Question

The size of the linkage group depends on the size of the chromosome. If the chromosome is long enough, and the genes are located sufficiently far apart on the chromosomes, events in which of the following stages of cell division might cause the genes to be inherited independently of each other?

• A. Prophase I
• B. Anaphase I
• C. Prophase II
• D. Anaphase II

Answer 1

The correct option is A Prophase I


The image given above shows crossing over and recombination in homologous chromosomes.
Homologous chromosomes are paired chromosomes. Each chromosome is inherited from a parent and they are similar in their morphology and structure. They also have alleles for the same gene (the alleles may be either identical or non identical) and located at the same loci. Each chromosome is made up of 2 sister chromatids and the chromatids of the two homologous chromosomes are known as non-sister chromatids.
Crossing over is a phenomenon in which there is exchange of genetic material between non-sister chromatids of homologous chromosomes. If the genes are located sufficiently far apart on a chromosome, then there is a high probability that the genes might get separated due to crossing over. This would eventually cause them to be inherited independently.
In meiosis I, prophase I is divided into five substages- leptotene, zygotene, pachytene, diplotene, and diakinesis. Crossing over occurs during the pachytene stage of prophase I.
In anaphase I, there is separation of homologous chromosomes with sister chromatids remaining intact.
In prophase II, the nuclear membrane disappears and the chromosomes become more compact.
In anaphase II, sister chromatids are separated from each other and start moving towards opposite poles.