genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...

, dyad symmetry refers to two areas of a DNA strand whose base pair sequences are

inverted repeat An inverted repeat (or IR) is a single stranded sequence of nucleotides followed downstream by its complementarity (molecular biology), reverse complement. The intervening sequence of nucleotides between the initial sequence and the reverse compleme ...

s of each other. They are often described as

palindromes A palindrome is a word, number, phrase, or other sequence of symbols that reads the same backwards as forwards, such as the words ''madam'' or ''racecar'', the date and time ''11/11/11 11:11,'' and the sentence: "A man, a plan, a canal – Panam ...

. For example, the following shows dyad symmetry between sequences GAATAC and GTATTC which are reverse complements of each other. ...GAATAC...CTG...GTATTC...

Involvement in transcription

Since the two reverse complementary sequences will fold and base-pair with each other, the sequence of bases between them form a

hairpin loop Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence wh ...

. This structure is thought to destabilize the binding of

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...

enzyme to DNA (hence terminating

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, the fir ...

). Dyad symmetry is known to have a role in the rho independent method of transcription termination in '' E. coli''. Regions of dyad symmetry in the DNA sequence stall the RNA polymerase

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

as it transcribes them.

Involvement in prophage integration

Temperate

bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bacteri ...

s integrate into the host

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...

at specific interrupted dyad symmetry sequences using the phage encoded enzyme integrase (see prophage integration).Richard Calendar (2006) ''The Bacteriophages'' (Oxford University Press, Oxford, NY) , page 67

References

External links

Definition
at Biology Online Molecular genetics {{genetics-stub