A trisomic individual is represented by (a) 2n - 1 (b) 2n - 2 - (c) 2n + 1 d) + (d) 2n + 2
Answers
(c) 2n + 1
a normal individual has 23 pairs, 46 chromosomes. In a rare genetic condition called trisomy, there are 47 chromosomes. So, if the chromosomes are XX, it may be XXX or XXY, and if the chromosomes are XY, it may be XYX or XYY. Trisomy of chromosome number 21 causes Down's Syndrome. Similarly, trisomy in 13th chromosome causes Patau's syndrome It will be represented as (2n+1)
Answer:
1. Xenia (also known as the Xenia effect) in plants is the effect of pollen on seeds and fruit of the fertilized plant. The term metaxenia was later coined and is still sometimes used to describe the effects on purely maternal tissues.
2. “B” Line
It is called as maintainer line as it is used to maintain the sterile “A” lines (Fig. 5.6). B line is isogenic to A line, in the sense, its genotype is similar to A line except for single sterility governing (ms) gene.
3. Datasseling process is being adopted in crop maize.
4. There are 6 stamens in each rice flower. Each stamen is composed of an anther and a filament.
5. Emasculation
It is done before anther dehiscence. It is generally done between 4 and 6 PM one day before anthers dehisce. It is always desirable to remove other young flowers located close to the emasculated flower to avoid confusion.
6. Hand pollination is done at anthesis by gently rubbing pollen from anthers of the staminate parent flower on the stigma of the pistillate parent flower; the pistillate flower is then covered again to prevent contamination by insects. The same procedure is valid for self-pollination.
7. Harlan also recognised smaller areas/pockets of varietal and/or racial diversity within a Vavilovian Centre, and he termed these as 'Micro centres'.
8. Disease control is achieved by use of plants that have been bred for good resistance to many diseases, and by plant cultivation approaches such as crop rotation, pathogen-free seed, appropriate planting date and plant density, control of field moisture, and pesticide use.
9. In intravarietal hybridization, the crosses are made between the plants of same variety.