Molecular Genetics and Gene Regulation

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.

Gene targeting can be permanent or conditional. Conditions can be a specific time during development or life of the organism or limitation to a specific tissue.

A back mutation or reversion is a point mutation that restores the original sequence and hence the original phenotype.

A DNA microarray is a collection of microscopic DNA spots attached to a solid surface. Scientists use DNA microarrays to measure the expression levels of large numbers of genes simultaneously or to genotype multiple regions of a genome.

A frameshift mutation is a genetic mutation caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that is not divisible by three. Due to the triplet nature of gene expression by codons, the insertion or deletion can change the reading frame.

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

A Robertsonian translocation in balanced form results in no excess or deficit of genetic material and causes no health difficulties. In unbalanced forms, Robertsonian translocations cause chromosomal deletions or addition and result in syndromes of multiple malformations, including trisomy 13 (Patau syndrome) and trisomy 21 (Down syndrome).

SMRT sequencing is based on the sequencing by synthesis approach. The DNA is synthesised in zero-mode wave-guides.

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

An inducible gene is a gene whose expression is either susceptible to environmental change or dependent on the position in the cell cycle.

In squamous cell carcinoma, a protein from the epidermal growth factor receptor (EGFR) gene is often overexpressed in conjunction with polysomy of chromosome 7, so chromosome 7 can be used to predict the presence of EGFR in squamous cell carcinoma.

Many noncoding DNA sequences have important biological functions as indicated by comparative genomics studies that report some regions of noncoding DNA that are highly conserved, sometimes on time-scales representing hundreds of millions of years, implying that these noncoding regions are under strong evolutionary pressure and positive selection.

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.

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.

Turner syndrome 45, X encompasses several conditions in human females, of which monosomy X (absence of an entire sex chromosome, the Barr body) is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent or has other abnormalities.

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.