DNA Flashcards
What must all things have to be living things have?
- a metabolism:
a coordinated system of chemical reactions contributing to its maintenance system, a system that imports energy to maintain order - hereditary replication
a system of copying in which the new structure resembles the old
Describe Griffith’s experiment of transformation.
- mouse injected with S strain - dies
- mouse injected with R strain - lives
- mouse injected with heat killed S strain - lives
- mouse injected with R strain + heat killed S strain - dies
What can be concluded from Griffith’s experiment?
DNA is hereditary material
What is Chargaff’s rule?
A = T
G = C
A + T // G + C
What did Wilkins and Franklin discover?
Using X-ray diffraction they found DNA’s structure is long and thin with a helical structure.
What did Watson and Crick propose about DNA?
- could code for amino acids
- mutations could bring about significant changes
- double strands allow it to be copied easily
What are pyrimidines and purines?
Pyrimidines: Cytosine and Thymine
Purines: Guanine and Adenine
What is at the 5’ and 3’ end?
5’: a free phosphate
3’: a free sugar
What is semi conservative replication?
Each strand of the original molecule remains intact and serves as the template for the synthesis of a complementary strand.
How can all this DNA be replicated during mitosis/meiosis?
Replication occurs simultaneously at several points along the DNA strand. Replication ‘bubbles’ eventually join up.
Why does DNA need repairing?
- Mutagens can alter the structure
- Replication errors (rate of 1 per 10^5 bases in DNA polymerase replication)
Final error rate in replication is < 1 per billion nucleotides.
How?
- DNA proofreading
corrects errors during replication when the orientation of the hydroxyl group is wrong - Mismatch repair
Correction after replication, deformity in the secondary structure is recognised.
