Question

Crossing over is an exchange of genetic material between (a) Homologous chromosome (b) Heterologus chromosome (c) Non-homologous chromosome (d) All of these

Short answer

Based on the understanding of crossing over in genetics, it is clear that the exchange of genetic material happens between homologous chromosomes. Therefore, the correct answer is 'Homologous chromosome'.

Step-by-step solution

Understanding Crossing Over

For any living organism, genetic variability is an important factor for survival and evolution. One such method of genetic variation in eukaryotes (organisms with a nucleus) is crossing over. Crossing over is a process that occurs during meiosis (a type of cell division) in which paired chromosomes (homologous chromosomes) exchange genetic information.

Identifying Homologous Chromosomes

Homologous chromosomes are chromosome pairs of approximately the same length and genes, each deriving from one parent. They pair up with each other inside a cell during meiosis. Because of their similar structure and genetic information, crossing over can take place between homologous chromosomes.

Disregarding Other Options

A) Heterologous chromosomes are non-identical chromosomes, hence cannot undergo crossing over. B) Non-homologous chromosomes, with different sets of genes, cannot exchange genetic materials. C) Therefore, only homologous chromosomes, with their identical structure and genetic information, can undergo crossing over. Hence, we can disregard the options 'Heterologous chromosome', 'Non-homologous chromosome', and 'All of these'.

Key concepts

Genetic Variability

Genetic variability is the cornerstone of biodiversity and evolution. It refers to the differences in genetic makeup within and between populations of a species. These variations arise through mutations, gene flow, and sexual reproduction, providing a palette from which natural selection can 'paint' and help species adapt to ever-changing environments.

One of the most significant contributions to genetic variability is crossing over during meiosis. Imagine it like swapping sections of a recipe between two very similar cookbooks—it's this exchange of genetic segments that increases the number of different genetic combinations that can be passed on to offspring. This mixing of genetic material ensures that no two siblings (except identical twins) are genetically identical, which is hugely beneficial for the species' ability to survive and thrive amidst diverse environmental challenges.

Meiosis

Think of meiosis as a sophisticated dance that chromosomes perform, where the end game is to produce gametes—eggs in females and sperm in males. Meiosis is a two-stage type of cell division that reduces the chromosome number by half. This means that from a parent cell with two sets of chromosomes (diploid), four daughter cells are produced, each containing one set of chromosomes (haploid).

During meiosis I, homologous chromosomes line up and exchange genetic material through crossing over. This stage is critical for shuffling genes and contributes to the genetic uniqueness of each gamete. Later, in meiosis II, sister chromatids separate, much like in mitosis. The final result? Four unique gametes, awaiting fertilization to combine and begin the life of a new, genetically varied organism. It's this process that ensures sexual reproduction brings together these diverse genetic combinations, promoting the health and adaptability of species.

Homologous Chromosomes

Homologous chromosomes are kind of like a pair of shoes—they look very similar, but there's a right and a left, corresponding to the pair of chromosomes, one inherited from each parent. They are of the same length, have the same centromere position, and carry the same genes, although the versions (alleles) of those genes may differ.

The significance of homologous chromosomes comes into play during meiosis when they pair up and exchange parts of their genetic information through crossing over. This crossing over is like les jeux d'amour et du hasard where two allies exchange their secrets to generate new, unique combinations that contribute to the genetic diversity seen in offspring. It's this precise homology that allows for the accurate and equivalent exchange of genes, ensuring that genetic information is shuffled but not lost or corrupted, preserving the integrity of the cell's genetic code.