In a sexually reproducing organism, which one of the following statements is appropriate both for the parent and offspring?

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  1. Chromosome number increases but DNA content remains constant
  2. Both chromosome number and DNA content remains constant
  3. Chromosome number decreases but DNA content remains constant
  4. Both chromosome number and DNA content decreases

Answer (Detailed Solution Below)

Option 2 : Both chromosome number and DNA content remains constant
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The correct answer is Both chromosome number and DNA content remain constant.

Key Points

  • During sexual reproduction, gametes (sperm and egg cells) are produced through a process called meiosis.
  • Meiosis involves a reduction in chromosome number, but each chromosome still contains the same amount of DNA.
  • When these gametes fuse during fertilization, the diploid chromosome number is restored in the zygote.
  • Therefore, both the chromosome number and DNA content remain constant when considering the parent and offspring in sexually reproducing organisms

Additional Information

  • Chromosomes are a collection of thread-like structures that come in different lengths and forms.
    • DNA and proteins (mainly histones) make up chromosomes.
    • Genes are carried on chromosomes.
    • They are located in the nucleus of eukaryotic cells.
    • Chromosomes in humans can be divided into autosomes and sex chromosomes.
      • Humans have 22 pairs of autosomes and one pair of sex chromosomes.
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