Jumping Gene, Epigenetics

Jumping Gene, Epigenetics

Q. 1

Jumping gene is –

 A

Transposon

 B

Episome

 C

Cosmid

 D

Plasmid

Q. 1

Jumping gene is –

 A

Transposon

 B

Episome

 C

Cosmid

 D

Plasmid

Ans. A

Explanation:

Ans. is ‘a’ i.e., Transposon

Transposon

.   Also known as jumping genes.

.   Transposon is a segment of DNA with one or more genes in the centre.

. It has ability to move around in a ‘cut-and-paste’ manner between chromosomal and extrachromosomal DNA.

.  Transposons attach at certain regions of chromosomal, plasmid or phage DNA.

.  Insertion of a transposon leads to the acquisition of new characteristics by the recipient DNA molecules.

.  Unlike plasmid, transposons are not self replicating, and depend on chromosomal or plasmid DNA for replication. Plasmid

. Plasmids are circular DNA molecules present in cytoplasm (extrachromosomal) of bacteria, capable of independent replication.

Episome

. When plasmid DNA is integrated into the host chromosome, it is known as episome.


Q. 2

Methylation of cytosine leads to:

 A

Increased expression of gene

 B

Decreased expression of gene

 C

No effect on gene expression

 D

Mutation

Q. 2

Methylation of cytosine leads to:

 A

Increased expression of gene

 B

Decreased expression of gene

 C

No effect on gene expression

 D

Mutation

Ans. B

Explanation:

Ans. b. Decreased expression of gene

  • “There is evidence that the methylation of deoxycytidine residues, 5MeC, (in the sequence 5′-meCpG-3) in DNA may effect changes in chromatin so as to preclude its active transcription. 
  • Acute demethylation of 5MeC residues in specific regions of steroid hormone-inducible genes have been associated with an increased rate of transcription of the gene. – Harper ‘s 29/e p421
  • “DNA methylation at the 5 position of cytosine has the specific effect of reducing gene expression and has been found in every vertebrate examined

Methylation of Cytosine

  • There is evidence that the methylation of deoxycytidine residues, 5MeC, (in the sequence 5′-meCpG-3′) in DNA may effect changes in chromatin so as to preclude its active transcription.
  • Acute demethylation of 5MeC residues in specific regions of steroid hormone-inducible genes has been associated with an increased rate of transcription of the gene.
  • However, it is not yet possible to generalize that methylated DNA is transcriptionally inactive, that all inactive chromatin is methylated, or that active DNA is not methylated.

Quiz In Between



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