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14 votes

Can a blood type O be born from AB and A parents?

The ABO blood type is controlled by a single gene (the ABO gene) with three types of alleles inferred from classical genetics: i, IA, and IB. The IA allele gives type A, IB gives type B, and i gives ...
KaPy3141's user avatar
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13 votes
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Do some genes follow Rock-Paper-Scissors model of dominance?

A quick search gives this same question in this Reddit post. Apparently, there is not yet an existing example of such dominance of three alleles on one another. That said, if you're interested in ...
allepasse's user avatar
  • 341
12 votes
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Are alleles equally sized?

In general, alleles don't have to be the same size. Two major examples which come to mind are the Huntingtin gene and FMR1. Huntingtin is the causative gene of Huntington's disease. In people with ...
R.M.'s user avatar
  • 1,554
8 votes

Have there ever been "half-twins" who were halfway between siblings and twins?

Yes. A case of semi-identical twins was reported in 2006. These twins share 100% of their maternal alleles and 50% for their paternal alleles. It's hypothesized this arose from a double fertilization ...
Darlingtonia's user avatar
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6 votes

What are multiallelic genes?

More than two alternative forms (alleles)of a gene in a population occupying the same locus on a chromosome or its homologue is known as multiple alleles. Multiple alleles arise due to mutations of ...
Mesentery's user avatar
  • 3,283
6 votes
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What is meant by 'identical alleles'?

These are just issues with singular and plural and whether you refer to individual copies or categories/types. Two of the same allele copies are the same allele (category/type). Two different alleles (...
Bryan Krause's user avatar
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5 votes

How does sexual reproduction generate more genetic variation?

Short answer it doesn't. Sexual reproduction generates new combinations of traits and increases the difference between individuals in the same populations. New combinations means beneficial traits ...
John's user avatar
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5 votes
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How allele is related to trait that is more complex than two cases (ex. height)?

You are absolutely correct that many traits are not "digital", but "analog". In genetics, these are usually called quantitative traits. Such traits generally do not follow Mendel's laws of inheritance,...
Roland's user avatar
  • 5,705
5 votes

Genetic mutations and new alleles

So the term allele is a broad one, and simply refers to the different versions of any piece of DNA in circulation in the gene pool - it doesn't need to refer to a gene. I can talk about the alleles at ...
Dermot Harnett's user avatar
5 votes
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Question regarding the number of alleles

The two-allele scenario is often used in genetics teaching because of its simplicity. However, quite a few genes have more than two alleles. Some examples that readily come to mind are: The ABO gene ...
Adhish's user avatar
  • 1,307
5 votes
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Red and White Flower or purely Pink? Phenotype of a Flower Species with a Co-dominant Trait

Unfortunately, that nomenclature is kind of old-fashioned; it predates our understanding of what's going on at a molecular level. Don't get hung up on the language. Lots and lots of genes and ...
swbarnes2's user avatar
  • 5,230
5 votes
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Genotype vs Alleles - What's the difference?

Please note that opinions on the exact wording of the following can differ a lot. You will have to find one for yourself that works best for you. Gene = An element within the DNA/Genome with function(...
markur's user avatar
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4 votes
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Is the term 'allele' specific to sexual populations?

No, it's fine to use for asexuals too. There's an ambiguity in the term "locus" for asexuals, but "allele" is fine, and "gene" is not much more ambiguous than it is for sexuals (which isn't saying ...
Daniel Weissman's user avatar
4 votes

How does sexual reproduction generate more genetic variation?

There are two questions here. 1) What is genetic variance? It is actually clearly defined. 2) How does sexual reproduction generate more genetic variation? What is genetic variance? Assuming bi-...
Remi.b's user avatar
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4 votes
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Considering Two Genes, Are There Only Two Possible Outcomes for the Four Gametes Produced After Meiosis, Regardless of Independent Assortment?

A "single meiotic event" would include both meiosis I and meiosis II. So, if you start with an AaBb mother cell prior to any phase of meiosis, then observe one of the resulting final ...
Darlingtonia's user avatar
  • 2,582
4 votes

Can a deletion occur on only one strand of a human chromosome?

