Table of Contents
Chromosomes are made up of DNA and proteins found in the cytoplasm of the nucleus. In structure they look like thread. Under the light microscope, they can be seen in the metaphase stage, found in the center of the cell. As prokaryotes lacks nucleus, these chromosomes are found in the nucleoid region and are circular in shape. In the plasmid, extrachromosomal DNA might be seen in prokaryotes for the horizontal transfer of gene.
Chromosome and packaging proteins work together in eukaryotes so that chromosome does not end up tangled. As chromosome are huge, they wont fit in the nucleus, thus they are condensed by chromatin fibers to form a structure called chromatin.
In the mitochondria and chloroplast, chromosomes would also be found. In different cell cycle stages the chromosome structure might vary, such as coiled, uncoiled, replicating, dividing and etc. There are a pair of 23 chromosomes, in which one pair are the sex chromosomes called allosomes. The remaining 22 are body chromosomes called autosomes.
All the genetic information about the cell is encoded within the chromosomes. Variation is seen due to crossing over take place while reproduction. Due to mutations, various chromosomal abnormalities would be seen leading to severe conditions.
After the chromosomes get duplicated, it consist of two identical parts called the chromatid. After the uncoiling of chromosome, chromatids are formed. Within the center of the chromatid lies the centromere and are less condensed.
These are called as sister chromatids. When two chromatid exchange the genetic information with the help of chiasmata, it forms non-sister chromatid. Only during the cell division, chromatids are found as later they will again separate to form chromosomes and thus are present for a short period of time.
Although chromatids are homozygous, they can be heterozygous due to mutation. They play a role in meiosis during the prophase for genetic information exchange through chiasmata, thus ensuring variation to be seen. Protein forming is not possible by chromatids.
Chromosomes vs Chromatids
From the chromosome forms the chromatid which are identical and have a temporary role to play. Chromosomes are extremely thin made up of proteins, DNA which contains genetic information. Chromosomes can be single as well as double stranded, whereas chromatids are double stranded.
Chromatids are less condensed and Chromosomes are quite condensed. Chromatids are homozygous whereas, chromosomes are non-identical. In structure chromatids possess a long structure made up of fiber. Chromatids have ribbon like structure. DNA found in chromatid is freely moving, whereas in chromosome is tightly packed.
Chromatids are temporary structures only present during cell division while the chromosomes are present for always. Centromere is found in chromatids, while it is lacking in Chromosomes.
Chromosomes can replicate independently while the Chromatids cannot replicate as well as duplicate. Protein synthesis cannot be carried out by chromatids and is done by chromosome. Functions of chromatids are to keep a check on the cell number after the division has taken place. The transfer of genetic material from one generation to the other is the function of the chromosomes.
Chromosomes vs Chromatids Citations
- Separating sister chromatids. Trends Biochem Sci . 1999 Mar;24(3):98-104.
- Epigenetically distinct sister chromatids and asymmetric generation of tumor initiating cells. Cell Cycle . 2018;17(18):2221-2229.
- Chromosomics: Bridging the Gap between Genomes and Chromosomes. Genes (Basel) . 2019 Aug 20;10(8):627.