Question

What three types of ends can be generated through DNA cleavage by restriction endonucleases?

Short answer

Answer: The three types of ends generated when DNA is cleaved by restriction endonucleases are blunt ends, 5' overhangs, and 3' overhangs.

Step-by-step solution

Introduce Restriction Endonucleases

Restriction endonucleases are enzymes that recognize specific DNA sequences and cleave the DNA at or near these sequences. These enzymes play a crucial role in molecular biology and genetic engineering, where they allow scientists to manipulate and analyze DNA.

Enumerate the Three Types of Ends Generated by DNA Cleavage

When restriction endonucleases cleave DNA, they generate three different types of ends: blunt ends, 5' overhangs, and 3' overhangs. Let's now take a closer look at each of these types of ends.

Describe Blunt Ends

Blunt ends are generated when the restriction endonuclease cleaves both strands of the DNA molecule at the same position, creating a "square" cut at the end of the DNA. This type of end has no overhanging DNA fragments and can be joined to any other blunt-ended DNA fragments. Examples of restriction enzymes that generate blunt ends include SmaI and EcoRV.

Describe 5' Overhangs

5' overhangs are generated when the restriction endonuclease cleaves one strand of the DNA closer to the 5' end, leaving an exposed single-stranded region on the 5' end of the other DNA strand. This type of DNA end is sometimes called a "sticky end," as it can easily hybridize with a complementary 3' overhang on another DNA fragment. Examples of restriction enzymes that generate 5' overhangs include BamHI and EcoRI.

Describe 3' Overhangs

3' overhangs are generated when the restriction endonuclease cleaves one strand of the DNA closer to the 3' end, leaving an exposed single-stranded region on the 3' end of the other DNA strand. This type of DNA end is also called a "sticky end," as it can form hydrogen bonds with a complementary 5' overhang on another DNA fragment. Examples of restriction enzymes that generate 3' overhangs include KpnI and PstI. In conclusion, the three types of ends generated through DNA cleavage by restriction endonucleases are blunt ends, 5' overhangs, and 3' overhangs. These different types of ends allow for the versatile use of restriction enzymes in DNA manipulation and molecular cloning.