Problem 73 - Objective Biology for NEET

Question

Meiosis occurs in (a) Liver (b) Kidney (c) Gonad (d) Brain

Step-by-Step Solution

Answer

Meiosis occurs in the Gonad (Option c).

Step 1: Understanding Meiosis

Before approaching the exercise, it's essential to understand what meiosis is. Meiosis is a type of cell division where one cell divides twice to form four daughter cells. These daughter cells are genetically different from each other and contain half the number of chromosomes compared to the parent cell.

Step 2: Identifying Where Meiosis Happens

Next, understand that meiosis is closely associated with sexual reproduction, thus it only occurs in certain cells within the organism - the germ cells. Germ cells are the cells that give rise to gametes (sperm and egg cells). So, one should look for an organ that is associated with sexual reproduction.

Step 3: Match with the Options

Looking at the list: liver, kidney, gonad, and brain, the organ that is associated with sexual reproduction is the gonad. The gonads are the primary reproductive organs, they produce the germ cells and hormones needed for reproduction. In males, they are termed testes, and in females, they are called ovaries.

Key Concepts

Understanding Meiosis in Cell Division

Meiosis is a specialized form of cell division essential for sexual reproduction. Unlike mitosis, which creates two identical daughter cells, meiosis results in four genetically unique daughter cells, each with half the number of chromosomes of the original cell. This reduction is crucial because it ensures that when gametes from two parents unite during fertilization, the resulting offspring has the correct number of chromosomes.

During meiosis, one round of DNA replication is followed by two rounds of cell division, termed meiosis I and meiosis II. Meiosis I reduces the chromosome number by half, and meiosis II, similar to mitosis, separates the sister chromatids. This sequence of events leads to genetic diversity through processes such as crossing over, where segments of DNA are exchanged between homologous chromosomes, and independent assortment, the random distribution of maternal and paternal chromosomes to the gametes.

Gametogenesis: Formation of Gametes

Gametogenesis is the process by which germ cells undergo meiosis to form gametes - sperm in males (spermatogenesis) and eggs in females (oogenesis). It is an intricate and highly regulated process that ensures the transfer of genetic information from parents to offspring.

In males, spermatogenesis occurs in the testes and results in the production of millions of sperm daily. On the other hand, oogenesis takes place in the ovaries and is a more prolonged process, producing a single mature egg per menstrual cycle. Due to the reductional division involved in meiosis, each gamete contains only one set of chromosomes, making them haploid. This is vital, as it allows for the diploid state to be restored upon fertilization when two haploid gametes merge.

Sexual Reproduction: Combining Genetic Material

Sexual reproduction is a biological process where two individuals contribute genetic material to produce a new organism. It contrasts with asexual reproduction, where offspring arise from a single organism, inheriting the genes of that parent only. The beauty of sexual reproduction lies in the genetic variation it promotes, which is a cornerstone of evolutionary adaptation and species survival.

During sexual reproduction, the union of male and female gametes during fertilization forms a zygote. The zygote undergoes multiple rounds of cell division and developmental processes to become a mature organism. This diversity results from genetic recombination during meiosis and the random pairing of gametes from each parent. In this context, meiosis provides a mechanism for shuffling the genetic deck, an evolutionary advantage that helps in the natural selection process.