[Unit 2.1] | Structure Of RNA And DNA Flashcards
What are the constituents of a nucleotide?
• Phosphate group
• Pentose sugar (Ribose in RNA, Deoxyribose in DNA)
• Nitrogenous base
What complementary base pairs exist in nucleotides and how are they paired?
• Adenine + Thymine (Uracil in RNA)
• Paired with 2 hydrogen bonds.
• Cytosine + Guanine
• Paired with 3 hydrogen bonds.
What is the key property of a purine base and which 2 bases are purines?
• Purines are double ringed & pair with pyrimidines.
• Adenine & Guanine.
• “Pure like silver (Ag)”
What is the key property of a pyrimidine base and which 3 bases are pyrimidine?
•Pyrimidines are single ringed and pair with purine bases.
• Cytosine, Uracil, Thymine
• “Pyramids are pointy and can CUT you.”
What reaction causes the formation of polynucleotides, and what bond exists between the mononucleotides?
• Condensation reaction. (in the presence of DNA polymerase.)
• Phosphodiester bonds. (Covalent.)
• What is significant about phosphodiester bonds being strong covalent bonds?
• It ensures the genetic code’s sequence does not break down…
• Thereby preventing the creation of potentially mutated proteins being created.
What is the function of DNA?
• It stores the genetic code for sequences of amino acids that make up proteins.
• Passes on the code to new generations of cells.
• (Each codon, which consists of 3 base pairs, codes for one amino acid.)
Why is DNA good for carrying information? (6 reasons)
> Structure:
• Very large molecule to carry lots of information.
• Bases can be arranged to form thousands of combinations.
• Phosphodiester bonds and double helix structure provides stability & protects the vulnerable base pairs.
> Replication:
• Complementary base pairs make exact copying possible during DNA replication.
• Weak hydrogen bonds allow the strands to be unzipped during DNA replication.
• Double stranded so each strand can be used as a template during DNA replication.
What does Chargaff’s data suggest about the 4 nitrogenous bases?
There is always the same ratio of A:T and G:C within DNA.
List the differences of the structure of DNA & RNA. (5 differences)
• DNA: Adenine + Thymine
RNA: Adenine + Uracil
• DNA: Deoxyribose Sugar
RNA: Ribose Sugar
• DNA: Double stranded
RNA: (Usually) Single stranded
• DNA: Arranged in a double helix
RNA: No helix structure
• DNA: Long
RNA: Relatively short
What are the 3 main types of RNA?
• Ribosomal RNA (rRNA)
• Transfer RNA (tRNA)
• Messenger RNA (mRNA)
Describe the features of rRNA. (2)
• Makes up the bulk of the ribosome structure.
• Combines with other proteins to form ribosomes.
Describe the features of tRNA. (4)
• Found exclusively in the cytoplasm.
• Secondary structure shaped like a clover leaf.
• Transfers 1 of 20 amino acids to a ribosome during protein synthesis.
• The 3 bases found at the amino acid attachment site complement the 3 bases on mRNA.
• (The amino acids that are transferred come from mRNA.)
Describe the features of mRNA. (3)
• Made in the nucleus when free RNA nucleotides pair with DNA templates.
• mRNA pairs Uracil (instead of Thymine) with Adenine.
• mRNA is a copy of a gene from DNA.
