DNA structure and replication Flashcards
Describe the structure of DNA
Molecules are double stranded and twist into a double helix shape. A subunit is called a nucleotide and consists of a phosphate, deoxyribose sugar, and nitrogenous base.
What does the backbone of DNA consist of
Sugar-Phosphate backbone held together by strong chemical permanent bonds
Explain complementary base pairing
Nucleotides on one strand form weak hydrogen bonds with nucleotides on the other strand. The base pair rule is Adenine with Thymine and Cytosine with Guanine.
What are complementary DNA strands described as
Anti-parallel as their backbones run in opposite directions.
What three things are required for DNA replication
Primers, DNA polymerase and free nucleotides
Why is there a leading strand and a lagging strand
Due to the anti-parallel structure of DNA, one strand runs 5’ to 3’ and the other runs 3’ to 5’. Primers can only bind to the 3’ end and so on the leading strand, DNA polymerase can add nucleotides continuously, while on the lagging strand must add the nucleotides in fragments.
what enzymes joins the fragments of the lagging strand together
Ligase
What is PCR
Polymerase-chain reaction used to amplify DNA
Three example of when PCR is required to amplify DNA
Settle paternity suits, solve crimes and diagnose genetic disorders
Step 1 of PCR
Temp between 92-98 degrees, to seperate the strands
Step 2 of PCR
Cooled to 50-65 degrees, primers anneal (bind to target sequences)
Step 3 of PCR
Heated to 70-80 degrees for heat tolerant DNA polymerase to begin replicating DNA
What can the process of DNA replication be described as
Semi-Conservative, as two strands of DNA are produced, consists of both a template and a new strand.
