54 votes

How do mutations of viruses lead to drug resistance?

It doesn't. Viruses don't "know" anything. Mutations occur at random. Most of them don't do anything, or have a slight negative effect on the ability of the virus to infect and reproduce. However, ...
45 votes

Effects of mRNA vaccines on human body processes

I can address some of the points made in the post. One point about the "artificiality": I think there's one fact that's often overlooked in the discussion of mRNA vaccines. SARS‑CoV‑2, for ...
39 votes
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How does RNA transcription determine which half of the DNA to use?

I'll keep this short and simple. The direction of transcription (which determines which strand is used as the template) is controlled by the promoter, which is a region of specific DNA motifs at the 5'...
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37 votes
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Are mutations a source of genetic variation?

Going through the possible answers (A) Rates tend to be very high in most populations. This is a very unclear statement. What does "high" mean? In humans, the average mutation rate per ...
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36 votes
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Specific mechanism behind lethality of yellow coat color in mice

Really interesting question: The lethal yellow mutation (also abbreviated Ay) affects the agouti signalling protein which plays a major role in pigmentation. Heterozygous expression of it leads to the ...
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24 votes
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Is female the default sex in humans?

Summary: The idea that primary sexual determination defaults to female was proposed several decades ago and is primarily based on the observation that, in the absence of Sry, ovarian development ...
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20 votes
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Does a woman contain all the genes needed to make a man?

Human female cells contain most of the genetic information required to make a male, but they do not contain a critical component: The Y chromosome. This is a relatively small chromosome. Wikipedia ...
18 votes
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How do geneticists determine if a gene mutation is pathogenic?

The presence of a single variant relative to reference in a single patient is usually not considered adequate evidence to say that the variant causes a patient phenotype. It might be considered an ...
16 votes

Genetic linkage greater than 50 centimorgans

Understanding the statistics we use when talking about recombination rate is an important question that is unfortunately too often dismissed in an intro course to evolutionary biology or population ...
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15 votes

How does RNA transcription determine which half of the DNA to use?

To add to canadianer's answer, in fact genes can be found on both strands of the DNA in most eukaryotic cells, in the sense that the sense and anti-sense strands are not always the same strand. The ...
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13 votes

Are all carcinogens mutagens?

How can a non-mutagenic agent be carcinogenic? An agent that causes overexpression of oncogenes or inhibition of tumor suppressors, would be carcinogenic but not mutagenic. HPV, for instance, produces ...
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12 votes
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Can DNA & RNA be considered as nature's programming language?

This question can't be answered with a simple yes/no, but I would say that the analogy of DNA being the "code" used by cells is a reasonable one, if taken with a number of other considerations. DNA ...
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12 votes
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How do mutations of viruses lead to drug resistance?

This is molecular evolution and is completely undirected. Mutations happen all the time, most of them disappear without anyone noticing, since they have no evolutionary advantage to permeate. This ...
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12 votes

Are all carcinogens mutagens?

Alcohol itself is non-mutagenic because it does not directly alter DNA. (Additionally ethanol enhances carcinogenesis and is itself not a carcinogen - updated) There are similar non-mutagenic ...
12 votes

How are DNA virus cladograms actually calculated in practice? Is the procedure different for RNA viruses? Are these processes somewhat subjective?

How are DNA virus cladograms actually calculated in practice? A cladogram, or phylogenetic tree1, is constructed by comparing similarities and differences between organisms, and placing those within ...
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11 votes
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Why does Nature use a 4-level system to encode information in DNA?

The current hypothesis is that RNA came first, DNA and proteins came later. So the reason that four bases are used might be related to the initial RNA world, and then DNA just reused the already ...
10 votes
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Do nucleosomes ever completely unwrap during transcription?

Yes, nucleosomes are completely unwound. Histone chaperones such as FACT (for H2A/H2B) and ASF1, CAF-1, HIRA, Nucleophosmin etc (for H3/H4), associate with RNA Pol II and handle the displaced ...
10 votes
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Are the number of base pairs in a given chromosome same between different individuals?

Welcome to Biology.SE. if I take an X-chromosome from two random humans would I count exactly 155,270,560 base pairs in both cases No, you would probably not find the exact same number of base ...
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10 votes
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What is positive and negative supercoiling?

According to this powerpoint from the SIU School of Medicine: Right handed supercoiling = negative supercoiling (underwinding) Left handed supercoiling = positive supercoiling And from this Boston ...
10 votes

Is a gene located in the sense or the anti-sense strand?

None of the highlighted regions in your figure, is a gene. A gene is a section of DNA which gives rise to a product. Basically, a gene has an orientation (5'→ 3') i.e. it is essentially a single ...
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9 votes
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Does a man contain all the genes needed to make a woman?

This answer also involves some speculations as the question is about a good theoretical framework for a science fiction. You can find in this post about how sperm can be used to produce embryonic ...
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9 votes
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Do DNA repressors exist?

Yes, these sequences exist and they are called "silencers" (surprising, right?). There are different mechanisms by which this silencing of genes can happen. In the "classical" way the silencer is ...
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9 votes
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Do any RNAs directly inhibit transcription

Yes there are reports of RNA directly inhibiting transcription. RNA induced transcriptional silencing (RITS) is a well known pathway in Schizosaccharomyces pombe (fission yeast). Initial ...
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9 votes
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What are the potential dangers (if any) facing the twin girls recently born in China with their CCR5 gene modified?

Important notes: I am not going into the ethical aspects of editing/removing CCR5 in human embryos, neither will I discuss potential effects of introducing that mutation into the human population....
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8 votes

Does a man contain all the genes needed to make a woman?

A woman (assuming no mosaicism) has two X chromosomes in the nuclei of her cells (except for oocytes). A man, in every cell with a nucleus (except for spermatocytes), has only one, pluripotent or not. ...
8 votes
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Why do some bacteria have most genes on the leading strand of the genome?

The pattern we see in B. subtilis is quite common in prokaryotes. The origin of replication is shown at the top of the genome diagram. DNA replication proceeds bidirectionally from this point. In the ...
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8 votes
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During the process of correcting mutations via gene therapy, is the defective gene removed?

To be specific: I am talking about adult, somatic gene therapy here, and germline gene therapy experiments is still a landmine when considering ethical reasons. The defective gene codes for a ...
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8 votes
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What came first? The DNA or the DNA polymerases?

The straight forward answer is: we don't know. We don't have any direct evidence for what happened at that time nor any completely developed and coherent theories for how it worked. The widely ...
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8 votes
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How do major and minor grooves arise in the DNA helix?

First the MAJOR groove. This can be considered by forgetting that the two DNA strands are separate and thinking of them as merged together like a rope or an electric cable in my diagram below. The ...
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8 votes
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Are there knots in DNA?

I think a key factor is that DNA molecules are not passive bits of string that are left to move freely (which is what causes knots in string-like things that are left alone too long). For one thing ...
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