Science
(a) What are chromosomes ?
(b) Explain in brief how stability of DNA content of a species is ensured in sexually reproducing organisms ?
Answer
(a) Chromosomes are thread-like structures present in the nucleus, made up of DNA and proteins. They carry genes and hence transmit genetic information from one generation to the next.
(b) In sexually reproducing organisms, meiosis produces haploid gametes with half the number of chromosomes. During fertilisation, the male and female gametes fuse to form a diploid zygote, restoring the original chromosome number. This alternate halving (meiosis) and doubling (fertilisation) ensures that the DNA content of the species remains stable from generation to generation.
Related Questions
(a) Name two metals which react violently with cold water. List any three observations which a student notes when these metal are dropped in a beaker containing water.
(b) Write a test to identify the gas evolved (if any) during the reaction of these metals with water.
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(a) How is the information communicated in "touch-me-not" plants ?
(b) What enables the plant cells to bring out the observable response ?
(c) Differentiate the movement mentioned above from the movement of tendrils in a pea plant.
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(a) at infinity and
(b) between infinity and pole P of the mirror.
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Calculate the values of the following :
(a) The total resistance of the circuit
(b) The total current drawn from the source
(c) Potential difference across the parallel combination of 10 Ω and 15 Ω resistors