Nucleic acids Flashcards
(16 cards)
What is the basic function of DNA?
Holds the genetic information which codes for polypeptides or fully functional RNA.
What is the basic function of RNA?
Transfers genetic information from the DNA to the ribosomes.
What two molecules is rRNA made up of?
- RNA.
- Proteins.
Draw and label a DNA nucleotide.
Draw and label a RNA nucleotide.
What is the difference between a DNA nucleotide and an RNA nucleotide?
- A DNA nucleotide has a deoxyribose sugar, and a RNA nucleotide has a ribose sugar.
- DNA has thymine and RNA has uracil.
Describe how nucleotides join together to form polynucleotides.
- Nucleotides are joined together by phosphodiester bonds, formed between the phosphate group of one nucleotide and the sugar of another nucleotide, with the removal of three water molecules.
- In a condensation reaction.
Describe the structure of DNA.
- Polymer made of nucleotides.
- Each nucleotide contains a deoxyribose sugar, a phosphate group and a nitrogenous base.
- The nucleotides are joined together by phosphodiester bonds to form polynucleotide chains.
- There are two polynucleotide chains held together by hydrogen bonds, formed between complementary base pairs.
- Adenine is complementary to thymine. Cytosine is complementary to Guanine.
- Double-helix.
Describe the structure of mRNA.
- A polymer of nucleotides.
- Each nucleotide contains a ribose sugar, a phosphate group and a nitrogen-containing base.
- The bases are A, Uracil, C and G.
- Phosphodiester bonds hold adjacent nucleotides together.
- Single-standed molecule.
What is the difference between DNA and RNA?
- DNA is longer compared to RNA.
- DNA is double-stranded and RNA is single-stranded.
- DNA contains deoxyribose sugars, and RNA contains ribose sugars.
- DNA contains the base thymine, and RNA contains uracil.
- DNA has hydrogen bonding between the complementary base pairs, and RNA does not.
How does the structure of DNA relate to its function?
- It is double-stranded, meaning both strands can be used as templates for semi-conservative replication.
- The hydrogen bonds between bases are weak, so the strands can be separated easily.
- It is a long molecule, meaning it stores a lot of genetic information.
- It is a double helix, making it compact.
Describe the process of semi-conservative DNA replication.
- DNA helicase breaks the hydrogen bonds between the chains, causing the DNA to unwind.
- Both strands act as templates.
- Free DNA nucleotides are attracted to exposed bases by specific complementary base pairing.
- Hydrogen bonds form between A and T and C and G.
- DNA polymerase joins adjacent nucleotides together by forming phosphodiester bonds between them.
Why is DNA replication described as being semi-conservative?
- Each strand is used as a template to make a new strand.
- The new DNA molecule contains one original strand and one new strand.
Why does DNA polymerase work in opposite directions along the DNA strands?
- DNA has antiparallel strands.
- This means the arrangement of nucleotides on the two ends is different.
- DNA polymerase is an enzyme with an active site that has a specific shape.
- So they can only bind to the substrate with the complementary shape.
Name the two scientists who proposed models of the chemical structure of DNA and DNA replication.
Watson and Crick
Describe the work of Meselson and Stahl in validating the Watson-Crick model
model of semi-conservative DNA replication.
- Bacteria were grown in a medium that contained heavy nitrogen. The nitrogen was incorporated into their DNA.
- When the DNA was extracted and centrifuged, it settled near the bottom. This is because all DNA contains 2 heavy chains.
- The bacteria were placed in a medium that contained light nitrogen and allowed to divide once.
- When the DNA was extracted and centrifuged, it settled near the middle. This shows that the DNA contains one new light strand and one old heavy strand.
- The bacteria were placed in a medium that contained light nitrogen and allowed to divide again.
- When the DNA was extracted, half settled in the middle, and the other half settled near the top. This shows that two DNA molecules contain one new light strand and one old heavy strand. The other two contained one old light strand and one new light strand.
