DNA and Genetics

A cistron is defined as the segment of DNA that contains the complete genetic information required to synthesize one polypeptide chain or functional RNA. Muton is the smallest mutable unit, recon is the smallest recombinable unit, and operon is a cluster of functionally related genes.

It is a DNA sequence (cis-regulatory element) found in the promoter region of genes in archaea and eukaryotes.

During eclipse period, phage can be recovered by disrupting the infected bacterium.

T5 phages do not have contractile sheath.

Delayed early genes code for 5-hydroxymethylcytosine, which destroys precursors of cytosine deoxynucleotides, so that no more bacterial cytosine will be incorporated into phage DNA.

Phage phi6 infects Pseudomonas phaseolicola.

Terminal redundancy is exhibited by bacteriophage T4 DNA. 

Site specific recombination takes place between bacteriophage lambda and E.coli DNA.

Topoisomerases regulates the overwinding or underwinding of DNA. The winding problem of DNA arises due to the intertwined nature of its double-helical structure.

Each Okazaki fragment is preceded by an RNA primer, which is displaced by the procession of the next Okazaki fragment during synthesis.

A housekeeping gene is typically a constitutive gene that is transcribed at a relatively constant level. The housekeeping gene's products are typically needed for maintenance of the cell. It is generally assumed that their expression is unaffected by experimental conditions.

In this method the fragments are amplified upon primers attached to a solid surface and form DNA colonies, or DNA clusters. This method is used in the Illumina Genome Analyser sequencers.

Viruses can convert proto-oncogenes into oncogenes through several mechanisms: by introducing viral oncogenes (v-onc) that are homologous to cellular proto-oncogenes, by inserting near proto-oncogenes and causing their overexpression, or by carrying mutated versions. While radiation can also cause this conversion, viruses are particularly efficient at it.

Genetic material of organism is deoxyribonucleic acid or DNA. In order to cut the DNA with restriction enzymes, it needs to be in pure form, free from other macromolecules. Since the DNA is enclosed within the membranes, we have to break the cell open to release DNA along with other macromolecules such as RNA, proteins, polysaccharides and also lipids. This can be achieved by treating the bacterial cells/plant or animal tissues with enzymes such as lysozyme, cellulase and chitinase. Hence, lysozyme and cellulase enzymes are used in the isolation of the genetic material.

In the year 1963, the two enzymes, restriction exonuclease and restriction endonuclease, responsible for restricting the growth of bacteriophage in Escherichia coli were isolated. One of these enzyme (exonuclease) added methyl groups to DNA, while the other cut DNA (endonuclease). Restriction exonuclease removes nucleotides from the ends of the DNA, whereas restriction endonuclease makes cuttings at specific positions within the DNA.