nucleic acids Flashcards
What is the function of DNA?
Stores genetic information
What is the function of RNA?
Transfers genetic information from DNA to ribosomes
What are the differences between DNA and RNA
DNA nucleotides》
- pentose sugar deoxyribose
- thymine base
RNA nucleotides》
- pentose sugar ribose
- uracil base
Draw a DNA & RNA nucleotide
phosphate group
base
DNA 》 Deoxyribose
RNA 》 Ribose
What bonds are formed by condensation polymerisation of DNA / RNA nucleotides
phosphodiester bonds
Which bases are complimentary?
DNA 》 A-T C-G
RNA 》 A-U C-G
Give the full name of each base
A - Adenine
T - Thymine
U - Uracil
C - Cytosine
G - Guanine
How is the structure of DNA related to its functions?
Weak hydrogen bonds between bases 》 can be unzipped for replication
Double helix with sugar phosphate backbone 》 protects bases and hydrogen bonds
Long molecule 》 store lots of genetic information
Coiled double helix 》 compact
What is semi-conservative replication and who proved it?
- Each of the two new DNA molecules are composed of one ‘new’ and one ‘old’ strand
- Proved by Meselsohn and Stahl
Name two other types of replication?
Conservative
Dispersive
Process of DNA replication [9]
- DNA helicase breaks hydrogen bonds between bases
- unwinding the double helix
- making two strands which act as templates
- free floating DNA nucleotides attracted to exposed bases via specific complimentary base pairing
- hydrogen bonds form
- DNA polymerase joins adjacent nucleotides on a new strand by condensation
- forming phosphodiester bonds
- replication is semi-conservative
- ensures genetic continuity between generations of cells
What type of strands does DNA have?
antiparallel strands
What is DNA polymerase? [3]
- an enzyme
- can only bind to and add nucleotides to the 3’ end of the developind strand
- works in a 5’ to 3’ direction
Evidence for semi-conservative replication [9]
- Bacteria grown in nutrient solution containing heavy nitrogen (N15) for several generations
- Nitrogen incorporated into bacterial DNA bases
- Bacteria then transferred to a nutrient solution containing light nitrogen (N14)
- allowed to grow and divide twice
- DNA from different samples extracted
- spun in a centrifuge
sample 1 = 2 heavy strands
sample 2 = 1 original heavy + 1 new light strands
sample 3 = 50% of molecules contain 1 heavy + 1 light
50% of molecules contain both light
