Question

Crossing over occurs between
A. Sister chromatids of homologous chromosome
B. Non-sister chromatids of homologous chromosome
C. Sister chromatids of a non-homologous chromosome
D. Non-sister chromatids of a non-homologous chromosome

Answer 1

Every individual has their own distinct characteristics. These characteristics are passed down to them from generations but they all are unique. These characteristics are either genetic or acquired over the years. Genetic characteristics are passed down from parents to off-springs. These are carried by the DNA present in individuals. DNA(genetic material) is present in the chromosomes of all beings.

Complete step by step answer: Long thread-like structures consisting of proteins and deoxyribonucleic acid (DNA) located within the animal and plant cell nucleus are known as chromosomes.
-They consist of genetic material and information which is passed from parents to off-springs. Females have a pair of XX chromosomes and males have a pair of XY chromosomes. Gametes contain a single chromosome of a type.
-When two reproductive cells fuse, they become a single cell with each of a single copy of the chromosome. This cell divides and the successive cells further divide which eventually results in the production of an individual containing a full set of paired chromosomes.
-During cell division, each chromosome is duplicated, this phase is known as the S phase, wherein they are joined by the centromere. These joined chromosomal copies are known as sister chromatids. -Chromosomes in their condensed form are aligned in the center of the cell during cell division and can be studied and distinguished as they are visible under a light microscope in this phase. This phase is known as the metaphase.
-Chromosomal crossover occurs during sexual reproduction and is the exchange of genetic material.
Crossing over results in the chromatids joined by centromeres no longer being identical. During meiosis for the normal segregation of chromosomes, crossing over is essential. The chromosomal crossing over occurs between prophase-I and metaphase-I of cell division. During this process, two homologous non-sister chromatids pair up and exchange different segments of genetic material that results in recombinant chromosomes. Meiosis ll involves the separation of chromosomes and administration of recombined alleles in daughter cells. Due to this, the offspring has a different set of genes and alleles than their parents.
Hence, the correct answer is option B, i.e., Non-sister chromatids of homologous chromosome

Note: Walther Flemming was the first German biologist to discover cell division. He introduced the term Chromatin. He also was the founder of Cytogenetics. Cytogenetics is the study of chromosomal
structure, function, and location in the cell. The chromosomes were first recognized by the German
scientists Virchow, Butschlii, and Schleiden. The word chromosome was coined by German scientist
Von Waldeyer-Hartz.