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Practice each question, then open the answer or worked solution.
Meiosis in diploid organisms results in
Ans: (d) All of the above
Explanation: Meiosis results in reduction of the number of chromosomes and gametes are formed only after meiosis. Crossing over during meiosis leads to variations. Hence, all the options are correct.
At which stage of meiosis does the genetic constitution of gametes is finally decided
Ans: (d) Anaphase I
Explanation: In anaphase I of meiosis, each homologous chromosome with its two chromatids and undivided centromere; moves towards the opposite poles of the cell. Hence , the actual reduction occurs in this stage which decides the genetic constitution of gamete.
Meiosis occurs in organisms during
Ans: (a) Sexual reproduction
Explanation: Meiosis is the reductional division that leads to production of gametes. It is not required during vegetative reproduction. Hence, option ‘a’ is the correct answer.
During anaphase-I of meiosis
Ans: (a) Homologous chromosomes separate
Explanation: Homologous chromosomes separate during Anaphase I.
Mitosis is characterised by
Ans: (b) Equal division
Explanation: There is no reduction in chromosome number during the mitosis hence it is also called an equational division that is required for growth & repairment of cells.
A bivalent of meiosis-I consists of
Ans: (c) Four chromatids and two centromere
Explanation: Bivalent is formed by pairing of two chromosomes. Thus, bivalent contains four chromatids and two centromeres.
Cells which are not dividing are likely to be at
Ans: (c) \[{G_0}\]
Explanation: Phase \[{G_0}\] is also called quiescent phase and no cell division takes place during this phase.
Which of the events listed below is not observed during mitosis?
Ans: (d) Crossing over
Explanation: Crossing over takes place only during prophase I of meiosis.It is the exchange of genetic material between homologous chromosomes that results in mixing of parental characteristics.It occurs during meiosis.
Identify the wrong statement about meiosis
Ans: (d) Two cycles of DNA replication occur
Explanation: Since the number of chromosomes in daughter cells is going to become half, there is no need for an additional cycle of DNA replication.
Select the correct statement about \[{{\mathbf{G}}_1}\] phase
Ans: (b) DNA in the cell does not replicate
Explanation: During \[{G_1}\] phase, the cell is metabolically active, continuously grows and carries out synthesis of macromolecules, but DNA synthesis does not take place during this phase.