1B-more biological molecules Flashcards
what are DNA and RNA both a type of
nucleic acid
what is teh DNA
deoxyribonucleic acid used to store your genetic info
what is RNA
ribonucleic acid to transfer genetic info from DNA to ribosome
what is a nucleotide structure
a pentose sugar, a base and a phosphate group
how do nucleotides join to make a polynucleotide
condensation reaction between phosphate group and the pentose sugar of another nucleotide
what bond forms between the pentose sugar and phosphate group in a polynucleotide
phosphodiester bond
what is the sugar-phosphate backbone
the chains of phosphates and sugars
what is teh structure of dna
double helix structure
they are really long and coiled up tightly so a lot of genetic info can fit in a small space
what is teh sugar in a dna
deoxyribose sugar
what are the four different bases and which ones they pair to
adenine and thymine
cytosine and guanine
how many hydrogen bonds between adenine and thymine and cytosine and guanine
three hydrogen bonds between cytosine and guanine
two hydrogen between adenine and thymine
how does the polynucleotides being antiparallel make a double helix
they go in opposite directions tow antiparallel strands twist to form dna double helix
what is the sugar in RNA
ribose sugar
difference between RNA and DNA bases
uracil replaces thymine as base
differences between RNA and DNA
forms a single polynucleotide strand
RNA much shorter than most DNA polynucleotide
why does DNA replicate
so each new DNA molecule has half the strands from the original DNA molecule meaning there is genetic continuity between generations of cells
How does DNA replicate
the DNA helicase breaks the hydrogen bonds between the two polynucleotide strands making the helix unwind forming two single strands
each original single strands acts as a template for a new stand. free floating DNA nucleotides are attracted to their exposed complementary bases this is called compelmentary base pairing
condensation reactions join the nucleotides of the new strand together catalysed by the enzyme DNA polymerase
hydrogen bonds form between bases on the original and new strand
each new molecule contains one strand for the original DNA molecule and one new strand
what is the action of DNA polymerase
the active site of DNA polymerase is only complementary to the 3’ end of the new DNA strand so can only add nucleotides to the 3’ end. so polymerase moves down template strand in 3’ to 5’ direction but new strand made in 5’ to 3’ direction
why does the DNA polymerase on one template strand move the opposite direction to another on another templte strand
because they are antiparallel so they move in opposite directions refer to pg56
the evidence for semi conservative replication
Two samples of bacteria were grown
one containing light nitrogen and one containing heavy nitrogen
as the bacteria reproduced they took the nitrogen to help make nucleotides for new DNA so nitrogen slowly became part of the DNA
A sample of DNA was taken from each sample of bacteria and spun in a centrifuge
the DNA with the heavy nitrogen settle toward the bottom of the tube
DNA with light nitrogen settled towards the top of the tube
then the bacteria with the heavy nitrogen was put with the bacteria with the light nitrogen and left for one round of DNA replication then spun in a centrifuge
if replication was conservative the original heavy DNA would settle at the bottom and the new light DNA would settle at the top of the tube
if the DNA replication was semi conservative the new bacterial DNA molecules would contain one stand of old DNA containing heavy nitrogen and one strand form new DNA containing light nitrogen so the DNA would settle in the middle of the tube
the DNA settled in the middle so it contained heavy and light nitrogen so semi conservative replication
