How do homologous chromosomes differ from chromatids

The two copies of a chromosome are called sister chromatids. However, as soon as they are pulled apart during cell division, each is considered a separate chromosome. Medical Definition of sister chromatid : either of the two identical chromatids that are formed by replication of a chromosome during the S phase of the cell cycle, are joined by a centromere, and segregate into separate daughter cells during anaphase.

Sister chromatids are exact copies of each other and are formed just prior to cell division. After mitosis, sister chromatids contain the same genes, but they may have different alleles. Sister chromatids are produced during mitosis. All of these statements about sister chromatids are TRUE. A chromatid is one of two identical halves of a replicated chromosome. During cell division, the chromosomes first replicate so that each daughter cell receives a complete set of chromosomes.

In some species, sister chromatids serve as the templates of DNA repair. Homologous chromosomes are chromosome pairs with a similar length, centromere position and staining patterns. Each homologue of homologous chromosome pair is inherited either by paternally or maternally. Even though they are similar, these chromosomes are not identical as they are inherited from two different individuals.

Each homologous chromosome contains two chromosomes, and they do not stick together. But when the replication process starts, the homologous pairs replicate itself and produce two identical DNA molecules. As they become more condensed, they become visible as two strands called chromatids.

Homologous chromosomes are composed of both maternal and paternal chromosomes. Therefore, different alleles of the same gene can be found most of the times. On the other hand, sister chromatids are composed of same allele of a gene in both strands since they are synthesized by the DNA replication of a strand. Thus, the key difference between homologous chromosomes and sister chromatids is in their genetic composition. Reference: 1. Pearson — The Biology Place. Accessed 12 Feb. Wikipedia , the free encyclopedia.

Mccarthy E. Online Biology Dictionary. Accessed 17 Feb. Image Courtesy: 1. By Bolzer et al. View all posts. Leave a Reply Cancel reply. In meiosis II, these two sister chromatids will separate, creating four haploid daughter cells. In humans, the nucleus typically contains 46 chromosomes. Thus, there are 22 pairs of autosomes with approximately the same length, staining pattern, and genes with the same loci.

As for the sex chromosomes, the two X chromosomes are considered as homologous whereas the X and Y chromosomes are not. A pair of chromosomes made up of two homologs. Homologous chromosomes have corresponding DNA sequences and come from separate parents; one homolog comes from the mother and the other comes from the father. Homologous chromosomes line up and synapse during meiosis. The two chromosomes in a homologous pair are very similar to one another and have the same size and shape.

Most importantly, they carry the same type of genetic information: that is, they have the same genes in the same locations. There are now two cells, and each cell contains half the number of chromosomes as the parent cell. In addition, the two daughter cells are not genetically identical to each other because of the recombination that occurred during prophase I Figure 4.

Homologous chromosomes are not identical.