The genomic content of the nucleus is constant for a given species where as the extra chromosomal DNA is found to be variable among the members of a population . Explain .
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⭐. The total number of genes present in a haploid set of chromosomes of a living cell is called genome.
⭐. This indicates that the genetic material or genomic content of the nucleus is constant for a given species , as the chromosomal number is constant .
⭐. The DNA present in mitochondria , chloroplasts is called extrachromosomal DNA .
⭐. This extra chromosomal DNA is variable among the members of same species .
⭐. They exist independently in the cytoplasm.
⭐. These plasmids can render bacteria drug resistance.
⭐. This extra chromosomal DNA is also not constant among the members of the same species.
Answer:
1) Genomic DNA is constant for all the individual of a species but not extra Genomic DNA .
2) Extra-Genomic DNA is present in organelles like chloroplast and mitochondria in Eukaryotic cells . It's content varies as the number of chloroplast and mitochondria variable .
3) In young cells , Mitochondria are more in number . So , young cells have more amount of extra-Genomic DNA .
Genomic DNA :-
1) DNA present in the nucleus of the cell is Genomic DNA in Eukaryotes , in different individuals of same species or in different cells of same organism , Genomic DNA content of the nucleus is constant .
2) For example , Genomic DNA content of any body cell of human or different Human beings is organised by the same number of chromosomes i.e., 46 because all the individuals belonging to the same species called Homosapien .
3) In the same individual of Homosapien , in different body cells , number of mitochondria variable depending on the rate of physiological activities .
4) Thus extra Genomic DNA content varies from cell to cell in the same organism and in different individuals .
5) In Animals , DNA that is present in the mitochondria is called extra-Genomic DNA .
6) In Eukaryotic autotrophic plants , DNA present in the chloroplast and mitochondria is Extra Genomic DNA , Genomic DNA is Nuclear DNA .
7) In the plant cells , in different individuals of same species , Genomic DNA is constant , for example , in Allium cepa , Genomic DNA content i.e., in nucleus (2n) is organised by 16 chromosomes (2n) Which is constant in the all the cells of the same plant and different plants of same species . But Allium Cepa's Extra Genomic DNA content will the varying depending on the number of chloroplast and mitochondria which are variable from cell to cell of the same plant and different plants . So , Extra Genomic DNA is not constant in the cells of same plant and different plants .
8) Genomic DNA is all the bacteria of same species will be same ( single circular naked chromosome (DNA) .
9) In Bacteria species usually plasmid which is extra genomic DNA present .
10) In some Bacteria of same species plasmids are absent . Therefore in Bacteria species also genomic DNA is constant but not extragenomic DNA .
Example :- E.Coli