Self Assessment Answer # 9
for Lesson 19

by Dr Jamie Love © 2002 - 2005
Genetics Course

The complement of GAATTC is GAATTC. Strange but true!

This type of DNA segment is called a palindrome, meaning that both strands have the same nucleotide sequence but in antiparallel orientation! Let's check ourselves by writing one of the sequences in the wrong direction.
5'GAATTC3'
3'CTTAAG5'

Now you can see that these two form a perfect match.

Palindromes hold a special place in the world of molecular genetics and we will return to them in subsequent lessons. For now, appreciate that they occur and have a look at these (important) palindromes.

GGCC

CCCGGG

AAGCTT

GGATCC

You don't have to write them out, but read these sequences (from right to left) as you recall each ones complement and you will see that it is the same sequence that is written (from left to right)! Cool.

Please take these "complementary sequence problems" seriously. I know they are hard but once you get the hang of it you will be able to do them quickly and with little effort. Besides, they are good practice for more advanced work that we will do where it is very important to keep track of the directionality (5' to 3') and pairs that form.

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