1.Light reaction or photochemical reaction—-The assimilatory power is generated in thylakoids.
2. Dark reaction or thermochemical reaction—-Fixation of CO₂ into carbohydrated this takes place in stroma of chloroplast.
PHOTOSYNTHESIS IN HIGHER PLANTS Read More »
MEIOSIS –II is not mitosis because in meiosis-II:
•1.It occur with haploid chromosome.
•2.Two chromatids are not always similar due to crossing over. 3.Daughter cell are different from parent cell in the matter of gene recombination
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Zygotene:Pairing of homologous chromosomes takes place known as synapsis, pair of homologous chromosomes is called bivalent. Synaptonemal complex a fibrillar ladder like organelle develop between paired chromosome that stablizes pairing till crossing over takes place. The chromatids are not still visible. Pachytene: Chromatid of each synapse become visible and slightly separate, two chromatid of a chromosome are called dyad & group of 4 homologous chromosome as tetrad. Chromatids of same chromosome are called sister chromatid & chromatids of homologous chromosomes are called non sister chromatids. The exchange of segments of non sisterchromatids takes place in this stage called crossing over that produces . Breaking of segments done by enzyme endonuclease and annealing by ligase
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ALBINISM -Caused by absence of enzyme tyrosinase which convert dihydroxyphenylalanine into melanin. Only homozygous individuals are effected.
GENETIC DISEASES IN HUMAN Read More »
The chromosome appear as a long thin threads in the form of ball hence named spireme stage.
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QUIESCENT STAGE :Some cell do not enter G₁ phase after mitosis and start differentiation into specific type of cells Such cells are said to be in Quiescent stage or G₀ PHASE .These cells start division only when required.
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HETEROCHROMATIN : After cell division some chromatin fibre remain coiled & compact which stain deeply it lie close to the nuclear lamina
