Nucleic Acids and DNA Replication Flashcards
What are nucleotides?
The monomers that make up polynucleotides (DNA & RNA).
What is DNA made up of?
- Deoxyribose (Pentose sugar).
- Phosphate.
- Nitrogen containing base (Adenine, thymine, cytosine, guanine).
What is RNA made up of?
- Ribose (pentose sugar).
- Phosphate.
- Nitrogen containing base (Adenine, guanine, cytosine and uracil).
What does DNA stand for?
Deoxyribonucleic acid.
What does RNA stand for?
Ribonucleic acid.
What features does DNA have?
- Double stranded (double helix).
- Long polymer/polynucleotide.
- Carries the genetic information which codes for proteins.
What features does RNA have?
- Single stranded.
- Short polynucleotides.
- Transfer genetic code from DNA (nucleus) to ribosomes in the cytoplasm.
- Ribosome formed from RNA and proteins.
What type of bond forms between nucleotides?
Phosphodiester bonds.
What does adenine pair with?
Thymine (DNA) or Uracil (RNA).
What does guanine pair with?
Cytosine.
what is the structure of polynucleotides?
- Sugar-phosphate backbone.
- Hydrogen bonds between antiparallel strands.
What method if widely accepted as the method for DNA replication?
Semi-conservative DNA replication.
What are the stages of semi-conservative DNA replication?
1) DNA helices unwinds DNA by breaking the H-bonds.
2) Both strands act as templates.
3) Free DNA nucleotides attach by complementary base pairing.
4) DNA polymerase joins nucleotides, forming phosphodiester bonds.
5) H-bonds reform.
Why is DNA replication referred to as semi-conservative?
The new DNA contains one new strand and one original strand.
How did Meselson and Stakl prove DNA replication is semi-conservative?
- Population cultured in a growth medium containing heavy nitrogen (15N) only (when centrifuged only one heavy band is observed).
- Cells transferred to a medium with only light nitrogen (14N).
- After one replication the DNA band was intermediate (twice the thickness).
- After two replications in light nitrogen, intermediate and light bands were observed.
- Proving DNA replication is semi-conservative.
What is the DNA antisense strand?
Template strand that acts as the template for mRNA. its complementary to genes on the sense strand.
What is the DNA sense strand?
Contains the genes and does not act as the template for mRNA.
What process forms mRNA from pre-mRNA?
Splicing.
What is pre-mRNA strand?
The same as DNA sense strand except U replaces T.
Why did many scientists doubt that DNA carried the genetic code?
Its relative simplicity.
Which scientists discovered the structure of DNA and suggested that its replication was semi-conservative?
Watson and Crick.
What does semi-conservative replication ensure?
Genetic continuity between generations of cells.
