Question

Crossing over occurs between
A. Two non-sister chromatids of a homologous pair of chromosomes
B. Two chromatids of any chromosome
C. Two chromatids of the same chromosome
D. All the foregoing

Answer 1

Hint: Every person has distinct characteristics of their own. These features have been passed down to them for centuries, but they are all new. Such features are either inherited or gained over the years. Genetic features are transmitted from parents to offspring. The DNA present in individuals carries these. In the chromosomes of all beings, DNA (genetic material) is present. Crossing over is the swapping of chromosome segments while the development of gametes among non-sister chromatids.

Complete answer: The chromosomes are classified as long thread-like structures composed of proteins and deoxyribonucleic acid (DNA) found inside the nucleus of animal and plant cells. They are made up of genetic material and knowledge that is transmitted from parents to offspring. Females have XX chromosomes in a pair and males have XY chromosomes in a pair. Gametes have a single kind of chromosome. When two reproductive cells merge, each with a single copy of the chromosome becomes a single cell. This cell divides and further divides the successive cells, which ultimately results in the development of an individual with a complete collection of paired chromosomes. Each chromosome is duplicated during cell division, this step is referred to as the S phase, in which the centromere joins them. These chromosomal copies that are joined are known as sister chromatids. Chromosomes in their compact form are aligned during cell division in the center of the cell and can be observed and distinguished as they are visible in this process under a light microscope. This process is referred to as the metaphase. Chromosomal fusion happens during sexual reproduction and is the sharing of genetic material. The results of crossing over are no longer similar in the chromatids joined by centromeres. Crossing over is important during meiosis for the natural segregation of chromosomes. Between prophase-I and metaphase-I of cell division, the chromosomal crossing over happens. Two homologous non-sister chromatids pair up and exchange various segments of genetic material that result in recombinant chromosomes during this process. Meiosis ll entails chromosomal isolation and daughter cell administration of recombinant alleles. Because of this, the offspring has a different set of genes and alleles than their parents.
Therefore, choice A, i.e., homologous chromosome non-sister chromatids, is the correct answer.

Note: The first German biologist to discover cell division was Walther Flemming. He introduced the chromatic phrase. He was the founder of cytogenetics as well. The analysis of chromosomal structure, function and position in the cell is cytogenetics. The chromosomes were first recognized by Virchow, Butschlii, and Schleiden, German scientists. The German scientist Von Waldeyer-Hartz coined the word chromosome.