Structure of DNA and RNA Flashcards
What are nucleic acids?
Nucleic acids are the genetic material of the cell and are composed of recurring monomers called nucleotides
What are nucleotides made out of?
Nucleotides consist of three parts:
- 5-carbon pentose sugar
- Phosphate group
- Nitrogenous base
What is DNA?
Deoxyribonucleic acid (DNA) is a stable double stranded form of nucleic acids that stores the genetic information for cells
What is RNA?
Ribonucleic acid (RNA) is a more versatile, single stranded form of nucleic acids that transfers the genetic information for decoding
What are the 3 differences between DNA and RNA?
- Sugar type
- DNA is made out of deoxyribose
- RNA is made out of ribose - Number of strands
- DNA is double stranded (forms a double helix)
- RNA is single stranded - Base composition
- four bases for DNA: adenine, cytosine, guanine, and thymine
- four bases for RNA: adenine, cytosine, guanine, and uracil
What is the nature of the bonding between two nucleotides?
The phosphate group of one nucleotide attaches to the sugar of another nucleotide (at the 3’ hydroxyl group) of the adjacent nucleotide. This is a covalent bond, known as the phosphodiester bond.
What is the role of hydrogen bonding in DNA?
Hydrogen bonding between complementary nitrogenous bases holds together the two polynucleotide chains that make up DNA, thereby forming a double helix.
What are the complementary bases in DNA?
- Adenine - Thymine
2. Guanine - Cytosine
Why are the two strands of DNA antiparallel?
In order for the bases to be facing each other, and thus able to pair, the strands must be running in opposite direction.
- One strand is oriented in the 5’ to 3’ direction and the other is oriented in the 3’ to 5’ direction
Who proposed the structural organisation of DNA molecules?
James Watson and Francis Crick in 1953, after trial and error and model making, proposed the model of DNA:
- DNA strands are anti parallel and form a double helix
- DNA strands pair via complementary base pairings
- Outer edges of bases remain exposed (allows access to replicative and transcriptional proteins)
Who is Rosalind Franklin?
The final construction of a correct DNA molecule owed heavily to the X-ray crystallography data generated by Rosalind Franklin, which confirmed that the arrangement of the DNA strands was helical.
