You are interested in expression of regions of the X chromosome at different times in human fetal development. You hypothesize that large regions of the X chromosomes will be expressed at times when parts of the reproductive organs are developing
What structural and chemical characteristics of the X chromosome might you look at over time to determine when expression of genes on the X chromosome is enhanced or repressed?
What will be an ideal response?
Answer: Answers will vary, but should include examining the X chromosome for the presence or amount of euchromatin versus heterochromatin by staining, electron microscopy, or nuclease digestion. Chemically, the relative amount of methylation or acetylation of histones within regions of the X chromosomes could also be examined over time. More euchromatin and acetylation would indicate more "open" or actively expressed DNA; heterochromatin and increased amounts of methylation of histones and DNA would indicate "closed" chromatin or gene silencing.
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A. NADH B. hydrogen ions C. phosphate D. ATP E. oxygen
The partial pressure of atmospheric oxygen gas at sea
level is about a. 0.3 mm Hg. b. 160 mm Hg. c. 300 mm Hg. d. 592 mm Hg. e. 745 mm Hg.
The legless condition that is observed in several groups of extant reptiles is the result of _____
A) their common ancestor having been legless B) a shared adaptation to an arboreal (living in trees) lifestyle C) several instances of the legless condition arising independently of each other D) individual lizards adapting to a fossorial (living in burrows) lifestyle during their lifetimes
Chromosome number reduces during
A. mitosis. B. interphase. C. meiosis I. D. meiosis II.