Class 11 Biology - Chapter Cell: The Unit of Life NCERT Solutions | What is a centromere? How does the posit
What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.
Centromere is a constriction present on the chromosomes where the chromatids are held together.
Chromosomes are divided into four types based on the position of the centromere.
(i) Metacentric chromosome
The chromosomes in which the centromere is present in the middle and divides the chromosome into two equal arms is known as a metacentric chromosome. During anaphase, they appear V-Shaped.
(ii) Sub-metacentric chromosome
The chromosome in which the centromere is slightly away from the middle region is known as a sub-metacentric chromosome. In this, one arm is slightly longer than the other. During anaphase, they appear L-Shaped.
(iii) Acrocentric chromosome
The chromosome in which the centromere is located close to one of the terminal ends is known as an acrocentric chromosome. In this, one arm is extremely long and the other is extremely short. During anaphase, they appear J-Shaped.
(iv) Telocentric chromosome
The chromosome in which the centromere is located at one of the terminal ends is known as a telocentric chromosome. During anaphase, they appear i-Shaped.
More Questions From Class 11 Biology - Chapter Cell: The Unit of Life
- Q:-
Name two cell-organelles that are double membrane bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both.
- Q:-
Multicellular organisms have division of labour. Explain.
- Q:-
Cell is the basic unit of life. Discuss in brief.
- Q:-
What is a mesosome in a prokaryotic cell? Mention the functions that it performs.
- Q:-
Which of the following is correct:
(a) Cells of all living organisms have a nucleus.
(b) Both animal and plant cells have a well defined cell wall.
(c) In prokaryotes, there are no membrane bound organelles.
(d) Cells are formed de novo from abiotic materials. - Q:-
Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.
- Q:-
Describe the structure of the following with the help of labelled diagrams.
(i) Nucleus
(ii) Centrosome - Q:-
What are nuclear pores? State their function.
- Q:-
How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?
- Q:-
What are the characteristics of prokaryotic cells?
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