Question

The point of attachment for two sister chromatids is the a. centriole. c. chromosome. b. centromere. d. karyotype.

Short answer

The point of attachment for two sister chromatids is the centromere (Option B).

Step-by-step solution

Option A: Centriole

Centriole is a cylindrical cell structure found in most eukaryotic cells, which is involved in cell division, specifically in the formation of spindle fibers. This is not the point of attachment for sister chromatids.

Option B: Centromere

Centromere is the specialized region on a chromosome, where sister chromatids are joined and held together. This is the structure that allows the sister chromatids to be properly segregated during cell division. This is the correct answer.

Option C: Chromosome

A chromosome is a long molecule of DNA that is condensed and wrapped around proteins called histones, which carries genetic information. Chromosomes contain many genes, regulatory elements, and noncoding DNA. This is not the point of attachment for sister chromatids.

Option D: Karyotype

A karyotype is the number, size, and shape of chromosomes in an organism, as seen during cell division. It is a representation of the entire set of chromosomes of an organism and is used to study chromosomal abnormalities. This is not the point of attachment for sister chromatids. Based on our analysis, the correct answer is:

Correct Answer

The point of attachment for two sister chromatids is the centromere (Option B).

Key concepts

Understanding Sister Chromatids Attachment

The connection between two sister chromatids is a fundamental aspect of genetics and cell biology. Sister chromatids are identical copies of a single chromosome that are produced during the S phase of the cell cycle, which is a part of interphase. They are crucial for the accurate segregation of genetic material during cell division.

The point of attachment for these chromatids is called the centromere. It's not just a point of convergence; the centromere plays a critical role in chromosome movement during cell division. It's the region where spindle fibers, which emerge from the centrosomes at each pole of the cell, attach to the chromosomes through protein structures called kinetochores. This attachment is essential, as it helps pull chromatids apart during anaphase, ensuring that each new cell receives the correct number of chromosomes.

Important Functions of the Centromere

• Hold sister chromatids together: Ensures correct alignment and separation during cell division.
• Connection for spindle fibers: Facilitates the movement of chromosomes towards opposite poles.
• Regulation of gene expression: Can influence the activity of certain genes near the centromere region.

The centromeres' position can vary, leading to the classification of chromosomes as metacentric, submetacentric, acrocentric, or telocentric, reflecting the centromere's location along the chromatid's length.

The Phases of Cell Division

Cell division is a critical process for the growth and repair of tissues in multicellular organisms, as well as for reproduction in unicellular organisms. It is classified into two main types: mitosis and meiosis.

Mitosis is the division of a parent cell into two genetically identical daughter cells, each containing the same number of chromosomes as the original cell. Meiosis, on the other hand, leads to the formation of gametes or sex cells, which have half the number of chromosomes as the parent cell.

Both processes have several phases:

• Interphase: Before division begins, cells prepare by increasing in size and duplicating their DNA.
• Prophase: Chromosomes condense, spindle fibers form, and the nuclear envelope breaks down.
• Metaphase: Chromosomes align at the cell's equatorial plate.
• Anaphase: Spindle fibers retract, pulling sister chromatids apart to opposite poles.
• Telophase and Cytokinesis: Two nuclei form, and the cell divides into two separate cells.

Understanding the minutiae of each phase can illuminate how disruptions in the process may lead to diseases, like cancer, which often involve uncontrolled cell division.

Chromosomes: The Carriers of Genetic Information

Chromosomes are thread-like structures located within the nucleus of animal and plant cells. Composed of DNA wound tightly around proteins called histones, chromosomes are the vehicle for transmitting genetic information from one generation to the next.

Each species has a characteristic number of chromosomes. In humans, there are 46 chromosomes, organized into 23 pairs. One set of 23 comes from the mother, and the other set from the father. Within these structures, genes are found at specific loci, and they determine every biological trait, from eye color to potential susceptibility to certain diseases.

Structural Features of Chromosomes:

• P arm: The short arm of the chromosome.
• Q arm: The long arm of the chromosome.
• Telomeres: Protective caps at each end of a chromosome.
• Origins of replication: Sites where DNA replication begins.

Studying chromosomes is pivotal in various scientific fields, including genetics, molecular biology, and medical diagnostics. Abnormalities in chromosome number or structure can result in genetic disorders, making chromosome analysis (karyotyping) an essential tool in genetics and prenatal screening.