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Difference Between Sister Chromatid and Non Sister Chromatid

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Last updated date: 13th Apr 2024
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Let Us Introduce And Explain Sister Chromatid and Non Sister Chromatid

Prior to cell division, the chromosomes in a cell's nucleus appear as strands like threads. Each chromosome's DNA molecule replicates (via DNA replication) prior to cell division, such as meiosis. Each chromosome would have two copies of DNA after DNA replication. The chromosomes condense during the first meiotic division, also known as Meiosis I. There would be a kinetochore connecting the two strands of each of these condensed chromosomes. They line up at the equatorial area during metaphase. Each condensed chromosomal strand will now be referred to as a chromatid. Either the chromatids are sister chromatids or they are not. Any one of the two chromatids of paired homologous chromosomes is referred to as a non-sister chromatid.Formation of one of the two longitudinally adjacent threads when a eukaryotic chromosome replicates before mitosis is termed as chromatid. At the centromere, the chromatids are fused together.Sister chromatids are descended from the same chromosome.

Let Us Explain Sister Chromatid and Non Sister Chromatid

Sister Chromatid

Two replicated chromatids of a chromosome are connected by a centromere to form sister chromatids. During DNA replication, sister chromatids replicate in the S phase of the interphase. Significantly, the same allele is present at the same loci in both sister chromatids. Furthermore, during mitosis and meiosis, sibling chromatids of the same chromosome act differently.


Individual chromosomes align at the cell equator during the metaphase of mitosis so that two sister chromatids disperse outside the metaphase plate or equator. The two sister chromatids then separate from one another and travel apart during anaphase after the centromere separates. The divided sister chromatids subsequently shift to opposing poles.


Non Sister Chromatid

Chromatids in each chromosome of a homologous chromosome pair are known as nonsister chromatids.  Each chromosome with a diploid (2n) chromosomal number in the genome contains a homologous chromosome. Every parent contributes a homologous chromosome to the child. Since nonsister chromatids are inherited from both parents, they are not identical.


Every chromosome has a homologous pair, one from the mother (maternal) and one from the father (paternal). These homologous pairings are known as non-sister chromatids that contain the same genes but may have different alleles at the same loci.


Let Us Understand: Difference Between Sister Chromatid And Non Sister Chromatid

S.No.

Sister Chromatid

Non Sister Chromatid

1.

Two replicated chromatids of a chromosome are connected by a centromere to form a sister chromatid.

Chromatids that are located on distinct chromosomes within a homologous chromosome pair are known as non sister chromatid

2.

Synthesize during the S phase of the interphase

Synthesize during the metaphase I of meiosis

3.

These are located on the same chromosome 

Non sister chromatid are located in a homologous chromosome pair

4.

In sister chromatids crossing over does not occur

Crossing over occur in non sister 

5.

Contain same alleles at same loci

Having different alleles of the similar gene at same loci

6.

Occur in asexual reproduction

Occur in sexual reproduction


Characteristics of  Sister Chromatid And Non Sister Chromatid

  • Sister and non-sister chromatids are both produced during DNA replication

  • They both occur in pairs

  • They both contain alleles of the same gene, sister chromatids containing the same alleles at the same loci, while non-sister chromatids contain different alleles at the same loci. 

  • They both separate from one another during cell division.


Recap: What is Sister Chromatid and Non Sister Chromatid

Two replicated chromatids of a chromosome are connected by a centromere to form sister chromatids. Chromatids in distinct chromosomes of a homologous chromosomal pair are known as non sister chromatids. The main distinction between sister and nonsister chromatids is that although nonsister chromatids contain several alleles of the same gene in the same locus, sister chromatids contain just one allele of the same gene. However, the same or different alleles of a gene are present at the same locus in both sister and nonsister chromatids. On the same chromosome, sister chromatids are located. They are hence exact replicas. Nonsister chromatids, however, are not similar because they are found in a pair of homologous chromosomes that came from different parents.

FAQs on Difference Between Sister Chromatid and Non Sister Chromatid

1. What is the difference between sister chromatid and non sister chromatid?

Sister chromatid and non sister chromatid difference is that sister chromatids are identical and have the same allele at the same loci, whereas non sister chromatids cannot be identical and have different alleles of the same gene at the same loci.

2. Why are they known to be non sister chromatid ?

Chromatids in each chromosome of a homologous chromosome pair are known as nonsister chromatids.  Each chromosome with a diploid (2n) chromosomal number in the genome contains a homologous chromosome. Every parent contributes a homologous chromosome to the child. Since nonsister chromatids are inherited from both parents, they are not identical.


Every chromosome has a homologous pair, one from the mother (maternal) and one from the father (paternal). These homologous pairings are known as non-sister chromatids that contain the same genes but may have different alleles at the same loci. They are not exact copies of each other.

3. What are homologous chromosomes?

One maternal and one paternal chromosome integrate  with one another inside a cell during the fertilization to form a pair of homologous chromosomes, also known as homologs. In loci where they offer sites along each chromosome that allow a pair of chromosomes to correctly align with one another before separating during meiosis, homologs share the same genes.