Some regions of chromosomes are more likely to cross over compared to others. such a region is called a "hot spot". gene a and gene b, which are in a hot spot for crossing over, are 5,000,000 bp apart on the same chromosome. gene c and gene d are also 5,000,000 bp apart but they are not in a hot spot. if you conducted two-factor crosses to compute the map distance between genes a and b and between genes c and d, would the map distances be the same between a and b compared to cand d? explain why or why not.

Explained

Explanation:

If neither of the pairs of genes was in a hot spot, the map distance would likely be the same. However, in this case it is said that although both pairs of genes are 5,000,000 bp apart, genes A and B are present in a hot spot. This means genes A and B are more likely to experience recombination and produce recombinant offspring in the F2 generation due to crossing over. As a result, the map distances for A and B will be larger than the map distances for C and D because a map unit is the number of recombinant individuals divided by the total number of individuals, which is then multiplied by 100. Since a greater percentage of individuals would be recombinant in the F2 generation, A and B will have a larger map distance.

from almost the creation of the first true maps of the earth, people started seeing how continents would be able to fit together.   in particular, people noticed that south america fits almost exactly into africa.

you should be aware that while world maps were around early in the 1600’s and better defined by the end of the 1700’s, those maps were not ‘public’ but were treated as state secrets.   and so it was not till much later that the broader ‘science’ community had access to good quality and accurate world maps.

get the whole story here…

it is now known that most of the major continental masses can be fit together in a jigsaw process.   in fact we now know that the continents were indeed once all joined together as one land mass – the supercontinent of pangaea.

if you look at most world maps you will ponder how this is evidence, as the continents really don’t appear to ‘fit’ together very well.   what you need to understand is that the vast majority of maps are drawn using a map projection that has the north and south poles (which are points) are a line the width of the map at the top and bottom.   this means that the map distorts the true shape of the earth’s land and oceans as you love closer to the poles.     some other map projections distort less, but have the map shape looking like segments of an orange.   see here for a range of map projections.   check out the way greenland changes size in each!

what is more remarkable, is the next piece of evidence when added to the shape of continents.

location of mountains and fossils

what is remarkable, when you reassemble all the continents together, the ancient mountain ranges (many now eroded to their cores) and the location of rock types and fossils all match up.

your answer should be c) enjoy!