2.1 Structure of RNA and DNA Flashcards
What are the 2 main types of nucleic acids?
- DNA
- RNA
Both DNA and RNA are the polymer of ___ .
Nucleotides
In other words, both DNA and RNA are ___ .
Polynucleotides
What are made up of a nucleotide?
- pentose sugar
- phosphate
- nitrogenous/nitrogen-containing base
What are the 5 types of nitrogenous bases?
- A - adenine
- T - thymine
- C - cytosine
- G - guanine
- U - uracil
How are the pentose sugar, phosphate and organic base joined? What is formed?
By condensation. To form a single nucleotide.
What is formed when two nucleotides are joined together by condensation?
Dinucleotide
What is formed when many nucleotides are joined together by condensation?
Polynucleotide
What bond is linked between two nucleotides?
Phosphodiester bond
What is a DNA molecule?
A double helix with two polynucleotide chains
What type of pentose sugar does a DNA nucleotide have?
Deoxyribose
What are the 4 types of nitrogenous bases can a DNA nucleotide have?
- A - adenine
- T - thymine
- C - cytosine
- G - guanine
What bond is linked between specific complementary nitrogenous base pairs?
Hydrogen bond
How are the nitrogenous bases paired?
Adenine always pairs with thymine, guanine always pairs with cytosine.
What are purines? Which 2 bases are purines?
Larger bases that contain two carbon ring structures. A and G are purines.
What are pyrimidines? Which 2 bases are pyrimidines?
Smaller bases that contain one carbon ring structure. T and C are pyrimidines.
How many hydrogen bonds are needed for adenine to pair with thymine?
2
How many hydrogen bonds are needed for cytosine to pair with guanine?
3
In what direction do the two strands of DNA run in?
Opposite direction/anti-parallel. One strand runs in the 5’ to 3’ direction and the other runs in the 3’ to 5’ direction.
What is the function of DNA?
Holds genetic information
Why is DNA a stable molecule?
- the phosphodiester backbone protects the more chemically reactive nitrogenous bases inside the double helix
- hydrogen bonds link nitrogenous base pairs forming bridges between phosphodiester uprights (立柱)
- as there are 3 hydrogen bonds between cytosine and guanine, the higher the proportion of C-G pairings, the more stable the DNA molecule
How is DNA adapted to carry out its function?
- it is a stable molecule - so it is normally passed from generation to generation without significant change
- its two separate strands are only bonded with hydrogen bonds - so it can be separated during DNA replication and protein synthesis
- it is very large - so it carries a huge amount of genetic information
- the bases are paired - so DNA can be replicated and tranfered as mRNA
- the bases are within the helical cylinder of the deoxyribose-phosphate backbone - so the genetic information can be protected
What is a RNA molecule?
A relatively short polynucleotide chain
What type of pentose sugar does a RNA nucleotide have?
Ribose
