Nucleotides And Nucleic Acid Flashcards
What are nucleotides made up of?
• Pentose sugar (in the centre)
• Nitrogenous base
• Phosphate group (negatively charged)
Which elements do nucleotides contain?
CHONP
What is the difference between pentose sugars in DNA and RNA?
In DNA, it’s deoxyribose. In RNA, it’s ribose.
What are the four bases found in DNA?
• Adenine (A)
• Thymine (T)
• Guanine (G)
• Cytosine (C)
Which bases have a double-ring structure (purines)?
Adenine and guanine (think ADD a ring)
Which bases have a single-ring structure (pyrimidines)?
Thymine and cytosine
Which base found in DNA is not found in RNA?
Thymine
What are the four bases found in RNA?
Adenine, uracil, guanine and cytosine
How are polynucleotides formed?
The phosphate group and the hydroxyl group (on carbon 3 of the pentose sugar) of another nucleotide join together to form a phosphodiester bond.
What is the bond between two nucleotides called?
Phosphodiester bond
What makes up the backbone of DNA?
Sugar-phosphate (pentose sugar joined to phosphate group)
What bonds occur between opposite strands of bases?
Hydrogen bonds
What does guanine always pair with?
Cytosine
What does adenine always pair with?
Thymine
What are the complementary base pairs?
• AT
• GC
Why is the distance between bases constant the whole length of the DNA molecule?
Because pyrimidines always pair with purines
How many hydrogen bonds do guanine and cytosine form?
Three
How many bonds do adenine and thymine form?
Two
What are the differences between DNA and RNA?
• DNA found in nucleus - RNA found in cytoplasm
• DNA is extremely long - RNA is relatively short
• DNA is double-stranded - RNA is single-stranded
What does DNA helicase do?
It causes the hydrogen bonds between complementary bases to break
What is the difference between normal nucleotides and activated nucleotides?
Activated nucleotides have three phosphate groups
What does DNA polymerase do?
Catalyses the formation of phosphodiester bonds between activated nucleotides
When do the activated nucleotides lose their extra two phosphate groups?
When the phosphodiester bonds reform
What is semi-conservative replication?
When the original DNA splits into two strands, and then each strand is then replicated into a complementary new strand
