Long terminal repeats

Long terminal repeats (LTRs) are sequences of DNA that repeat hundreds or thousands of times. They are found in retroviral DNA and in retrotransposons, flanking functional genes. They are used by viruses to control of gene expression and integration. For example, a retrovirus genome might contain the following features:

LTR -- gag -- pol -- env -- LTR

The LTRs are partially transcribed into an RNA intermediate, followed by reverse transcription into complementary DNA (cDNA) and ultimately dsDNA (double-stranded DNA) with full LTRs. The LTRs then mediate integration of the retroviral DNA via an LTR specific integrase into another region of the host chromosome. Retroviruses such as Human Immunodeficiency Virus (HIV) use this basic mechanism.

quiz

1 Long terminal repeats (LTRs) are sequences of DNA that ________ hundreds or thousands of times.

	repeat
	repeats
	repeating
	repeated

2 They are found in retroviral DNA and in retrotransposons, ________ functional genes.

	finding
	finds
	flanking
	flanked

3 They are used by viruses to ________ of gene expression and integration.

	control
	take control
	taking control
	took control

4 The LTRs are partially transcribed into an RNA intermediate, followed by reverse transcription into complementary DNA (cDNA) and ultimately dsDNA (double-stranded DNA) with full ________.

	LTR
	LTRs
	LTR's
	LTRing

5 The LTRs then mediate integration of the retroviral DNA via an LTR specific ________ into another region of the host chromosome.

	integrase
	integrases
	integrase
	integrating

6 Retroviruses such as Human Immunodeficiency Virus (HIV) ________ this basic mechanism.

	use
	use
	uses
	using