CELL STRUCTURES AND FUNCTION
CELL DIVISION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The number of chromatids doubled.
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The number of chromosomes doubled.
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The number of homologous chromosomes doubled.
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The amount of energy in mitochondria doubled.
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Detailed explanation-1: -During S phase, chromosomes replicate to give rise to two identical sister chromatids. These sister chromatids remain attached at their kinetochores. Hence there is no increase in number of chromosomes during S phase even though DNA replicates to increase its amount.
Detailed explanation-2: -The S phase of a cell cycle occurs during interphase, before mitosis or meiosis, and is responsible for the synthesis or replication of DNA. In this way, the genetic material of a cell is doubled before it enters mitosis or meiosis, allowing there to be enough DNA to be split into daughter cells.
Detailed explanation-3: -Then, at a critical point during interphase (called the S phase), the cell duplicates its chromosomes and ensures its systems are ready for cell division. If all conditions are ideal, the cell is now ready to move into the first phase of mitosis.
Detailed explanation-4: -During S phase, which follows G1 phase, all of the chromosomes are replicated. Following replication, each chromosome now consists of two sister chromatids (see figure below).
Detailed explanation-5: -During the S phase of the cell cycle, there is DNA replication (creating a copy of itself). The chromosome before DNA replication has one chromatin and after DNA replication has two chromatins.