Restriction Modification System

Question 1

what is DNA modification?

Answer 1

the process by which the nitrogenous bases of DNA molecule are chemically modified

Question 2

at which positions can DNA bases be methylated?

Answer 2

• m5C 5’ carbon of cytosine to 5-methylcytosin
• m4C 4’ nitrogen of cytosine to N4 methylcytosine
• m6A 6’ nitrogen of adenine to N6 methyladenine

Question 3

what enzymes transfer methyl groups to DNA bases

Answer 3

DNA methylases

Question 4

what do DNA methylases use as methyl donor?

Answer 4

s adenosylmethionine SAM

Question 5

when does the methylase reaction of bases occur?

Answer 5

post replication immediately after DNA replicated

Question 6

what position in the DNA sequence does methylation occur?

Answer 6

at DNA motifs, recurring sequence patterns

Question 7

what are the types of DNA motif?

Answer 7

palindrome, quasi palindrome. spaced dyad (symmetric or asymmetric)

Question 8

what sequence results in a double strand methylation?

Answer 8

palindrome sequences

Question 9

what are restriction endonucleases?

Answer 9

enzymes that recognise specific DNA motifs and cut DNA at a defined base position

Question 10

what is the biological defense system in bacteria?

Answer 10

restriction endonucleases and methylases