Study the diagram given below which represents a stage during the mitotic cell division and answer the questions that follow: Study the diagram given below which represents a stage during the mitotic cell division and answer the questions that follow:
Mention the stage that comes before the stage shown in the diagram. Draw a neat labelled diagram of the stage mentioned.
Topic: Anaphase — diagram
Answer
The stage before telophase is ANAPHASE.
Your diagram must show: • the CENTROMERES SPLIT, so each chromatid is now an independent DAUGHTER CHROMOSOME • the daughter chromosomes MOVING TOWARDS OPPOSITE POLES, drawn V or J shaped with the arms trailing behind • SPINDLE FIBRES attached to the centromeres and contracting • NO nuclear membrane and NO nucleolus (both disappeared in prophase)
Labels required: daughter chromosome, centromere, spindle fibre, pole.
THE FEATURE THAT MUST BE RIGHT is the V OR J SHAPE of the moving chromosomes. The spindle fibre pulls at the CENTROMERE, so the arms trail behind like a towed object — which is why they bend. Drawing them straight loses the point.
THE DEFINING EVENT of anaphase is the SPLITTING OF THE CENTROMERE. Until that instant the two chromatids are one chromosome; the moment it divides they become two, and the cell briefly contains double the usual number.
COUNT CAREFULLY if asked: the number of chromosomes moving to ONE pole is the chromosome number of the parent cell. Counting everything in the cell doubles your answer.