Structure and replication of DNA Flashcards
The base sequnece of DNA form
the genetic code
What is DNA made up of
two strands of nucleotides twisted into a double helix
What are DNA nucleotides composed of
a deoxyribose sugar, a phosphate and one of four bases
What do the sugar and the phosphate form
the backbone of a DNA molecule
What are the complementary base pairs joined by
hydrogen bonds
What does the double helix have
two antiparallel strands as their 5’ to 3’ carbons run in opposite directions
What is found on the 3’ end of each strand
deoxyribose
What is found on the 5’ end of each strand
Phosphate
Where is deoxyribose found
the 3’ end of each strand
Where is phosphate found
5’ end of each strand
What happens prior to cell division
DNA replicates
What are the steps pf DNA replication
dna molecule unwinds
dna strands seperate hdyorgen bodns between the bases break
primers bind to template dna strands to provide the starting 3’ end
free dna nucleotides line up with their complementary base pair
each nucleotide is added to the 3’ end of the adjacent nucleotide by dna polymerase
replication proceeds in the 5’ to 3’ direction
What are the 3 rules for DNA replication
A DNA nucleotide can only be added to carbon 3 of another DNA nucleotide
Replication proceeds in the 5’ to 3’ direction
new strand and parallel strand must be anti parallel
What joins the fragments of DNA on lagging strand
Ligase
What are the 5 things needed for DNA replication
DNA parent molecule template strands
four types of free DNA nucleotides
enzymes
ATP for energy
Primers
What is the strand that can grow continuously called
Leading strand
What is the function of DNA polymerase
To add DNA nucleotides to the 3’ end of the new DNA strand being synthesised
What is the function of DNA ligase
joins the fragments of DNA on lagging strand
What is a primer
a single stranded short sequence of nucleotides which bnds to template DNA strands
Name the chemical group found at the 5’ end of a DNA strand
Phosphate group
What enables the primer to bond with the parent DNA strand
complementary base pairs
What is PCR
A technique that amplifies DNA using complementary primers for specific target sequences
What can PCR amplify to help
solve crimes
settle paternity suits
diagnose genetic disorders
Describe the process PCR
DNA is heated to 95 degrees to seperate the DNA strands
Its then cooled to 55 degrees to allow primers to bind to the target sequence of DNA
It is then heated to 75 degrees for heat tolerent DNA polymerase to emplify the target region of DNA
DNA polymerase adds nucleotides to the 3’ end of the primers
repeated cycles of heating and cooling amplify the traget region of DNA
What is needed to copy a DNA fragment
DNA template strands
Primers
The four DNA nucleotides
DNA polymerase
What is special about the DNA polymerase that allows it to be used in PCR
it is heat tolerant
State the structural difference between the 3’ and 5’ end of a DNA strand
3’ end is the deoxyribose sugar and the 5’ end is the phosphate
State the term which describes the production fo multiple copies of DNA using PCR
Amplify
Describe the structure of DNA
DNA is double stranded helix
made of nucleotides which consist of a deoxyribose sugar phosphate and a base
each DNA has a sugar phosphate backbone
the four bases are adenine thymine guanine and cytosine
DNA has complementary base pairing
the two DNA strands are held togetehr by hydogrne bonds between the bases and have an antiparallel structure
What is the leading strand
Is synthesised continuously towards replication fork
What is the lagging strand
Syntheised in fragments away form the replication fork
