DNA replication - biological molecules Flashcards
what is DNA’s main use
to store genetic information
what is RNA’s main function
to transfer genetic information from DNA to the ribosomes
what occurs in the ribosomes
translation - make polypeptide chains
what is a nucleotide made from
a pentose sugar
a base made of nitrogen
a phosphate group
a nucleotide is a m—–
monomer
what monomers make up DNA and RNA
nucleotides
what is the pentose sugar in DNA called
deoxyribose
what do every DNA nucleotide have the same
sugar and phosphate group but different bases
what are the 4 different bases in DNA
adenine, cytosine, guanine or thymine.
what is the name for the sugar moelcule in RNA
ribose
what are the 4 different bases in RNA
adenine, cytosine, guanine or uracil.
which base gets replaced in RNA
T with Uracil
what is a polynucleotide
a polymer of nucleotides
what reaction forms polynucleotides
a condensation reaction
what bonds in formation of polynucleotides
phosphate group of one nucleotide and sugar of another
what bond forms in the condensation of nucleotides
phosphodiester bond
what is the sugar-phosphate backbone
the chain of sugar and phosphates formed in condensation reaction
how many chains is DNA made up of
2 polynucleotide chains
how do the chains in DNA join up
hydrogen bonding
what is complementary base pairing
each base can only join to another specific base
which bases pair with each other
A-T
C-G
how many hydrogen bonds form between A and T
2
how may hydrogen bonds form between C and G
3
how does DNA twist around
two antiparallel strands twist to form double helix
what does antiparallel mean
they run in opposite directions
what is RNA’s polynucleotide chain like
relatively short
why was DNA not believed to carry genetic code historically
its simple chemical composition
what does semi conservative DNA replication mean
in the daughter DNA one strand is from parental DNA and one is new
what does DNA helicase enzyme do
breaks the hydrogen bonds between bases
what effect will helicase have on the double helix
causes the helix to unwind to form two single strands
what does each original strand then do
acts as a template for a new strand
what effect does complementary base pairing have on free floating nucleotides
causes free floating nucleotides to be attracted to their exposed base on original template strand
what happens to adjacent nucleotides
they are joined together by a condensation reaction
what is the function of DNA polymerase
to join together adjacent nucleotides
what does each new DNA molecule contain
one strand from original DNA and one new strand
what was the first step in Meselson and stahls experiment
they grew 2 samples of bacteria one containing 14N nitrogen and one containing 15N nitrogen
what was known about the differences with 15N and 14N
15 was heavier so DNA would settle lower down the tube 14 n would settle at top of tube
Describe the structure of DNA
Double helix
Nucleotides held together by phosphodiester bonds
Bases held by H bonds
Polymer if nucleotides
Each nucleotide made of deoxyribose, phosphate and base
Describe how a phosphodiester bond is formed between two nucleotides
Condensation reaction
Between phosphate and deoxyribose
Catalysed by DNA polymerase
Explain the process of DNA separation
DNA helicase seperates the two strands
Breaking apart H bonds between bases
What does DNA polymerase do
Joins adjacent nuclotides
Catalyst for condensation reactions
Catalyses formation of phosphodiester bonds
What is the role of single stranded DNA fragment?
Template for DNA replication
Determines order of nucleotides
What is the role of DNA nucleotides?
Contains bases for complementary base pairing
What two features of DNA help it with semi-conservative replication
Contains H bonds which allows strands to be separated
Has Two strands and both can act as templates
Describe the role of the 2 enzymes in semi conservative replication
DNA helicase breaks apart H bonds
Dna polymerase joines adjacent nucleotides
Forming phosphodiester bonds
How is a gene a code for the production of a polypeptide?
Base sequence triplets
Time in sequence of amino acids
How does the phosphodiester form between two nucleotides within DNA?
During condensation reaction the bond forms between phosphate group and deoxyribose.
It’s catalysed by DNA polymerase.
