Question

1. When during its life cycle is Sordaria diploid? When specifically does it become diploid? When does it become haploid again?

2. If it mainly exists as a haploid organism, what advantage(s) does Sordaria gain from reproducing sexually?

3. Why is Sordaria a good model organism for studying crossing over during meiosis?

Answer 1

Answer 1: After the process of fertilization(sexual reproduction) the Sordaria become diploid (2n) as it form zygote.

Specifically during the process of sexual reproduction (meiosis) when crossing over takes place.

It become haploid again as it become ascospore (8 ascosporeinside the ascus)

Explanation 1: Sordaria life cycle is dependent on the process of Alternation of Generation that is both the haploid and diploid stage in the life cycle of an organism. The Sordaria also show an important activity of crossing over which takes place during meiosis.

In fungus the multicellular phase is haploid(n) that is it has only one half the set of homologous chromosome. When two haploid cells(n cells) of different strain get together so they can perform the process of fertilization as they fuse together. By the process of fertilization the the two haploid cell will produce zygote which is diploid in nature (2n). As the zygote is the product of sexual reproduction so now after fertilization new combination of chromosome and gene is formed (crossing over) by meiosis.

Now the diploid cell goes to meiosis to produce haploid cell. Haploid cell go to mitosis process further to produce 8 individual cells called as ascospore which is haploid in nature. this ascospore is present in sac like structure called as ascus.