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sladkih [1.3K]
3 years ago
7

What is the topic of The Five Second Rule science experiment

Biology
1 answer:
Mademuasel [1]3 years ago
5 0
Its that food dropped on the ground is safe to eat and will not be covered in germs as long as its picked up within 5 seconds after its dropped.
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A molecule that can be used as a molecular clock has a neutral mutation rate of one mutation per 5 million years. How many years
gregori [183]

Answer:To put dates on events in evolutionary history, biologists count how many mutations have accumulated over time in a species’ genes. But these “molecular clocks” can be fickle. A paper in the 28 September Physical Review Letters mathematically relates erratic “ticking” of the clock to properties of the DNA sequence. Researchers may eventually use the results to select which genes make the best clocks.

Although mutations in DNA are rare, they are crucial for evolution. Each mutation in a gene changes one small piece of a protein molecule’s structure–sometimes rendering it non-functional and occasionally improving it. The vast majority of mutations, however, neither hurt nor help, often because they affect an unimportant part of their protein. Such a “neutral” mutation usually dies out over the generations, but occasionally one proliferates until virtually every individual has it, permanently “fixing” the mutation in the evolving species.

Over thousands of generations, these fixed mutations accumulate. To gauge the time since two species diverged from a common ancestor, biologists count the number of differences between stretches of their DNA. But different DNA segments (genes) often give different answers, and those answers differ by much more than would be expected if the average rate of mutations remained constant over evolutionary time. Sometimes they also disagree with dates inferred from fossils. Now Alpan Raval, of the Keck Graduate Institute and Claremont Graduate University, both in Claremont, California, has put precise mathematical limits on this variation.

Raval’s work is based on representing possible DNA sequences for a gene as a network of interconnected points or “nodes.” Each point represents a version of the gene sequence that differs by exactly one neutral mutation–a single DNA “letter”–from its immediate neighbors. The network contains only neutral mutations; non-functional versions of the sequence aren’t part of the network.

Models and simulations had suggested that if the number of neighbors varies from point to point–that is, if some sequences allow more neutral mutations than others–mutations accumulate erratically over time, making the molecular clock unreliable. Raval calculates precise limits on how unsteady the clock could get, based on properties of the network, such as the average number of neighbors for each node or the number of “jumps” connecting any two randomly chosen nodes. “The great strength of this paper is that it’s now mathematically worked out in much more detail than before,” says Erik van Nimwegen of the University of Basel and the Swiss Institute of Bioinformatics in Switzerland, who developed the framework that Raval uses.

Still, the relevant network properties are “not very intuitive,” van Nimwegen observes. Raval agrees. “The real question from this point on would be to identify what kinds of proteins would be good molecular clocks.” He says that according to his results, for a protein to be a good clock, “virtually all single mutations [should] be neutral”–many neighbors per node–but “as you start accumulating double and triple mutants, it should quickly become dysfunctional.” Raval is working to relate these network features to protein properties that researchers could measure in the lab.

Researchers have suggested other explanations for the erratic behavior of molecular clocks, such as variations in the mutation rate because of changes in the environment. But such environmental changes are relatively fast, so their effect should average out over evolutionary time, says David Cutler of Emory University in Atlanta. He says that in network models, by contrast, changes in the mutation rate are naturally slow because the point representing the current sequence moves slowly around the network as mutations accumulate.

Explanation:

4 0
2 years ago
Read 2 more answers
The mineral magnetite is generally black or dark gray, with a metallic luster.
SSSSS [86.1K]

Answer:

Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak.

5 0
3 years ago
All human body cells contain 46 chromosomes. However, sperm cells in men and egg cells in women have only 23 chromosomes. This i
Daniel [21]

Answer:

Two cell divisions after DNA replication

Explanation:

After the DNA is replicated, the cell undergoes two rounds of meiosis to produce 4 cells, each wIth 23 chromosomes. This is how the cell goes from a diploid to a haploid state.

5 0
3 years ago
Have you failed if your conclusion does not match your hypothesis
GaryK [48]
Absolutely not!
Your hypothesis is your educated guess on how the experiment will go. If in the end of your experiment, you find that your hypothesis was not supported, that does not make you wrong.
I hope this helps!
6 0
3 years ago
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The nucleus contains the cells genetic material in the form of A) ADP. B) ATP. C) DNA. D) RNA.
Solnce55 [7]
C. DNA is the answer
4 0
2 years ago
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