Long Answer TypeState Mendel’s law of independent assortment.
(i) A homozygous tall plant (T) bearing red (R) flowers is crossed with a homozygous dwarf plant (t) bearing white flowers (r):
1) Give the genotype and phenotype of the F1 generation.
2) Give the possible combinations of the gametes which can be obtained from the F1 hybrid.
3) Give the dihybrid ratio and the phenotype of the offspring of the F2 generation when two plants of the F1 generation above are crossed.
The diagram given below represents a stage during mitotic cell division in an animal cell. 
(i) Identify the stage. Give a reason to support your answer.
(ii) Name the parts labelled 1, 2 and 3.
(iii)What is the chromosome number of the cell?
(iv)Draw a neat, labelled diagram of the cell as it would appear in the next stage. Name the stage.
Give reasons for the following:
(i) Plants begin to die when excess of soluble fertilisers are added to the soil.
(ii) Injury to the medulla oblongata results in death.
(iii)Gametes have a haploid number of chromosomes.
(iv)Green leaves are thin and broad.
(v) Lysosomes are termed suicidal bags of a cell.
(i) Excess application of soluble fertilisers makes the soil hypertonic as compared to the cell sap,so exosmosis takes place. Plants suffer water loss and plants begin to die when excess of soluble fertilisers are added to the soil due to excessive loss of water.
(ii) The medulla oblongata controls involuntary functions such as heart beat, rate of
respiration, secretion of saliva, gut peristalsis etc. Injury to the medulla oblongata
may affect important activities such as heart beat, respiration etc and may result in their stoppage and hence death.
(iii)Gametes are produced as a result of meiosis during which the chromosome number is reduced to half and each daughter cell receives half the set of chromosomes. Therefore, gametes have a haploid number of chromosomes.
(iv)Due to their broad surface areas, green leaves can absorb more sunlight at a given time, and due to the thinness of the leaves, the light energy can easily penetrate the leaf surface and be trapped by the chloroplasts. This makes photosynthesis efficient. Therefore, green leaves are thin and broad.
(v) Lysosomes contain digestive enzymes or hydrolases known as lysozymes. When the cell gets damaged or old, lysosomes burst to release lysozyme to digest their own cell. Therefore, lysosomes are termed ‘suicidal bags’ of a cell.
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