Chromatosomes are
a. chromosomal regions that have at least one transcriptionally active gene.
b. nucleosomes that contain linker histones.
c. fibers consisting of two coiled rows of nucleosome strings.
d. an octet of core histones.
e. strings of nucleosomes.
Ans: b
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Answer the following statements true (T) or false (F)
1. The first truly bipedal primates were the australopithecines. 2. Our species, Homo sapiens, had been in existence for only somewhat more than 50,000 years when it moved out of Africa and replaced Neanderthal Man, another species of human, about 30,000 years ago. 3. Several species of humans have occurred together in the same time and place in the past. 4. The most recent fossil and DNA evidence supports the idea that modern humans (Homo sapiens) evolved from a single stock from Africa rather than from multiple stocks in different parts of the world.
What is the normal length of a poly(A) tail?
a) about 100 adenosine residues b) about 500 adenosine residues c) about 700 adenosine residues d) about 1000 adenosine residues
All of the following are ways in which enzymes are regulated by the cell EXCEPT
A) a heavy metal (such as lead) may block the enzymes non-active site. B) by first synthesizing the enzyme in an inactive form. C) by feedback inhibition. D) a gene coding for the enzyme may be turned off.
Mothers and teachers often say they need another pair of eyes on the backs of their heads. And another pair of hands would come in handy in many situations. You can imagine that these traits would have been advantageous to our early hunter-gatherer
ancestors as well. According to sound evolutionary reasoning, what is the most likely explanation for why humans do not have these traits? A) Because they actually would not be beneficial to the fitness of individuals who possessed them. Natural selection always produces the most beneficial traits for a particular organism in a particular environment. B) Because every time they have arisen before, the individual mutants bearing these traits have been killed by chance events. Chance and natural selection interact. C) Because these variations have probably never appeared in a healthy human. As tetrapods, we are pretty much stuck with a four-limbed, two-eyed body plan; natural selection can only edit existing variations. D) Because humans are a relatively young species. If we stick around and adapt for long enough, it is inevitable that the required adaptations will arise.