Types of Eukaryotic Chromosomes Based on Centromeres

 Types of Eukaryotic Chromosomes Based on Centromeres

Types of chromosomes based on Centromere 

Eukaryotic chromosomes are thread-like structures composed of DNA and histone proteins that carry genetic information. Each chromosome consists of a centromere, arms, and telomeres. The centromere is a constricted region crucial for the movement of chromosomes during cell division, as it attaches to spindle fibers. Based on the position of the centromere, eukaryotic chromosomes are classified into four main types — metacentric, submetacentric, acrocentric, and telocentric.

1. Metacentric Chromosomes

1. Centromere position: In the middle.l

2. Arm length: Both arms are equal in length.

3. Shape during anaphase: V-shaped.

 Example: Human chromosome 1.

2. Submetacentric Chromosomes

1. Centromere position: Slightly off-center.

2. Arm length: One arm is shorter than the other.

3. Shape during anaphase: L or J-shaped.

Example: Human chromosomes 4 and 6.

3. Acrocentric Chromosomes

1. Centromere position: Close to one end.

2. Arm length: One arm is very long, the other is very short (often with a satellite).

3. Shape during anaphase: Rod-like with satellite.

Example: Human chromosomes 13, 14, 15, 21, and 22.

4. Telocentric Chromosomes

1. Centromere position: At the terminal end.

2. Arm length: Only one arm is present.

3. Shape during anaphase: I-shaped.

Example: Found in mice, absent in humans.

Summary Table

Type Centromere Position Arm Length Shape in Anaphase Example

Metacentric Middle Equal V-shaped Human Chromosome 1

Submetacentric Slightly off-center Unequal L or J-shaped Human Chromosome 4

Acrocentric Near one end One very short, one long Rod with satellite Human Chromosome 13

Telocentric At terminal end One arm only I-shaped Mouse Chromosomes

FAQs

Q: What is a centromere?

A: A constricted region of a chromosome that helps in spindle fiber attachment during cell division.

Q: How do metacentric and acrocentric chromosomes differ?

A: Metacentric chromosomes have equal arms, while acrocentric chromosomes have one very short and one very long arm.

Q: Which type of chromosomes are not found in humans?

A: Telocentric chromosomes are absent in humans but present in mice.

Q: Why is centromere position important?

A: It helps in identifying chromosomes during karyotyping and understanding their behavior in cell division.

Q: Which human chromosomes are acrocentric?

A: Chromosomes 13, 14, 15, 21, and 22 are acrocentric.

Multiple Choice Questions (MCQs)

Q: The centromere in a metacentric chromosome is located:

Answer: b) In the middle

Q: Submetacentric chromosomes appear as:

Answer: b) L or J-shaped

Q: Acrocentric chromosomes are characterized by:

Answer: b) Short and long arms with satellite

Q: Telocentric chromosomes occur in:

Answer: b) Mice

Q: Which type of chromosome has the centromere near one end?

Answer: Acrocentric

Worksheet

A. Fill in the blanks:

1. The _______ helps chromosomes attach to spindle fibers.

2. _______ chromosomes have the centromere at the middle.

3. Human chromosomes 13, 14, 15, 21, and 22 are _______.

4. _______ chromosomes are absent in humans.

5. During anaphase, metacentric chromosomes appear _______ shaped.

B. Match the following:

Metacentric — V shape

Submetacentric — L shape

Acrocentric — Satellite present

Telocentric — I shape

References

Alberts, B. et al. (2022). Molecular Biology of the Cell. 7th Edition. Garland Science.

De Robertis, E.D.P. & De Robertis, E.M.F. (2001). Cell and Molecular Biology.

Lodish, H. et al. (2021). Molecular Cell Biology. 9th Edition. W.H. Freeman.

zoologys.co.in – Cell Biology Notes and Practicals.