1.Interphase is an important and the longest phase of the cell cycle during which the cell prepares for division by coping its DNA. It is metabolic phase of the cell, in which the cell grows, obtains nutrients and metabolizes them. There are three stages of interphase: G1 (the cell growth), S (replication of DNA, chromosomes are copied) and G2 (preparation for division). Without this phase, genetic material wouldn’t be ready for the process of meiosis and haploid gametes couldn’t be created.
2.Homologous chromosomes are the similar but not totally identical chromosome pairs that an organism receives from its two parents. During the prophase I of meiosis they pair up: each chromosome aligns with its homologue partner via link-chiasmata ( the two match up at corresponding positions). Those homologue pairs separate during a first stage of cell division (meiosis I-reduction of chromosomes number, from diploid to haploid), while sister chromatids separate during a second stage (meiosis II).
3.Crossing over is a process in which homologous chromosomes trade their parts. Crossing over is process of genetic recombination where DNA is cut and then repaired. Cut and repair of homologous chromosomes allow them to exchange some of their genetic information. As a consequence of crossing over, new arrangement of maternal and paternal alleles on the same chromosome is achieved. It is the way to create varations.
4.During the metaphase I, homologue pairs are lined up comparing to metaphase II where individual chromosomes are lined up. It is because during the meiosis I homologue pairs separate and chromosome number reduce from diploid to haploid. On the other hand, during the meiosis II, sister chromatids separate.
5.Nondisjunction is the consequence of cell division, where there is no properly separation. There are different forms of nondisjunction:
•failure of a pair of homologous chromosomes to separate in meiosis I,
•failure of sister chromatids to separate during meiosis II.
After nondisjunction, resulting daughter cells are with abnormal chromosome numbers -aneuploidy.
Homologous chromosomes have same size, morphology, and have similar genetic constitution.
The homologous chromosome is the pair of maternal and paternal chromosomes that share the same morphology. The homologous chromosomes are genetically similar since the alleles of a particular gene occupy the corresponding position on these chromosomes.
Therefore, a specific locus of homologous chromosomes carries alleles of the same gene. The homologous chromosomes pair up during zygotene of prophase I and undergo crossing over followed by their segregation during anaphase-I.
The cell cycle refers to an ordered flow of events, which includes cell growth as well as cellular division. This cycle produces two new daughter cells. The cycle starts with interphase in this the cell mature and replicates its DNA or deoxyribonucleic acid. The interphase begins with:G1 phase: This is the primary growth phase to provide nutrients to the cell. If a cell doesn’t have a sufficient amount of proteins or other raw materials for the replication of DNA. S phase or synthesis of DNA: During this phase, the replication of DNA takes place. The centrosome is dividing and forms a mitotic spindle during the mitosis phase. A mistake in this phase will lead to the loss of DNA mutations or integrity. G2 or second gap: during this phase, the cell mainly replenishes its energy stores as well as synthesizes the proteins which are required for the chromosome manipulation. In this phase, an error is resolved even in case of an unresolved error; the cell undergoes division to pass on the error to the daughter cell.
The second stage of a cell cycle is the mitosis or M phase. Chromosomal abnormalities can occur during the metaphase of meiosis. It would lead to aneuploidy or polyploidy, due to unequal division of chromosomes. Mitotic phase refers to a multiphase process in this the chromosomes are aligned, segregated, and moved into the two new daughter cells, which are identical to each other.
Metaphase: In this stage, the formation of spindle fibers is completed and centrosomes are found at the opposite terminals of the cell. The chromosomes line up at the metaphase plate. Each of the sister chromatids is linked to the spindle fiber starting from the opposite poles. In this phase, one problem occurs, which is chromosomes don’t line up perfectly.
Crossing over is the exchange of segments of chromosomes between non-sister chromatids during meiosis. This process results in new combinations of genes in the gametes from each parent and thus contributing to genetic diversity among organisms.
Learn more:Learn more about the abiotic factor Learn more about the cellular respiration Learn more about the primary and secondary succession
Grade: High School
Mitosis, meiosis, cell division, anaphase, telophase, cytokinesis, prophase, metaphase, segregation, chromosome.