All Free Biology MCQs with Answers
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19844 questions · page 583 of 1985
5821. Stage where crossing over occurs in meiosis:
- A. Leptotene
- B. Zygotene
- C. Pachytene
- D. Diplotene
Explanation: Pachytene is where homologous non-sister chromatids exchange segments.
Correct answer: Pachytene5822. Stage with bivalent formation:
- A. Pachytene
- B. Zygotene
- C. Diplotene
- D. Metaphase I
Explanation: Synapsed homologous chromosomes form bivalents during pachytene.
Correct answer: Pachytene5823. Telophase in mitosis is characterized by:
- A. Chromosome condensation
- B. Spindle formation
- C. Nuclear envelope reformation
- D. Chromatid segregation
Explanation: Nuclear envelope reforms, chromosomes decondense, marking end of nuclear division.
Correct answer: Nuclear envelope reformation5824. In metaphase of mitosis:
- A. Chromatids remain in center
- B. Chromatids move toward poles
- C. Golgi & ER visible
- D. Chromosomes align at equator
Explanation: Chromosomes align along equatorial plate for equal segregation.
Correct answer: Chromosomes align at equator5825. Metaphase chromosome attachment occurs via:
- A. Satellites
- B. Secondary constrictions
- C. Kinetochores
- D. Centromeres
Explanation: Kinetochores at centromeres attach spindle fibers.
Correct answer: Kinetochores5826. During cell division, the spindle fibers get attached to condensing chromosome at a highly differentiated region. This region is called as:
- A. Chromosome
- B. Chromocenter
- C. Centriole
- D. Kinetochore
Explanation: During cell division, spindle fibers attach to the kinetochore, which is a highly specialized protein structure located on the centromere of the chromosome.
Correct answer: Kinetochore5827. In a metaphase chromosome diagram, the two identical halves are called:
- A. Chromomeres
- B. Chromatids
- C. Telomeres
- D. Centrioles
Explanation: During metaphase, each chromosome consists of two identical sister chromatids joined at the centromere. These chromatids are the result of DNA replication and will separate during anaphase to form individual chromosomes in daughter cells.
Correct answer: Chromatids5828. In the given diagram showing condensation of chromatin into visible thread‑like structures, chromosomes first appear in which stage?
- A. A
- B. B
- C. C
- D. D
Explanation: During prophase, the chromatin fibers condense to form distinct chromosomes visible under a microscope. Each chromosome consists of two sister chromatids joined at a centromere.This marks the beginning of mitosis, when the genetic material becomes organized for division.
Correct answer: B5829. In a meiosis I diagram, which unique event occurs in the phase labelled as A?
- A. Separation of sister chromatids
- B. Pairing of homologous chromosomes and crossing over
- C. Chromosome replication
- D. Formation of two haploid nuclei
Explanation: Only in Prophase I do homologous chromosomes synapse and exchange genetic material - increasing genetic variation.
Correct answer: Pairing of homologous chromosomes and crossing over5830. In the labeled meiosis II diagram, what happens in the given phase?
- A. Homologous chromosomes separate
- B. Crossing over occurs
- C. Sister chromatids separate
- D. Cytokinesis begins
Explanation: Anaphase II is similar to mitotic anaphase - centromeres divide and chromatids move to opposite poles.
Correct answer: Sister chromatids separate