Lecture 8: Nucleic Acids Flashcards
What are the 3 parts of a nucleotide?
Nitrogenous base
Pentose sugar
Phosphate groups
Two types of nitrogenous bases
Purines
Pyrimidines
What type of bond links the nitrogenous base to the pentose sugar?
N-B-glycosyl bond
Purines
have two rings
A and G are purines
Pyrimidines
have one ring
C and T are pyrimidines
How many hydrogen bonds can GC pairs make?
3 hydrogen bonds
How many hydrogen bonds can AT pairs make?
2 hydrogen bonds
Characteristics of nitrogenous bases
weakly basic and hydrophobic
move inside the DNA molecule since hydrophobic
nitrogenous bases can tautomerize which is a potential problem
Difference between ribonucleotides and nucleotides?
ribonucleotides have an -OH group at the 2; position on the pentose sugar
How many phosphate groups do nucleotides have?
can vary
can have mono-, di-, or tri-
2,3-cyclic monophosphate derivative
has phosphate in a cyclic structure at bottom of pentose sugar
Forms by ribonucleotide 2’ -OH group attacking the phosphate group to hydrolyze a phosphodiester bond
when add water can get either 2’ or 3’ phosphate
When labeling sugars what is always 1’?
where the nitrogenous base is attached
Phosphodiester linkage
5’ Phosphate attaches itself to 3’ pentose sugar on another nucleotide
5’ end
has an unliked phosphate group
3’ end
has an unliked 3’ OH
Why is DNA more stable than RNA?
The 2’ -OH of RNA makes it easily hydrolyzable in alkaline conditions
Characteristics of DNA double helix
antiparallel and right-handed
has major and minor grooves
hydrophobic core on inner column
negatively charged phosphorous backbone
A form of double helix
right-handed but doesn’t have major and minor grooves
Z form of double helix
left-handed helix
B form of double helix
true form of double helix
right-handed and has major and minor grooves
Palindrome sequence
in DNA, looks the same if we read the sequences backwards or forwards
palindromes can form different shaped structures such as a cruciform
Mirror repeat
sequence that is flipped and repeated on the same side of the strand
RNA sequence
RNA is said to be single stranded
has many complementary sequences that can base pair with its self through intramolecular pairing
RNA has no 1 simple secondary structure
How can DNA denature?
break down H-bonds through heat or changes in pH