Problem 11 - Campbell Biology

Question

EVOLUTION CONNECTION The result of mitosis is that the daughter cells end up with the same number of chromosomes that the parent cell had. Another potential way to maintain the number of chromosomes would be to carry out cell division first and then duplicate the chromosomes in each daughter cell. Assess whether this would be an equally good way of organizing the cell cycle. Explain why evolution has not led to this alternative.

Step-by-Step Solution

Answer

Performing mitosis ensures efficient chromosome distribution and minimizes errors, while the alternative would be less efficient and prone to errors in duplication.

Step 1 - Review Mitosis

Understand that mitosis involves one round of nuclear division where the chromosomes are duplicated beforehand and then equally distributed to two daughter cells. This ensures each daughter cell has the same number of chromosomes as the parent cell.

Step 2 - Consider Alternative Division First

Imagine a scenario where cell division happens first. Each daughter cell would initially have half the number of chromosomes (a haploid state) of the parent cell.

Step 3 - Duplicate Chromosomes Post-Division

Think about the process of replicating DNA in each daughter cell after division. Each daughter cell would need to duplicate its chromosomes to restore the original chromosome number.

Step 4 - Evaluate Practicality

Assess the practicality of post-division chromosome duplication. Consider that division first followed by duplication adds an additional step and possible errors in DNA replication since there would be twice as many replication events.

Step 5 - Evolutionary Perspective

Analyze why evolution has favored mitosis. Mitosis ensures equal distribution of chromosomes efficiently with fewer steps, minimizing the risk of errors during cell division. This efficiency likely provided a selective advantage.

Key Concepts

chromosome duplication

Chromosome duplication is a crucial part of the cell cycle. Each chromosome in the parent cell is replicated to ensure that both daughter cells receive an identical set of chromosomes. This process happens during the S phase of interphase before mitosis. Errors in this step could lead to mutations or diseases.

Chromosome duplication ensures genetic consistency. Daughter cells inherit the same genetic information as the parent cell. This preservation of genetic information is vital for maintaining the organism's characteristics.

During chromosome duplication, the DNA unwinds and enzymes like DNA polymerase help in synthesizing a new strand complementary to each original strand (semi-conservative replication). This way, each new chromosome consists of one old and one new strand of DNA.

cell division

Cell division is the process by which a parent cell divides into two or more daughter cells. It is essential for growth, development, and repair of an organism. In eukaryotic cells, there are two main types of cell division: mitosis and meiosis.

Mitosis results in two daughter cells that are genetically identical to the parent cell. This process includes different steps:

• Prophase
• Metaphase
• Anaphase
• Telophase

Each step ensures the chromosomes are correctly duplicated and evenly distributed. This precision helps in maintaining the organism's genetic stability.

In contrast, meiosis results in four daughter cells, each with half the number of chromosomes of the parent cell. This type of cell division is important for sexual reproduction and genetic diversity.

evolutionary biology

Evolutionary biology seeks to understand the changes in organisms over generations. One aspect of this field examines how cellular processes, like mitosis, have evolved.

The efficiency and reliability of mitosis likely provided a selective advantage to organisms. It minimizes errors in DNA distribution, reducing the risk of genetic disorders.

Evolution favors mechanisms that increase an organism’s survival and reproductive success. The precise replication and equal distribution of chromosomes ensure that genetic information is preserved across generations. As such, mitosis is a highly conserved and efficient process that is central to the evolutionary success of eukaryotic organisms.

mitotic efficiency

Mitotic efficiency refers to how effectively mitosis can replicate and distribute chromosomes. The process is streamlined to ensure minimal errors.

Pre-replicating chromosomes before division reduces the steps and complexity, limiting possible mistakes. Each phase of mitosis has specific checkpoints and mechanisms to correct errors and ensure accurate chromosome segregation.

This level of control ensures cell health and function. When comparing to an alternative process where division happens first, the built-in checks of mitosis show why it is evolutionarily favored.

DNA replication

DNA replication is the process of making an identical copy of a DNA molecule. This occurs during the interphase of the cell cycle, specifically in the S phase, before a cell divides.

Key players in DNA replication include:

• Helicase: Unwinds the DNA strands
• DNA polymerase: Synthesizes the new DNA strand
• Primase: Lays down RNA primers
• Ligase: Joins short DNA fragments

The replication process ensures that each daughter cell has the same genetic material as the parent cell. Accurate replication is critical for maintaining genetic stability.

An alternative method of duplicating chromosomes after cell division would increase the risk of replication errors. By pre-replicating chromosomes, the cell ensures all genetic information is ready to be accurately divided.