peanuts and produces a potent mycotoxin called aflatoxin:
A. Pneumocystis (carinii) jiroveci B. Geotrichum candidum C. Fusarium species D. Aspergillus flavus E. Rhizopus species
Suppose you find a new triploid life form that reproduces sexually by combining the haploid gametes of three different sexes
One of the sexes is female with large and "expensive" egg cells; the other two sexes are two forms of males that each produce minute and "cheap" sperm. Using Maynard Smith's reasoning, what would be the cost of sex in this system (when the proportion of asexually producing females is low)? Fill in the table below using the following data: • n = number of asexually producing females in the population at time t • Assume that at time t, both types of males and the sexual females occur in equal proportions: Nm1 = Nm2 = Nf = N • In generation t, let k be the number of offspring produced by a female (k is the same for asexual and sexual females) • Assume that all offspring survive Adults in t genera-tion Offspring Adults in t + 1 generation Asexually repro-ducing females Sexually repro-ducing males Type 1 Sexually repro-ducing males Type 2 Sexually repro-ducing females What is the proportion of asexual females in the population at t? A. _____________________________________________________________________ What is the proportion of asexual females in the population at t + 1? B. _____________________________________________________________________ How many fold is the cost of sexual reproduction in this system? C. ________ What will be an ideal response?