my question is why there is not any recombination in F1 generation?
If you took the parental chromosomes and recombined them, what would they look like?
In other words, there is recombination in the founders, but since they are homozygous (according to the figure shown), the recombination doesn't change the information content of their genomes so it doesn't "look like" any recombination happened. Physically it did, recombination is probably physically required for proper chromosome segregation during meiosis. The except is the X and Y, for which there is no recombination because they are different chromosomes. In humans however there is a bit of DNA including a handful of protein-coding genes that is shared betwenthe X and Y chromosomes, so there is recombination. I'm not sure if that happens in Drosophila, which is the example given.
In the original figure in this thread, an example was shown of fruit flies that were already highly inbred, so the father and mother were each mostly homozygous, at least on the X chromosome. In that specific example, physical recombinantions in the parental germ lines would not yield any difference in the offspring. The F1 generation however, which has one paternal and one maternal copy of each chromosome (two different X-chromosomes for F1 females), recombinations between these chromosomes in the F1 germ line will cause THEIR progeny to be different and recombinant with respect to the original two lines. This is a very specific situation, and highly inbred lines are usually only found in laboratory animals like mice, flies or fish that have been inbred for many generations by crossing brothers and sisters. Animals seem to be ok doing this, at least in the lab. The practice is not unknown even in humans (as with the ancient egyptian pharaohs who supposedly often married their sisters), although it also leads to geneticproblems in the children of such matings - not guaranteed, but more likely.
where are Gametes of F1 generation in this picture ?I am confused which picture refers to what for eg. which picture refers to Gametes of F1 generation and which picture refers to F2 generation?
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