This is a somewhat semantic question. In terms of WHEN a deletion happens, I think it's commonly on only one strand as most mutations are caused by a collision from radiation or sometimes a chemical. ...
shigeta's user avatar
  • 28.2k
4 votes

Can a deletion occur on only one strand of a human chromosome?

As it appears that most deletions occur by mechanisms that do not involve large-scale strand separation (e.g. during crossing over or by translocation etc.) this is unlikely to happen (see e.g. ...
David's user avatar
  • 25.8k
4 votes

Have there ever been "half-twins" who were halfway between siblings and twins?

Though your question doesn't make sense to me, I believe the answer is Yes. See the following paper about "sesquizygotic" twins: Gabbett, M.T., Laporte, J., Sekar, R., et al. 2019. Molecular ...
theforestecologist's user avatar
3 votes

how can a recessive allele become represented in a significant number of individuals in a population

A recessive allele is one whose phenotype can be masked by a dominant allele. A recessive allele is not necessarily deleterious, and the dominant allele does not necessarily have higher fitness than ...
Nathan's user avatar
  • 166
3 votes
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Dominance coefficient

Thank you for asking such a well-thought out question, I really enjoyed how hard this made me think about the concept. I think there might be an issue here that's quite common to biology, in my ...
lmrta's user avatar
  • 146
3 votes

How does allele dominance work in polyploid organisms?

Dominance works in the same way. However, polyploids have complex inheritance patterns! 1. Punnett square for polyploid inheritance One might assume that you would need a four-dimensional table ...
Macrophage's user avatar
3 votes
Accepted

Is protein production doubled if you have homozygous dominant genes as opposed to heterozygous genes?

Dominance is defined based on the phenotype Dominance is defined based on a phenotype of interest. Pick a phenotype, say coat color for example. If genotypes AA ...
Remi.b's user avatar
  • 68.1k
3 votes

What is a gene transcript, how is it different from an allele?

No. A gene is a unit of the genome stored in the form of DNA. It can be transcribed into mRNA (the transcript) to be used as a template in protein synthesis. A gene can come in many different ...
Bob's user avatar
  • 556
3 votes

Is there a practical upper limit to ploidy?

Note that it is customary to restrict posts to a single question, which is easier to answer for these complex topics. I'll do what I can here. I'm going to deal with everything at once and then ...
Maximilian Press's user avatar
3 votes

What is an allele?

The question takes one sentence in the Nature Scitable article about alleles out of context. The statement: “Humans are called diploid organisms because they have two alleles one from each parent....
David's user avatar
  • 25.8k
3 votes
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Get "DNA" of one parent based on its children

Ok, I think I can answer somewhat usefully with the update. It's helpful in this case to think in terms of sampling alleles. It's true that the cases that you give are not 100% unambiguous, but it is ...
Maximilian Press's user avatar
3 votes
Accepted

Can gene mutations cause Down's syndrome in humans?

Don't feel bad, that question is horribly worded. Gene mutation is a confusing choice of words, it is not a specific thing. First, down syndrome IS caused by a mutation, specifically a duplication. ...
John's user avatar
  • 14.7k
3 votes

Genotype vs Alleles - What's the difference?

An allele is a variant of a gene, while a genotype is an (arbitrarily) specified combination of alleles, mostly stating the homo- or heterocygous presence or absence of certain mutation(s) in a ...
KaPy3141's user avatar
  • 1,597
3 votes

What really is an allele?

That's a poor definition of allele. Alleles don't need to have anything to do with traits - different alleles can code for the same or different traits. Alleles are simply different versions of a ...
user438383's user avatar
  • 2,351
2 votes

Chance of child inheriting at least one copy of an allele - heterozygote mother, unknown father

It seems that what you are trying to do is calculate the probability of the child having at least one copy of the "risk allele" which I will denote as "A" (and it's counterpart "a"). First of all you ...
rg255's user avatar
  • 16.1k

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