DNA Flashcards
What are the 3 components of nucleotides?
A pentose sugar (either ribose or deoxyribose) a phosphate group and an organic base
What are the 2 types of nucleic acids?
RNA and DNA
Where is the 5’ and 3’ located?
5’ is next to the phosphate group and the 3’ is next to the sugar
How many hydrogen bonds link guanine and cytosine?
3
How many hydrogen bonds link adenine and thymine?
2
What 2 categories can nitrogen bases be placed into?
Purines and pyrimidines
What bases is categorised into purine?
Adenine and guanine
What bases are categorised into pyrimidines?
Cytosine, thymine and uracil
What is the structure of purine?
Double ringed structure, always pairs up with pyrimidines
What is the structure of pyrimidines?
Single ringed structure, always pair up with purine
What’s a phosphodiester bond?
A bond between a sugar and a phosphate group
What enzyme separates the 2 DNA strands?
DNA helicase
How does helicase separate the strands?
Break the hydrogen bonds
How is a template DNA primer made?
Primase makes a piece of RNA called a primer which acts as a starting point
What enzyme matches complementary base pairs to the primer?
DNA polymerase
In what direction does DNA polymerase add DNA bases?
From the 5’ to 3’ direction
Why can’t the lagging strand be made simultaneously as the other strand?
Runs from 3’ to 5’ direction, so DNA polymerase can only make the strand in small chunks
What are the small chunks of DNA bases called on the lagging stand?
Okazaki fragments
What happens to the lagging strand after the okazaki fragments are made?
Primase forms a RNA template called a primer, DNA polymerase forms a short row of DNA bases from 5’ to 3’ direction
What enzyme removes RNA primers from the DNA strands?
Exonuclease removes all RNA primers and DNA polymerase fills this gap
What enzyme seals the fragments of DNA at the very end?
DNA ligase
What is the semi-conservative model?
The parental DNA strands separates each one is present in each daughter molecule. One strand of new DNA one strand of original DNA
What is the conservative model?
One daughter molecule contains both parental DNA strands the other molecules contains both new DNA strands
What is the dispersive model?
The parental DNA is broken down into double stranded segments. The segments reassemble, each individual strand is a patchwork of original and new DNA
What model did Stahl support?
Semi-conservative model
What model did Meselsohn support?
Conservative model
What experiment did Stahl and Meselsohn carry out?
Grew DNA in a E.coli culture containing nitrogen-14 and nitrogen-15. the resulting DNA had one strand nitrogen-14 and the other nitrogen-15, demonstrating semi-conservative replication
What joins the nucleotides of the new strands together?
Condensation reactions
