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, ...
- 3,313
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 ...
- 551
39
votes
Accepted
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 ...
- 68k
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 ...
- 51.5k
24
votes
Accepted
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 ...
- 17.7k
20
votes
Accepted
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 ...
- 356
20
votes
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How did Mendel know if a plant was a homozygous tall (TT), or a heterozygous tall (Tt)?
Pea plants naturally self-fertilize. So a pea plant that hasn't been manipulated will be "true breeding" that is, homozygous for the allele in question. You can therefore tell after you've ...
- 5,175
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 ...
- 9,152
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 ...
- 68k
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 ...
- 316
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 ...
- 35.3k
13
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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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 ...
- 51.5k
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 ...
- 147
11
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 ...
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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 ...
- 35.3k
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 ...
- 35.3k
9
votes
Accepted
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
Accepted
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
Accepted
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 ...
- 24.3k
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 ...
- 3,245
7
votes
Accepted
Lac operon: How can lactose enter the cell in the absence of lactose permease?
Introductory textbooks will not get into the details of the lac operon.
Basically, the operon is expressed constitutively at a low level that means that Beta Galactosidase and Lactose Permease are ...
- 4,985
7
votes
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Gene and alleles
Alleles are basically subtypes of a gene. At the time of Mendel, the molecular nature of inheritance was not known so the original definition of gene refers to "some" inheritable molecular entity ...
- 35.3k
7
votes
Accepted
Are SNPs and alleles the same thing?
Alleles are variations of a same locus that codes for a protein (gene). These alleles can come in different forms, one of which is SNP. For example, sickle cell anemia arises from an allele of the ...
- 144
7
votes
Is the genetic term "polycistronic" still used in modern biology?
Yes, it's still used.
If you search Pubmed for "polycistronic", it offers you a chart showing the counts of the term by year (top right). Downloading the CSV and making a chart shows that it's ...
- 14.2k
7
votes
How do mutations of viruses lead to drug resistance?
Summary: They Don't.
Long explanation:
Mutations happen at random. A series of factors can lead to the perceived notion that the mutation was intentional.
The mutation can be harmful, beneficial, ...
7
votes
What is the difference between non-coding and intergenic regions?
"Intergenic" is, well, an embarrassment, though it can be hard to avoid. Intergenic means, literally, between genes. Genes are, as you'd expect, genetically defined as regions of the ...
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7
votes
How are DNA virus cladograms actually calculated in practice? Is the procedure different for RNA viruses? Are these processes somewhat subjective?
Disclaimer: I'm not a bioinformatician, though I occasionally dabble in it, so I may well have some things incorrect. Please feel free to correct or make your own answer.
As I see it, you are asking ...
- 11.2k
7
votes
What is the exact definition of a "gene"?
I found a dedicated paper about the definition of what is a gene. Their short definition is:
“a gene is a discrete genomic region whose transcription is regulated
by one or more promoters and distal ...
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Only top scored, non community-wiki answers of a minimum length are eligible