question_answer

Hybrid varieties of several of our food and vegetable crops are being extensively cultivated. However, plant breeders face a serious problem about their seeds. What is that and how it can be possible to solve this problem?

OR

Describe the changes in the following organs in the different phases of the menstrual cycle

(i) Ovaries

(ii) Oviducts

(iii) Uterus.

 

Answer:

Cultivation of hybrids has tremendously increased productivity. But one of the problem of hybrids is that hybrid seeds have to be produced every year by crossing the parent, genes of desired characters. If the seeds collected from hybrids are sown, the genes in the offspring will segregate and they do not maintain desired hybrid characters in the progeny. Production of hybrid seeds every year will be costly and become expensive for the farmers.

However, if these hybrids are made into apomicts (by apomixes), there is no segregation of characters in the hybrid progeny.

Then the farmers can go on using these hybrid seeds to raise new crop year after year and they do not need to buy hybrid seeds every year. Active researches are going on around the world to understand the genetics of apomixis and to transfer apomictic genes into hybrid varieties.

OR

(i)  Ovaries: During follicular phase of menstrual cycle there is growth of follicle and maturation of primary oocyte in this follicle. The mature follicle bursts to release the ovum. In luteal phase, the empty follicle forms corpus luteum which produces progesterone.

(ii) Oviducts: During ovulation the movement of fimbriae increases so as to capture the released egg. After ovulation the egg stays in fallopian tube for fertilization to takes place. In absence of fertilization the egg degenerates leaving no residue.

(iii) Uterus: During follicular phase of menstrual cycle, there is proliferation of the epithelial lining (endometrium) of uterus and of ruptured blood vessels. In secretory phase, there is mther thickening of endometrium. The uterine glands secrete a nutrient fluid and blood vessels become long and coiled. In menstrual phase, the endometrium breaks down causing bleeding or menstruation.