Problem 161 - Objective Biology for NEET

Question

Match the column: Column I Column II A. Metacentric chromosomal 1\. Middle centromere B. Sub-metacentric 2\. Centromere slightly way from middle C. Acrocentric 3\. Centromere close to its end D. Telocentric 4\. Terminal centromere (a) \(\mathrm{A}-1, \mathrm{~B}-2, \mathrm{C}-3, \mathrm{D}-4\) (b) \(\mathrm{A}-2, \mathrm{~B}-1, \mathrm{C}-3, \mathrm{D}-4\) (c) A-1, B-2, C-4, D-3 (d) \(\mathrm{A}-4, \mathrm{~B}-3, \mathrm{C}-2, \mathrm{D}-1\)

Step-by-Step Solution

Answer

\(\mathrm{A}-1, \mathrm{~B}-2, \mathrm{C}-3, \mathrm{D}-4\).

Step 1: Understanding the Terms

First, it is important to know what each term means. Metacentric chromosome refers to a chromosome where the centromere is in the middle, Sub-metacentric is when the centromere is slightly away from the middle, Acrocentric refers to a chromosome in which the centromere is close to its end and Telocentric refers to a chromosome where the centromere is at the terminal or end position.

Step 2: Matching the Terms with their Definitions

Now, match the terms from Column 1 with the definitions in Column II. Metacentric chromosome matches with 'Middle centromere', corresponding to 1 in Column II. Sub-metacentric matches with 'Centromere slightly way from middle', corresponding to 2 in Column II. Acrocentric corresponds to 'Centromere close to its end', which is 3 in Column II, and Teleocentric matches with 'Terminal centromere', which is 4 in Column II.

Key Concepts

Metacentric chromosome

A metacentric chromosome is characterized by having its centromere located in the middle, creating two arms of almost equal length. This configuration gives the chromosome an "X" shape, making it relatively symmetrical.
While studying chromosomes, identifying their centromere position is crucial for understanding their structure and function. In most cases, the metacentric arrangement can be advantageous during cell division, as the forces applied on either side of the centromere are more evenly distributed.
Key Points about Metacentric Chromosomes:

• The centromere is exactly in the middle.
• Both arms of the chromosome are nearly equal in length.
• They provide better equilibrium during cell division.

If you imagine trying to "balance" a chromosome like a seesaw, a metacentric chromosome is the easiest to balance because of its symmetry.

Sub-metacentric chromosome

Sub-metacentric chromosomes have a centromere that is slightly off-center, leading to one arm being slightly longer than the other. This results in a chromosome shape that resembles an "L" or a "J".
The position of the centromere plays an important role in genetic studies and also impacts the movement of chromosomes during the cell division process. Despite the asymmetry, sub-metacentric chromosomes remain quite functional across various cell types.
Key Characteristics of Sub-metacentric Chromosomes:

• Centromere is off-center but not too close to the end.
• Creates a distinct "L" or "J" shape.
• One arm is noticeably longer than the other.

This slight imbalance in arm length can impact chromosome movement, but it also supports unique genetic arrangements and functions.

Acrocentric chromosome

When a chromosome has its centromere located very close to one end, it is categorized as acrocentric. This gives rise to one very long arm and one very short arm, often described as "satellite arms".
Acrocentric chromosomes are crucial in certain genetic functions and can carry important genes. These chromosomes are especially interesting in genetics due to their role in constructing the nucleolus and their involvement with ribosomal RNA. Key Traits of Acrocentric Chromosomes:

• Centromere is near one end of the chromosome.
• Results in one very long and one very short arm.
• Associated with nucleolus formation and ribosomal RNA.

Acrocentric chromosomes play specific roles in cellular processes, making them a topic of interest in genetic studies and medicine.

Telocentric chromosome

Telocentric chromosomes are distinct because their centromere is located at the very end of the chromosome. This means there is effectively only one arm, giving it a characteristic "I" shape when viewed under a microscope.
These chromosomes are less frequently found in humans but are more common in some other organisms. Their unique structure can affect how they are segregated during cell divisions, which is vital in studies of chromosomal behavior. Key Aspects to Note about Telocentric Chromosomes:

• Centromere is at the terminal, or end position.
• Presents with a single arm, resembling an "I" shape.
• Less common in humans, more prevalent in non-human species.

Understanding telocentric chromosomes is important for specific genetic applications and comparative studies among species.