Question

The stage between two meiosis is (a) M-phase (b) Interphase (c) S-phase (d) Interkinesis

Short answer

The stage between two instances of meiosis is (d) Interkinesis.

Step-by-step solution

Understand Meiosis

Meiosis is a type of cell division that results in four daughter cells, each with half the number of chromosomes of the parent cell. It consists of two stages, Meiosis I and Meiosis II, each of which involves several phases such as prophase, metaphase, anaphase, and telophase.

Identify the Stage Between Two Meiosis

Between two instances of meiosis (Meiosis I and Meiosis II), cells go into a brief period of rest. During this phase, the cell does not replicate its DNA. This stage is known in biology as the interkinesis or interphase II.

Match with Given Options

Look at the options given in the exercise. The correct answer is the one that matches the stage identified in Step 2. In this case, the answer is interkinesis.

Key concepts

Meiosis

Meiosis is a special type of cell division crucial for sexual reproduction. During meiosis, cells divide to produce gametes, which are sperm or egg cells in animals, and pollen or ovule in plants. What sets meiosis apart is that it reduces the chromosome number by half, creating haploid cells from a diploid parent cell. This reduction is essential to maintain the species' chromosome number through generations.

• Meiosis occurs in two major rounds of division: Meiosis I and Meiosis II.
• Each round has distinct phases: prophase, metaphase, anaphase, and telophase.
• The end result is typically four genetically diverse haploid daughter cells.

One fascinating aspect of meiosis is how it contributes to genetic variation, allowing species to adapt and evolve over time. This variation occurs due to processes like crossing over and independent assortment.

Cell Division

Cell division is a fundamental process by which cells reproduce. It is important for growth, development, and repair in all living organisms. There are two primary types of cell division: mitosis and meiosis. While mitosis results in identical daughter cells, meiosis results in genetically distinct cells.

• Mitosis is common in somatic cells and is responsible for growth and maintenance.
• Meiosis is distinctive to the production of gametes for sexual reproduction.

Cell division ensures that each new cell receives the correct amount of DNA. In the case of meiosis, it helps in maintaining the genetic diversity of organisms by ensuring the right distribution of chromosomes.

Stages of Meiosis

The stages of meiosis are organized into two sequential phases: Meiosis I and Meiosis II. Each has specific sub-stages: prophase, metaphase, anaphase, and telophase, which ensure proper segregation of chromosomes.

Meiosis I

In Meiosis I, homologous chromosomes pair up and then segregate into different cells. This process reduces the chromosome number from diploid to haploid.

• Prophase I: Chromosomes condense and crossing over occurs, exchanging genetic material.
• Metaphase I: Homologous chromosomes align at the equatorial plate.
• Anaphase I: Homologous chromosomes are pulled apart to opposite poles.
• Telophase I: Chromosomes reach the poles and the cell divides.

Meiosis II

Meiosis II resembles a typical mitotic division, but it involves the separation of sister chromatids.

• Prophase II: Chromosomes coil again and the spindle forms.
• Metaphase II: Chromosomes line up at the equator.
• Anaphase II: Sister chromatids are separated and pulled toward opposite poles.
• Telophase II: Chromatids reach the poles, and the cells divide, resulting in four haploid cells.

Chromosome Reduction

Chromosome reduction is a critical component of meiosis, specifically occurring during Meiosis I. It ensures that gametes have half the chromosome number compared to somatic cells. This process avoids doubling the chromosome number during fertilization.

In humans, for instance, somatic cells possess 46 chromosomes, while gametes contain just 23. The reduction is achieved by the reduction division in Meiosis I:

• During prophase I, synapsis and crossing over occur, setting the stage for genetic diversity.
• Anaphase I is where homologous chromosomes, not sister chromatids, are pulled apart, effectively reducing the chromosome number by half.

By halving the chromosome number, meiosis prevents any increase in the chromosome count through generations and sustains genetic variation. This reduction is vital for creating balanced gametes ready for fertilization.