Single vs Double crossover

[Astra]

I missed a question regarding this in one of my practice exams.

I have searched for a while but cannot find a good source to learn about it.

What is the difference between the two and what do each mean?

Thank you very much!

---

Members don't see this ad.

 

[NextStepTutor_2]

I missed a question regarding this in one of my practice exams.

I have searched for a while but cannot find a good source to learn about it.

What is the difference between the two and what do each mean?

Thank you very much!

A single crossover is when homologous chromosomes are aligned and chromatids from two different chromosomes can exchange segments resulting in genetic recombination.

​

In double crossovers, chromatids from two homologous chromosomes come in contact at two points.

Another comparison is shown here

THIS is a great link that will teach you how to determine linkage distance using some simple crosses (likely to show up on the MCAT)

Hoep this helps, good luck!

 

[Astra]

A single crossover is when homologous chromosomes are aligned and chromatids from two different chromosomes can exchange segments resulting in genetic recombination.

​

In double crossovers, chromatids from two homologous chromosomes come in contact at two points.

Another comparison is shown here

View attachment 201189​

THIS is a great link that will teach you how to determine linkage distance using some simple crosses (likely to show up on the MCAT)

Hoep this helps, good luck!

I just want to personally thank you for these answers. You are truly amazing and I really appreciate it!

 

[br2pi5]

A single crossover is when homologous chromosomes are aligned and chromatids from two different chromosomes can exchange segments resulting in genetic recombination.

​

In double crossovers, chromatids from two homologous chromosomes come in contact at two points.

Another comparison is shown here

View attachment 201189​

THIS is a great link that will teach you how to determine linkage distance using some simple crosses (likely to show up on the MCAT)

Hoep this helps, good luck!

what's the difference between the "parental" and "recombinant" from single and double crossover (in the 3rd image)? why isn't there a recombinant for double crossover?

 

[NextStepTutor_1]

Hi @br2pi5,

Basically, "parental" means "original." In the third image, it looks like the double crossover they show only affected non-coding regions between the genes of interest -- you can see it on the right-hand side of the image as the blue sub-strand incorporated into the yellow strand on the top and the yellow sub-strand incorporated into the blue strand on the bottom. So this double crossover event would have been "silent" in terms of not affecting the genotype combinations, and the outcome would still have the "parental" (= "original") combination of genotypes. However, there's no reason why it would have to be that way -- the area of recombination affected by the double crossover could have also included the b/b+ coding regions.

Hope this helps clarify things!

 

[Deleted member 750603]

Geezus I don't know how I did well on this thing. Seems like I don't know anything anymore. Good luck, study hard 🙂