DNA and Genetics

Primase adds RNA primers onto the lagging strand, which allows synthesis of Okazaki fragments from 5’ to 3’. However, Primase creates RNA primers at a much lower rate than that at which DNA polymerase synthesizes DNA on the leading strand.

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

The lac repressor is a tetramer of identical subunits. Each subunit contains a helix-turn-helix (HTH) motif capable of binding to DNA. The operator site where repressor binds is a DNA sequence with inverted repeat symmetry.

In positive repressible operons, the activator proteins are normally bound to the pertinent DNA segment. However, when an inhibitor is bound by the activator, it is prevented from binding the DNA. This stops activation and transcription of the system.

Promoter bashing is a technique used in molecular biology to identify how certain regions of a DNA strand, commonly promoters, affect the transcription of downstream genes.

Allolactose is an isomer of lactose and is the inducer of the lac operon. Lactose is galactose-(β1->4)-glucose, whereas allolactose is galactose-(β1->6)-glucose. Lactose is converted to allolactose by β-galactosidase in an alternative reaction to the hydrolytic one.

Helicases are proteins that are a type of a molecular motor. They use the chemical energy in nucleoside triphosphates, predominantly ATP, to break hydrogen bonds between bases and unwind the DNA double helix into single strands. These enzymes are essential for most processes where enzymes need to access the DNA bases.

It is referred to the situation in which a gene does not have a vertical origin (that is direct inheritance from parent to offspring) but comes from an unrelated genome. It is recognised that this type of transfer occurs between bacteria, and that it also has taken place between the genomes of the cell organelles like mitochondria, chloroplasts and the nuclear genomes.

The heat stable enzyme used in PCR obtained from Thermophilous aquaticus bacteria is Taq polymerase.

The polymerase chain reaction amplifies specific DNA sequences.  

The Nobel Prize for catalytic properties of RNA was awarded to Sidney Altman and Thomas Cech.

The phi X 174 bacteriophage was the first DNA-based genome to be sequenced. This work was completed by Fred Sanger and his team in 1977.

Plasmids that can be propagated in cells of two or more different species are called shuttle vectors. An expression vector is generally a plasmid that is used to introduce a specific gene into a target cell.

This option is correct because all are correctly matched. Recombinant DNA technology is a technology that combines genes from different sources into a single DNA molecule. Restriction fragments are pieces of DNA that have been cut into different lengths. A genomic library is a collection of cloned DNA pieces from a genome. Restriction enzymes are enzymes isolated from bacteria that recognise specific sequences in DNA and then cut the DNA to produce fragments, called restriction fragments. DNA fingerprinting is a method of isolating and making images of sequences of DNA.

The operon consists of a series of structural genes, a segment of DNA called operator, adjacent to the structural and next to the operator and an additional DNA segment called the promoter. Elsewhere on the chromosome there is a segment of DNA called regulator gene.