nucleic acids

nucleic acid 

polymers made up of nucleotides 

nucleotide

monomer made up of one pentose sugar , phosphate group and nitrogenous base

what is the pentose sugar in RNA

ribose 

what is the pentose sugar in DNA

deoxyribose

pyrimidines

single ring structure

cytosine thymine uracil 

purines 

double ring structure 

adenine guanine

phosphodiester bond

form between adjacent nucleotides in the same strand to form sugar phosphate backbone 

how are phosphodiester bonds formed ?

condensation reaction between:

- OH group on carbon 3

- OH on phosphate group  of adjacent nucleotide

what’s this ?

adenine 

what’s this ?

guanine

what’s this ?

cytosine

what’s this ?

uracil

what’s this ?

thymine

structure of DNA ?

double-stranded

consists of 2 anti-parallel strands held tg by hydrogen bonds between complementary bases

a pyrimidine always pairs with a purine

Hydrogen bonds form between deoxyribose molecules causing the 2 DNA strands to coil up into a double helix

whats the method for DNA extraction ? (strawberries)

grind a strawberry to a fine pulp using a pestle and mortar

add lysis buffer(detergent, NaCl, protease) and mix again for at least 10s

filter the liquid into a test tube and stand for at least 10 mins

tilt the test tube and gently pour in ice cold ethanol

a white layer of DNA forms between the sample and ethanol

extract the white layer carefully using a glass rod

what is lysis buffer made of ?

detergent NaCl(salt) and protease enzyme

whats the purpose of detergent in the DNA extraction practical ?

disrupts the membrane

why do we grind the strawberries ?

to mechanically disrupt the cell wall 

whats the purpose of protease in the DNA extraction practical ?

digests histones

whats the purpose of the Na+ in the DNA extraction practical ?

decreases the solubility of DNA

whats the purpose of ethanol in the DNA extraction practical?

required to precipitate DNA as its soluble in water but insoluble in ethanol

whats the role of DNA polymerase in cells

catalyses the formation of phosphodiester bonds between nucleotides

whats the role of helicase in cells ?

unwinds and unzips the DNA double helix