DNA Flashcards
Outline how Cisplatin binds to DNA strands and prevents DNA replication in cancer cells,.
Coordinate bond formed between platinum atom and lone pair on nitrogen atom of two guanine molecules. Cis-platin passes through cell membrane. Ligand exchange occurs. chlorine atoms replaced by water molecules. This occurs via a ligand substitution reaction.
Ligand exchange occurs
This stops the DNA double helix from unwinding as the shape is distorted and being copied properly which means it cant replicate.
What are the disadvantages of using cisplatin as an anticancer drug ?
Can bind to healthy cells and stop them replicating. This is a problem for cells that replicate frequently such as hair and blood cells and can lead to hair loss and a suppressed immune system
Despite the side effects of cis-platin why is it still used as a chemotherapy drug ?
this is because the balance of the long-term positive effects outweigh the negative short-term effects
How can side effects of cisplatin be lessened ?
use in small doses
target the tumour directly
What are the 3 components of a DNA nucleotide ?
2-deoxyribose sugar
Phosphate
nitrogenous base
What is the structure of DNA ?
two polynucleotide chains that are twisted together to form a double helix
the two polynucleotide chains run antiparallel to each other and are held together by hydrogen bonds between complimentary bases
what type of reaction do nucleotides join together by ? what type of bond is formed ?
Condensation reaction
phosphodiester bonds
What are the complimentary base pairing rules ?
Adenine always pairs with Thymine
Cytosine always pairs with Guanine
How many hydrogen bonds form between A and T ?
two
How many hydrogen bonds form between C and G ?
three
Why is there complimentary base pairs ?
other combinations would not line up properly, or the partial charges would repel
In order to draw out hydrogen bonds between A and T. which base is drawn on the left ?
T
In order to draw out hydrogen bonds between C and G. which base is drawn on the left ?
C
Explain complimentary base pairing in DNA
Adenine and thymine are both able to form 2 hydrogen bonds while cytosine and guanine are both able to form 3 hydrogen bonds.
As a result, adenine always bonds with thymine and guanine always bonds with cytosine resulting in complimentary DNA base pairing
In a cell, two DNA strands twist into a double helix so that the complimentary base pairs are in the right alignment to form hydrogen bonds.
