3.1.5 Nucleic acids are important information-carrying molecules Flashcards
(18 cards)
What is DNA?
Deoxyribonucleic acid is used to store/hold genetic information required for growth and development
What is RNA?
Ribonucleic acid is used to transfer genetic information from DNA to ribosomes
What is the strucutre of DNA?
Phosphate - Deoxyribose (Pentose Sugar) - Nucleotide Base
What is the strucutre of DNA?
Phosphate - Ribose (Pentose Sugar) - Nucleotide Base
What is a polynucleotide?
Many nucleotides that are joined together by a condesation reaction to form a phosphodiester bond
What is the structure of DNA?
DNA consits of a helix strucutre made of two polynucleotide strands.
What are the 4 bases in DNA?
Adenine
Cytosisne
Thymine
Guanine
What is complementary base pairing?
Two DNA polynucleotides which join together by hydrogen bonds
What are the complementary base pairs in DNA?
Adenine - Thymine (2 H-bonds)
Guanine - Cytosine (3 H-bonds)
What direction do the DNA strands occur in?
Antiparallel directions
How is RNA different to DNA?
- Ribose sugar is present instead of Deoxyribose
- Uracil base is present instead of Thymine
Who discovered DNA?
James Watson and Francis Crick
Why does DNA replicate?
For production of new cells during cell division
How does DNA replicate?
DNA replicates by Semi-Conservative Replication
What is the process of DNA replication?
- DNA Helicase breaks the hydrogen bonds between the two polymucleotide strands which causes the helix to unravel
- Each original strand then acts as a template strand so that free-floating nucleotide s are attached to their complementary base
- Condensation reactions between the phosphate group of one nucleotide and the deoxyribose sugar of the other occurs to produce a phosphodiester bond
- This condensation reaction is catalysed by the enzyme DNA polymerase
- Hydrogen bonds between the original and new strand join the two strands together
What evidence is there for Semi-conservative DNA replication?
Watson and Crick determined the structure of DNA and how its semi-conservative replication process. However the process wasn’t proved until 1958
Who discovered semi-conservative DNA replication?
Messelson and Stalh
How was semi-conservative DNA replication proved?
- Two samples of bacteria were gronw for many generations - one in N14 and the other in N15
- A sample of DNA was taken from each batch of bacteria, and spun in a centrifuge which caused N15 to settle lower than N14
- Bacteria grown in N15 was then placed in N14
- If replication was conservative, then original DNA would be higher up
- If replication was semi-conservative, then one strand of DNA would be N14 and N15 therefore settling in the middle after centrifugation
- As it turned out, the sample settled in the middle proving that DNA replication was Semi-Conservative
