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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7 votes

Genetic linkage greater than 50 centimorgans

Just to be clear, markers on different linkage groups (chromosomes) do not recombine 50% of the time. It is just that unlinked mutations co-segregate 50% of the time. This is a direct quote from ...
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  • 3,422
6 votes
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Are there any phenotypically visible examples of gene linkage in humans?

Sex-linkage would be the canonical example. In other words, people with phenotypically male or female sex characteristics have non-random genetic predilections towards specific X-linked traits such as ...
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6 votes
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Is complete genetic linkage possible?

Complete genetic linkage does occur in some cases. Most of the Y chromosome (present as a single copy in males of many species) does not recombine with the X chromosome. Any genes in this non-...
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  • 16k
4 votes
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What exactly is a centimorgan?

I personally like to talk in Morgan (M), instead of centiMorgan (cM), because the Morgan has a more intuitive meaning than one-hundredth of its value. Morgan If two loci are at distance 1M, it means ...
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4 votes

Is complete linkage found in all four chromosomes or only Y-chromosome of Drosophila?

All chromosomes. There is no crossing over in males in Drosophila. Check out the related question Why doesn't recombination occur in male Drosophila? for sources and context.
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3 votes
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Number of homozygous recessive offspring

Taking your assumption of a cis arrangement of alleles to be true, here is how I would solve the problem. A diploid plant heterozygous for height and flower color is selfed. $TR / tr \times TR / tr$ A ...
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  • 7,729
3 votes
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How is a haploblock defined with only one SNP location?

Reading the methods In the methods, it is stated that haplotype blocks were inferred with the software Haploview: Genotype information for ESR1 and ESR2 and regions approximately 10 000 base pairs up-...
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3 votes
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Linked genes outcomes in offspring

There is nothing wrong with the question and it can be explained with not much more than mendelian genetics + linkage. What do you think are the genotypes of parents? First hint: If there is more ...
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  • 562
3 votes

Non-coding DNA correlation with rate of evolution

Whether or not species with less non-coding DNA evolve faster, the assumption that this could be explained by their genomes being more susceptible to mutation would seem to me to be based on a false ...
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2 votes

Sex linked genes?

It is not easy for an individual to figure out if it is haploid or diploid at a given sequence. To my knowledge, this is feasible only by searching for specific case of heterozygosity. The most ...
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2 votes
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Crossover Value and Genetic Mapping

As a silly example: Let's say that you are traveling along a road where you know there are bandits and thieves. You want to finish your journey quickly, and spend very little time on the road, ...
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2 votes

How to identify whether something is in linkage disequilibrium?

As per the definition you gave, you check whether there is a statistical association between the two. If knowing when allele is present at a locus does not affect the probability of finding a given ...
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2 votes

What is an intuitive explanation of linkage disequilibrium?

During sexual reproduction, the process of crossing-over means that parts of the maternal and paternal chromosomes become shuffled up with one another into chromosome 'chunks', as shown by the red and ...
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  • 2,053
1 vote
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Gametes produced after single and double cross overs

You are not taking into account that crossovers happen at the four-chromatid stage and between cromatids. Take a look at the following picture1:                 I suggest you draw down all the ...
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  • 834
1 vote

Linkage between chromosomal loci and the Hardy-Weinberg principle

Linkage is a physical reality Linkage refers to the physical presence of several loci on the same chromosome. Two loci that are said to be in close linkage mean that they are locataed relatively ...
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  • 67.6k
1 vote

Confusion about how to compute probabilities for linked genes

0.000625 looks right to me. On one chromosome, you have a 50% chance of a. Then you have a 40% chance of b (if and only if a crossover occurs). These multiply out to 20%. You multiply that by 50% ...
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  • 2,367
1 vote

Crossover Value and Genetic Mapping

There are two main question: (a) dependence of the frequency of recombination with the distance that separates genes and (b) do all crossover events take place with a single break on one chromosome? ...
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1 vote

Help with gene linkage and mapping!

I think your reasoning is sound and your ordering very likely, but I wouldn't feel comfortable with deciding the side B is on. Actually, it's more than that: I think that by using basically the same ...
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  • 321
1 vote
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Are SNPs always in linkage disequilibrium with other SNPs

Linkage disequilibrim is a result of two SNPs both appearing after a cross (e.g. in offspring). As such even at great distances two SNPs could both appear in offspring 50% of the time. Linkage ...
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  • 27.5k
1 vote

Are SNPs always in linkage disequilibrium with other SNPs

There can be a number of reasons for Linkage Disequilibriunm (LD). Here is a non-exhaustive (non-referenced also) list. Random LD happens Epistasis A recent selective sweep Hybridization Population ...
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1 vote

Linkage Disequilibrium - What does it mean when D < 0?

Consider two bi-allelic loci, A and B with alleles A1, A2 for A and B1, ...
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  • 67.6k
1 vote
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What is the exact concept of "Repulsion" and "Coupling" (Genetics)?

I guess the confusion is stemming from trying to fit the phenotypic terms coupling and repulsion to their genotypic basis. Coupling and Repulsion are both used considering the phenotypic profile of ...
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  • 4,619
1 vote
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What test to apply to detect genomic signatures of selection?

I am assuming in this answer that you do not have any information about what environment is affecting the selection pressure so that methods like Bayenv2 can't be used. The standard algorithms are: ...
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  • 67.6k
1 vote

Mitochondrial D-Loop

All the mitochondria of an individual are originating from the mother. This means that if the mother is afflicted by a mitochondrial disease, the offspring will also be affected. This is why the three ...
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  • 133
1 vote

How to decide if genes are linked in an unordered mapping problem?

I'd use a chi-squared test. You calculate what you expect to see if your hypothesis is true, and you take what you do see, and the chi-squared result tells you how likely it is that your results are ...
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