Question

Describe the difference between cis-acting and trans-acting elements. Also list whether the following elements are cis- or trans-acting:

 A) β-galactosidase

 B) Operator site

 C) LacI repressor protein

 D) Lactose

 E) Permease

 F) Promoter site

Answer 1

Cis Acting Elements

Cis-acting elements are DNA sequences in the vicinity of the structural portion of a gene, which are required for gene expression.

Cis-acting regulatory element = affects only the nucleic acid molecule on which it occurs. Usually is a DNA sequence that binds some regulatory protein.

Cis acting elements = DNA itself = same in all cells of multicellular organism = target of trans acting regulatory molecules.

Most often, signal elements act only on the intramolecular nucleotide sequence to which they are attached, and they are said to act "in cis"

Intron removal in eukaryotes involves cis-splicing.

                                   Trans Acting Elements

Trans-acting factors are usually protein factors that bind to the cis-acting sequences to control gene expression.

Trans-acting regulatory element = affects target nucleic sequences anywhere in the cell. The regulatory sequence codes for a regulatory molecule -- usually a protein -- that binds to a target -- usually a DNA sequence.

Trans acting regulatory molecules = product of DNA = TF's & other molecules = different in different cell types and at different times.

Protein factors capable of acting upon otherintermolecular genome segments are called "trans-acting factors".

which is primarily found in protozoans and in lower invertebrates such as nematodes.

                                   The Following Are The Cis And Trans Acting Elements

A) Beta galactoside- Trans

B) Operator site- Trans

C) Lacl repressor protein- Cis

D) Lactose- Cis

E) Permease- Trans

F) Promoter site- Cis