Structure And Replication Of DNA Flashcards
What does the base sequence of DNA form?
The genetic code
What is DNA composed of?
DNA is composed of nucleotides containing deoxyribose sugar, phosphate and a base.
What is a nucleotide?
A nucleotide is an organic molecule composed of a nitrogenous base, a deoxyribose sugar and a phosphate group.
What forms the sugar phosphate backbone?
Strong chemical bonds between the phosphate ( 5’ ) and the deoxyribose sugar ( 3’ )
What do sugar phosphate bonds hold together?
Sequences of nucleotides that form DNA
What are the four bases on DNA?
Adenine, Thymine, Cytosine and Guanine
What are the base pairing rules on DNA?
Cytosine bonds with Guanine and Adenine bonds with Thymine
What are the complementary bases between nucleotides joined together by?
Hydrogen bonds
What is the term used to describe how both strands of DNA run in opposite directions to eachother?
Antiparallel
What is meant by antiparallel?
Antiparallel is a term used to describe how each strand of DNA runs in opposite directions ( one runs from the 5’ end to the 3’ end and the other runs from the 3’ end to the 5’ end )
What is a term to describe the structure of DNA?
Double stranded Antiparallel helix
When does DNA replication take place?
DNA replication takes place prior to cell division
What enzyme unwinds DNA
Helicase
What is the first stage in DNA replication?
The hydrogen bonds between bases are broken to form two template strands
What is a primer and what is its role in DNA replication?
A primer is a short sequence of nucleotides which binds to the 3’ end of the template DNA strand to begin replication
What enzyme replicates DNA?
DNA Polymerase
What is the function of DNA polymerase?
DNA polymerase adds DNA nucleotides, using complementary base pairing, to the deoxyribose 3’ end of the new DNA strand which is forming
Why is there a leading and lagging strand?
DNA polymerase can only add DNA nucleotides in one direction resulting in the leading strand being replicated continuously and the lagging strand replicated in fragments
What enzyme joins fragments together?
Ligase
What is PCR?
PCR ( polymerase chain reaction ) amplifies DNA using complementary primers for specific target sequences
What is the use of primers in PCR?
Primers are short strands of nucleotides which are complementary to specific target sequences at the two ends of the region of DNA to be amplified
What is PCR in terms of cycles?
PCR is repeated cycles of heating and cooling to amplify the target region of DNA
What is stage 1 of PCR?
DNA is heated to 95 degrees celcius in order to break the hydrogen bonds between strands
What is stage 2 of PCR?
DNA is cooled to 60 degrees celcius in order to allow primers to bind to specific target sequences
What is stage 3 of PCR?
DNA is heated to 75 degrees celcius in order to allow * heat tolerant * DNA polymerase to replicate the region of DNA
What are three uses of PCR?
3 uses:
Settling paternity suits
Solving crimes
Diagnosing genetic disorders
