Self pollination & Cross pollination

[chound]

My book says self pollination maintains the parental characters or purity of the race indefinitely and is used to maintain pure lines for hybridization experiments.

How can that be true. Coz, meiosis takes place in micro & mega spore mother cells. So there is crossing over which will lead to variation right?

 

[Moonbear]

Self-pollination reduces variation, but does not entirely eliminate it (due to crossing over and segregation of chromosomes during meiosis, as you have indicated), unless the parent is already homozygous for a trait. If one is only interested in studying limited traits, then it's possible to breed plants that are homozygous and then preserve those homozygous traits through continual inbreeding (self-pollination).

 

[ravenprp]

While it is true that meiosis and crossing over can lead to genetic variation, self pollination can still maintain the parental characters or purity of the race indefinitely. This is because self pollination involves the transfer of pollen from the anther of a flower to the stigma of the same flower or a flower on the same plant. In this process, there is no opportunity for genetic material from another plant to be introduced, so the offspring will have the same genetic makeup as the parent plant.

Cross pollination, on the other hand, involves the transfer of pollen from one plant to the stigma of another plant. This can lead to genetic variation as the genetic material from two different plants combines, resulting in new traits in the offspring. However, this does not mean that self pollination is not important in maintaining pure lines for hybridization experiments. In fact, self pollination is often used in conjunction with cross pollination to create pure lines for hybridization experiments.

Additionally, while crossing over during meiosis can lead to genetic variation, it is not a guarantee. Some organisms have mechanisms in place to prevent or limit crossing over, such as gene suppression or physical barriers between homologous chromosomes. Furthermore, even if crossing over does occur, it does not necessarily mean that the offspring will have vastly different traits from the parent plant. In self pollination, the genetic material is identical, so there is a higher likelihood of maintaining the desired traits in the offspring.

In summary, while self pollination may not completely eliminate the possibility of genetic variation, it is a useful method for maintaining purity in plants for hybridization experiments. It is often used in conjunction with cross pollination to create pure lines with desired traits for breeding purposes.